Device intended to be placed at a height above radio transmitting and receiving equipment and the corresponding radio communication system

Abstract

A device intended to be positioned at a height above a geographical area of ​​the Earth's surface, characterized in that it comprises a surface element, oriented towards the Earth's surface and capable of transmitting an incident radio signal received from a transmitting radio device to a receiving radio device, said transmitting radio device and said receiving radio device being located in the geographical area and respectively within the direct line of sight of said device. Figure 3

Description

Title of the invention: Device intended to be placed high above radio transmitter and receiver equipment and corresponding radio communication system Technical field of the invention

[0001] The invention relates to the field of telecommunications, in particular wireless communications.

[0002] It applies in particular but not exclusively to a cellular radio communication system based on an OFDMA type access technology, as specified by the 3GPP standards body, in one of its current or future versions. Prior art

[0003] Inter-terminal communications, known as D2D (from the English, “Device to Device”), allow a transmitting radio device to transmit data to a receiving radio device without an intermediary, that is to say without going through a radio access device to a communication network, for example a base station of a cellular network, or a Wi-Fi access point. This data transmission is possible when the radio signal received by the receiving device reaches a sufficient level of quality.

[0004] Furthermore, when D2D communications share bandwidth with cellular radio communications (between a terminal device and a base station), the cellular network operator has an interest in maximizing the resources allocated to cellular radio communications. It therefore limits the number of channels allocated to D2D communications, which requires the transmitting and receiving radio devices to be very close to each other.

[0005] Furthermore, in an urban environment, the propagation of the signal emitted by radio equipment encounters numerous obstacles (buildings, street furniture, cars, etc.) which affect the quality of the radio signal and its flow rate. The presence of such obstacles harms the quality of reception and in practice reinforces the proximity constraint between two radio devices which wish to implement D2D communication.

[0006] Faced with the massive development of applications and services requiring wireless connections everywhere and between all types of objects, particularly in the case of 5G or even 6G cellular network architectures, solutions have emerged to improve the quality of these radio communications, in particular by compensating for the loss of power with distance and / or by ensuring a direct line of sight. In this respect, reconfigurable intelligent surfaces or RIS (from the English, "Reconfigurable Intelligent Surfaces") intended to be attached to various structures, such as building facades, aerial platforms or even clothing. These RIS surfaces are designed to reflect incident radio waves towards the recipient by reflecting a beam. This technology is for example described in the paper by Yuanwei Liu et al., entitled "Reconfigurable Intelligent Surfaces: Principles and Opportunities", published in the journal IEEE COMMUNICATIONS SURVEYS & TUTORIALS, VOL. 23, NO. 3, in 2021.

[0007] RISs consist of elements that contain diodes to which a modifiable bias voltage can be applied. By pre-designing multiple bias voltage levels, each diode can apply discrete phase shifts and achieve beamforming for reflected background.

[0008] A disadvantage of this technique is that focusing the beam reflected by the RIS surface towards a given area requires control, which is expensive to implement.

[0009] The invention improves the situation.

[0010] In particular, the invention meets the need to improve radio communications, in particular D2D communications, in a simpler and less expensive manner. Presentation of the invention

[0011] To this end, the invention proposes a device capable of being positioned high above a geographical area of ​​the Earth's surface, characterized in that it comprises a surface element, oriented towards the Earth's surface and capable of broadcasting an incident radio signal received from a transmitting radio equipment to a receiving radio equipment, said transmitting radio equipment and said receiving radio equipment being located in the geographical area and respectively in direct line of sight of said device.

[0012] The invention thus proposes a completely new and inventive approach to improving radio communications, which consists of placing a device high above transmitting and receiving radio equipment located within a given geographical area. It can be positioned in the air or fixed, for example to a building facade or at the top of a pylon.

[0013] Such a device is equipped with a surface element configured to reflect and diffuse the received radio waves, so that it relays radio signals emitted by the transmitter, by diffusion towards the Earth's surface, in all directions and therefore in that of the receiver. Unlike a parabola which focuses the waves it receives at one point, the surface element according to the invention diffuses the waves it receives in a plurality of directions, including that of the recipient equipment. The latter thus receives a set of diffused radio waves, the amplitudes of which are added together, which makes it possible to improve the quality and the flow rate of the radio signal.

[0014] The fact that this device is positioned at a height makes it possible to avoid the classic obstacles to the propagation of radio waves, such as buildings, street furniture, cars or any other construction linked to human activity, which would come between the transmitting radio device and the receiving radio device. Thus, with the invention, the direct line of sight situation (from the English, "line of sight") between, on one side the transmitter and the flying device and on the other side the flying device and the receiver, is guaranteed.

[0015] Furthermore, the invention makes it possible to relax the proximity constraint, which was until now very strict, between two radio devices wishing to communicate in D2D mode.

[0016] According to one aspect of the invention, the surface element is passive.

[0017] An advantage of the device according to the invention is that it does not need to be controlled or reconfigured, nor even powered to broadcast the radio waves it receives, unlike a reconfigurable smart surface RIS known from the prior art, which refocuses the radio waves towards a given point. It is therefore simple and inexpensive to implement.

[0018] Alternatively, the surface element may be active, for example capable of changing polarization, which makes it possible to direct the diffusion towards a given area.

[0019] According to yet another aspect of the invention, said surface element is made of a material having asperities whose dimensions are of the order of a wavelength of the radio signal emitted by the transmitting radio equipment.

[0020] For example, the asperities are cylindrical.

[0021] According to another aspect of the invention, the surface element is planar.

[0022] One advantage is to ensure that all reflected radio waves are broadcast to the receiving radio equipment located on the ground in the geographic area.

[0023] According to yet another aspect of the invention, the device comprises a balloon inflated by a fluid and the surface element is fixed on a lower portion of the balloon.

[0024] In this embodiment, the device according to the invention is positioned in the air. An advantage of this balloon is that it is inexpensive and relatively easy to deploy over the geographical area, for example to meet specific and temporary needs, such as high demand caused by the holding of a sporting, musical or festive event bringing together in the geographical area an increased number of users of a communication network. It can also make it possible to better cover a difficult-to-access area where radio coverage by base stations of the cellular network is insufficient. Finally, it can constitute a replacement solution in the event of a base station failure.

[0025] For example, it is an aircraft, that is to say a means of transport capable of rising and moving at altitude, within the Earth's atmosphere, almost static. tionary. It can be dirigible. Alternatively, it is fixed to the ground by one or more cables.

[0026] According to another embodiment of the invention, the device of the invention is a machine equipped with a motor which allows it to fly and maintain its position, such as for example a drone.

[0027] Correlatively, the invention also relates to a radio communication method implementing the broadcasting of an incident radio signal emitted by a transmitting radio equipment to a receiving radio equipment, said transmitting radio equipment and said receiving radio equipment being located in a geographical area of ​​the Earth's surface, by a surface element of a device positioned high above the geographical area, in direct line of sight with said transmitting radio equipment and said receiving radio equipment.

[0028] Such a method is advantageously implemented by the aforementioned device.

[0029] The invention also relates to a radio communication system comprising a radio transmitter equipment and a radio receiver equipment and the aforementioned device.

[0030] Such a system has the same advantages as the device according to the invention.

[0031] According to one aspect of the invention, in such a system, the device is positioned so that the surface element is parallel to the ground of the geographical area and equidistant from the transmitting radio equipment and the receiving radio equipment.

[0032] One advantage is to make the broadcasting of radio waves more efficient, to increase the value of the amplitude of the broadcast radio signal and therefore the flow rate of the radio communication.

[0033] According to another aspect of the invention, the transmitting radio equipment and the receiving radio equipment are terminal equipment respectively configured to communicate directly with each other.

[0034] Such a system has the advantage of facilitating inter-device communications, known as D2D.

[0035] According to yet another aspect of the invention, the transmitting radio equipment, respectively the receiving radio equipment, is a radio access equipment of a communication network and the receiving radio equipment, respectively the transmitting radio equipment, is a terminal equipment configured to connect to said radio access equipment.

[0036] Another advantage of the system according to the invention is that it also makes it possible to facilitate cellular radio communications, between a terminal device, for example a mobile telephone, and a base station or for a Wi-Fi access network between a terminal device and a Wi-Fi access point.

[0037] Of course, the different embodiments of the invention can be combined with each other. Brief description of the drawings

[0038] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an exemplary embodiment thereof without any limiting character. In the figures:

[0039] [Fig-1] schematically illustrates an example of the architecture of a system of radio communication comprising a device according to one embodiment of the invention;

[0040] [Fig.2] describes in the form of a flowchart a radio communication method implemented work by the device according to an embodiment of the invention;

[0041] [Fig.3] illustrates in more detail the use of the aerial device according to the invention for implementing a communication in D2D mode between a transmitting radio equipment and a receiving radio equipment, according to one embodiment of the invention;

[0042] [Fig.4]: details an example of a flat and rectangular surface element of the device according to one embodiment of the invention;

[0043] [Fig.5]: schematically illustrates the radio waves reflected and scattered by the surface element of the device according to one embodiment of the invention;

[0044] [Fig.6]: schematically illustrates the angles of incidence and diffusion of the radio waves received, reflected and diffused by the surface element according to an exemplary embodiment of the invention;

[0045] [Fig.7A][Fig.7B] illustrate an example of positioning of the device according to the invention with respect to the transmitting and receiving radio equipment;

[0046] [Fig.8] illustrates an example of a curve representing a distribution function cumulative CDF as a function of a percentage increase in PAD flow rate provided by the implementation of the invention. Description of the invention

[0047] The principle of the invention consists in positioning at height, above a geographical area of ​​the Earth's surface, a surface element, oriented towards the Earth's surface and capable of broadcasting an incident radio signal received from a transmitting radio equipment to a receiving radio equipment, said transmitting radio equipment and said receiving radio equipment being located in the geographical area and respectively in direct line of sight or LOS (from the English, "Line of Sight") of said device.

[0048] This surface element is for example fixed to a device capable of being stationed in the air, called aerial, such as an aerial platform or an aircraft or even an unmanned aerial vehicle of the UAV type (from the English, “Unmanned Aerial Vehicle”). It can alternatively be fixed to a facade of a building or to a pylon.

[0049] In relation to [Fig. 1], an example of a device is presented for illustrative purposes UAD according to the invention, in its environment.

[0050] This is an aircraft, of the balloon type, inflated with a fluid lighter than air, for example helium. It can be dirigible or connected to the ground by cables (not shown). In this example, it is stationed above a geographical zone ZG at a height H, for example equal to 50 m. This height guarantees its direct visibility from transmitting and receiving radio equipment located in the zone ZG, despite the presence of obstacles OB, such as buildings or other structures.

[0051] According to the invention, this UAD device comprises in its lower part, a surface element SE oriented towards the ground. Advantageously, this surface element SE is flat. For example, it is rectangular in shape and has a width and length of the order of a few meters.

[0052] Advantageously, this surface element is, for example, made of a rough material, which has cylindrical asperities whose radii are of the order of the wavelength of a radio signal emitted by a radio transmitting equipment. An example of a material making it possible to reflect any incident radio signal received by diffusing it in all directions is described in the recommendation document entitled "Effects of building materials and structures on radio wave propagation above about 100 MHz-P Series-Radiowave", published in 2015 by the ITU under the reference ITU-R P.2040-1, in section 2.3.2.

[0053] In [Fig.l], examples of transmitting and receiving radio equipment UE1, UE2, BS are also shown. These equipments are configured to transmit and receive radio signals transmitted at a given radio wavelength. These are, for example, terminal equipments UE1, UE2, for example user equipments of the mobile telephone type of the smartphone type (in English, "smartphone"), or even laptops, tablets or connected objects of the Internet of Things or loT (from the English, "Internet of Things"). Such terminal equipments are configured to connect to radio access equipment of a communication network, for example a base station BS, according to a cellular access technology of the ODFMA type as specified by the 3GPP in one of its current (LTE-A, 5G) or future (6G and following) versions, or to another type of access point (not shown), based on Wi-Fi technology for example.

[0054] It is assumed here that the terminal equipments UE1, UE2 are also configured to communicate directly with each other, in D2D mode, notably but not exclusively, using frequencies (or wavelengths) allocated to cellular networks. However, as illustrated by [Fig.l], UE1 and UE1 are not in direct line of sight because of the obstacle constituted by the building OB.

[0055] In [Fig.l], there is finally shown a radio communication system S according to the invention, comprising the aerial device UAD and at least the radio equipment transmitter UE1 and the radio receiver equipment UE2. Of course, one of the radio equipments (transmitter or receiver) can be the base station BS. In this system, said aerial device UAD is positioned in the air so that said transmitting radio equipment and said radio receiver equipment are respectively in direct line of sight with it.

[0056] In the example of [Fig.l], the transmitting radio equipment UE1 transmits an incident radio signal IS intended for the receiving radio equipment UE2. Its transmission is partly blocked by the building OB, but it is assumed that at least part of the incident signal reaches the surface element SE of the aerial device according to the invention, which reflects it and diffuses it in a plurality of directions. Part of the diffused signals DS is received by the receiving radio equipment UE2.

[0057] In relation to [Fig. 2], a radio communication method according to the invention is now described. Such a method is for example implemented by the device UAD of [Fig. 1]. It comprises the reflection and diffusion 21 of the incident radio signal IS emitted by the transmitting radio equipment UE1 into a broadcast radio signal RS in a plurality of directions including that of the receiving radio equipment UE2.

[0058] In relation to [Fig. 3], two transmitting and receiving radio equipments are now described, for example, the terminals UE1, UE2 of [Fig. 1], which wish to use a given service, for example streaming audiovisual content, requiring a bit rate T. It is assumed that, given their environment, the propagation of a radio signal between the transmitting radio equipment UE1 and the receiving radio equipment UE2 is highly disturbed, particularly in an urban environment, in particular because of the presence of buildings and street furniture such as the building OB. Consequently, the quality of service and the bit rate of the communication may be degraded.

[0059] The transmitting equipment UE1 transmits an incident radio signal IS intended for the receiving equipment UE2. It is assumed that it comprises a beam of radio waves transmitted in a plurality N, with N being a non-zero integer, of directions. O denotes the center of the surface element SE and ri denotes the distance between the transmitting equipment UE and this center O. Correspondingly, r2 denotes the distance between the center O and the receiving equipment UE2. It is assumed that the equipments UE1 and U2 are distant by r.

[0060] It is now a question of showing that the use of the aerial device UAD according to the invention, equipped with a diffusing surface SE placed in direct line of sight LOS respectively with the transmitting equipment UE and the receiving equipment UE2 and placed at the height H, for example equal to 50m above a geographical zone ZG comprising UE1 and UE2, makes it possible to improve the propagation of the signal between the two pieces of equipment and in particular to maintain the flow rate of the communication and the quality of required service.

[0061] To do this, we first consider an expression of the flow rate of a radio communication between UE1 and UE2 in D2D mode, in the general case (without the use of the device according to the invention).

[0062] The flow rate is written as follows:

[0063] T= W log2(l+ YD2D Y*d2d / (Nth + Poth)) (Eq. 1)

[0064] Where W denotes the bandwidth, Pt the power transmitted by UE1, Yd2d the amplitude of the signal received by UE2, Y*d2d the complex conjugate of Yue2j Poth the power due to interference, N* the thermal noise.

[0065] In general, the power Pr received by a receiving device from a transmitting device transmitting a power Pt can be written:

[0066] Pr = = KPf\ where K is a constant and q is the pathloss parameter.

[0067] The constant K depends on the radio frequency and q depends on the propagation environment (urban, rural, etc.). The value of q is between 2 and 4. In free space, q=2, as indicated in the ITU recommendation document, published in November 2016 and entitled “Calculation of free space attenuation”, under the reference ITU-R P 525-3.

[0068] The amplitude of the signal directly received by the receiving radio equipment UE2 from the transmitting radio equipment UE1 is written as follows: YD2D = (Eq. 2) Or 4 _ , (Eq. 3) r is the distance between UE1 and UE2, Guei, &UE2 the respective gains of the transmitting and receiving radio equipment UE1, UE2. ^D2D ~ KUE\UE2-&UEA-GUE2, Pt the power transmitted by UE1,

[0069] £ = ^L^ is the wavelength with 2 = y, c the speed of light and f the frequency radio waves,m = 2æ / , eX.KUEWE2 a constant.

[0070] In relation to [Fig.4], we consider more precisely a planar and rectangular surface element SE of surface P, of half length L and half width 1. By example L=l=10m.

[0071] The diffusing surface of the surface element SE according to the invention reflects and diffuses the radio waves that it receives at all points Mj of the surface P in all directions, in particular in the direction of the device UE2.

[0072] Thus, as illustrated by [Fig.5], the diffusing surface element SE of the device UAD according to the invention receives the radio waves Dpi, Dp2... Dpj .. .DPN, with N non-zero integer from the transmitting radio equipment UE1. They are reflected and diffused by the surface element in all directions. As for the device UE2, it receives the radio waves Dp' 1, Dp'2...Dp'j...Dp'N from the surface element SE.

[0073] We now designate by Y^ris the amplitude of the signal diffused by the diffusing surface P of the element SE, and received by UE2: Ynris = E ) (eq. 4), J ] rjr'J OR kNRIS~

[0074] 2 is the wavelength with 2 = —, c the speed of light and f the frequency of radio waves,« = 2æ / Gs is the gain of the diffusing surface, t the time, ri r2.. .q r'N, with j non-zero integer, are the respective distances (between UE1 and the surface SE) of the radio waves or rays Dpj coming from UE1 and arriving on the surface SE, r'ir'2...r'j rN are the respective distances (between the surface SE and UE2) of the radio waves or rays DPJ- diffused by the surface SE and reaching UE2.

[0075] The scattering of rays coming from UE1 is done by each infinitesimal surface element of the surface SE.

[0076] We have:

[0077] y - ANRIS.eiœt~kr^e^^ Ye'h(P+GjjGu. m2 v2) (Eq- 5) iViUû Lxi.ij XP Zz \ l7 Z /

[0078] With ANRIS - F ( lt 1' w2 ) = {ert ( ^ui ) ' ert ( ^u2 / ) G(«» “2)=6) where q

[0079] \ < 2 fm mi , erf being an error function known per se, called ert ( qu = 1 - -f- Gaussian error function.

[0080] In relation to figure 6, we consider the angles a, fi of arrival of a wave incident wave Dpi or F] (emitted by UE1) at point O, located at the center of the surface SE. a', fi' are the scattering angles of this incident wave Dpi into a scattered wave D'p2 or K, respectively with the vertical axis Oz and the horizontal axis Ox.

[0081] We have:

[0082] a_ ( )

[0083]

[0084] = / r=\K,x)-

[0085] We also have:

[0086] y = cosa - cosa

[0087] - Cos^ - cos / ?

[0088] ü = l(2L + ±)

[0089] u = z + dy

[0090] v = z + _Lf

[0091]

[0092] W2 = L + £y

[0093] v-.l+^C

[0094] u=l + ^.

[0095] We note Let be a vector UEXm with any P°'nt Mj of the surface P of the element SE. We have:

[0096] + z + x= Tj, (Eq. 7) where 7 and * represent the projections of rÿ on the Oz and Ox axes respectively.

[0097] We designate by Xj and Zj the coordinates of Tj on the axes Ox and Oz.

[0098] We can write: rp = + zy + xf + ir^-cosa + 2j\Xj£Xiï$ + 2^^cos ( z, xj

[0099] And so:

[0100] ,.^ri2|1+2^-+^ + ^P^8) 'j '1 r; — r, — r|2 j

[0101] We assume here that <1 and we make a limited development of} j as follows: r, = rj + 2.^ z ..cos ( a ) +2.jx ,cos ( P ) JJ 2r{

[0102] It is noted that the following condition is satisfied as an example for a surface element SE of dimensions L = 10m and l=10m and a device UAD located at a height H=50m, since rl>7m.

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] [YES]

[0112]

[0113]

[0114]

[0115]

[0116]

[0117]

[0118]

[0119] Since cos j =0, we have: rj=r. + Z..cos (a) +xy.cos ( / 5) (Eq. 9) D 2 / d We do a similar reasoning for fj and we obtain: fj = r2 - W 10) We can therefore write: rj +r = rt + r2 + z / :os ( « ) +.17COS ( / J ) --^.cos ( to ) -x ,.cos ( fi ) The diffusing surface element SE according to the invention is considered here as a continuum of diffusing elements, which makes it possible to establish an expression for the discrete sum of the radio waves received by the receiving equipment UE2, as an integral and to establish the expression for the flow rate. Indeed, we can write: au^+auv2-—; Ç ) dzdx Y — — INRIS~ r (Eq. 12) With: . . Y2 , (-1)3 / 4. (Eq. 13) G(uv ih) = \ve-ika“v2d With the invention, the amplitude YD2D of the radio signal emitted by UE1, directly received by UE2 and the amplitude YNRls of the radio signal emitted by UE1 and broadcast by the surface element SE are added. It follows that the flow rate T' of the radio communication in D2D mode between UE1 and UE2 in the presence of the device according to the invention can be expressed as follows: T'= W'.log2(l+ (YD2D+YNRls)(YD2D+YNRls))* / (Nth + Poth))) (Eq. 14). The YNR1S amplitude therefore increases the T' flow rate value and therefore improves the quality of D2D radio communication. In view of what has been described previously and the expression of the amplitude YNR1S, we understand that the value of the flow rate T' depends on the relative positions of the aerial device UAD and the radio transmitter UE1 and receiver UE2 equipment. According to an embodiment of the invention, illustrated by Figures 7A and 7B, we consider the case where the device UAD is positioned so that its surface element SE is included in a plane parallel to the ground of the geographical zone ZG and equidistant from UE1 and UE2. As a result, the angles a and a' are equal. The same is true for / ? and / f'. As a result, l and f are equal. We therefore have Ui=-L, u2=L, Vi=-H and v2

[0120] It can be shown that the expressions (erf ( qu ) - erf qu? and erf^p'J -erf(^ are maximized, and that it is therefore the same for F(ui,u2) and G(vbv2).

[0121] Consequently, this configuration of the surface element SE relative to the ground makes it possible to increase the value of the amplitude YNR1S of the signal diffused by the surface element SE and therefore the flow rate T'. Intuitively, it is understood that it makes it possible to make the diffusion of radio waves by the surface element more efficient and to minimize the path traveled by the incident and diffused waves.

[0122] It can be shown that this particular case allows to maximize the value of the amplitude YNR1S. In relation to [Fig.7B], we first consider the orthogonal projection Op of the UAD device on the ground. In general, the points Op, UE1 and UE2 form an isosceles triangle at Op. We now consider the projection Op' of Op on the axis O'x connecting the radio equipment UE1 and UE2. The line (OpOp') is the mediator of the segment UE1UE2. We therefore have UElOp = OpUE2=r / 2.

[0123] By deriving the expression of YNRls as a function of a variable xp corresponding to the abscissa of the orthogonal projection of the UAD device on the ground, we obtain a zero value for xp=r / 2, which corresponds to a maximum value of YNR1S.

[0124] Of course, the invention is not limited to this particular example. On the contrary, as proven by the expression of YNRls(equationl2) established in the general case, the throughput T' of the radio communication is always improved by the presence of the device UAD according to the invention above the geographical zone ZG where the radio equipment UE1 and UE2 are located.

[0125] Resource allocation

[0126] In a current mobile communication network, the number of D2D communications that can take place simultaneously between radio equipment located in a given geographical area is limited by the network operator and determined by the number of channels required to provide the service requested by the equipment UE1 and UE2. Furthermore, the number of channels that can be allocated to a D2D communication is linked to the available bandwidth. Thus, the number of simultaneous communications is extremely limited.

[0127] It is now assumed that the bandwidth W available for D2D radio communication between UE1 and UE2 is defined by a given number of channels Ne, each channel being associated with a bandwidth Wc, less than W.

[0128] We have: W= Nc.Wc, with Wc the bandwidth allocated to each channel.

[0129] Considering the conditions of a communication system implementing one or more D2D communications, such as the relative positions of the equipment radio transmitter UE1 and radio receiver UE2, the radio wave propagation environment and the disturbances it generates, etc.), the number of channels allocated to the UE1, UE2 equipment so that they can use the service they request, depends on the required bit rate T.

[0130] Starting from the previous equation 1, we obtain in the general case and without resorting to an aerial device UAD according to the invention:

[0131] T' = Nc.Wc.log2(l+ YD2D Y*d2d / (Nth + Poth)) (Eq. 1')

[0132] On the other hand, with the invention, the expression of the flow rate T becomes:

[0133] T'= Nc'.Wc log2(l+ (YD2D+YNRIS)(YD2D+YNRIS))* / (Nth + Poth))) (Eq. 1”)

[0134] It is assumed that, taking into account the loss of power of the direct signal due to the environment, received by the radio receiving equipment UE2: YD2D«YNR1S.

[0135] We therefore have:

[0136] log2(l+ (YD2D+YNRIS)(YD2D+YNRIS)m Nth + Poth))) * log2(l+ (YNRls)(YNRls)* / ( Nth + P oth)))

[0137]

[0138] Now, the log2 function being increasing, we deduce:

[0139] log2(l+ (YNR1S)(YNR1S)*) / ( Nth + Poth)))> log2(l+ YD2D Y*d2d / (N* + Poth))

[0140] It follows that Nc' <nc.

[0141] The use of the device according to the invention therefore makes it possible to reduce the number of channels to be allocated to D2D radio communication between UE1 and UE2.

[0142] In relation to [Fig.8], a measurement of the throughput improvement provided by the UAD aerial device according to the invention is now presented. This is a curve representing a cumulative distribution function on the ordinate and a percentage increase in throughput on the abscissa. It concerns the case of a device placed at a height of 50 m with an available bandwidth of 1 MHz. The transmission power of the transmitting radio equipment is 1 W. This curve illustrates the fact that the invention can make it possible to multiply the throughput of a D2D communication by up to a factor of 3.

[0143] The invention which has just been described has numerous advantages. It responds in particular to a temporary and local demand for improving radio communications between radio equipment located in a geographical area. Indeed, it can be used on the occasion of various events, for example sporting or festive events, which bring together a larger audience than usual in the geographical area in question. It makes it possible to improve D2D communications between user equipment and therefore to respond to an increased need in terms of the number of radio communications.

[0144] Alternatively, it can also be used as a replacement for one or more base stations when they are temporarily unavailable following a breakdown, for example. In this case, one or other of the transmitter and receiver radio equipment described above cededly is a base station.

Claims

Claims

1. Device (UAD) intended to be positioned high above a geographical area (ZG) of the Earth's surface, comprising a surface element (SE), oriented towards the Earth's surface and capable of broadcasting an incident radio signal (IS) received from a transmitting radio equipment (UE2) towards a receiving radio equipment (UE2), said transmitting radio equipment and said receiving radio equipment being located in the geographical area and respectively in direct line of sight of said device, characterized in that said surface element is made of a material having asperities whose dimensions are of the order of a wavelength of the radio signal transmitted by the transmitting radio equipment.

2. Device according to the preceding claim, characterized in that the surface element is passive.

3. Device according to any one of the preceding claims, characterized in that the surface element is planar.

4. Device according to any one of the preceding claims, characterized in that it comprises a balloon inflated by a fluid and in that the surface element is fixed on a lower part of the balloon.

5. A radio communication method, characterized in that it comprises the broadcasting (21) of an incident radio signal (IS) emitted by a transmitting radio equipment (UE1) to a receiving radio equipment (UE2), said transmitting radio equipment and said receiving radio equipment being located in a geographical area (ZG) of the Earth's surface, by a surface element of a device positioned high above the geographical area, in direct line of sight with said transmitting radio equipment and said receiving radio equipment, characterized in that said surface element is made of a material having asperities whose dimensions are of the order of a wavelength of the radio signal emitted by the transmitting radio equipment.

6. Radio communication system (S) comprising a transmitting radio equipment (UE1) and a receiving radio equipment (UE2), characterized in that it further comprises a device according to any one of claims 1 to 4.

7. Radio communication system according to the preceding claim, characterized in that the device (UAD) is positioned so that the surface element is parallel to the ground of the geographical area (ZG) and equidistant from the transmitting radio equipment and the radio equipment receiver.

8. Radio communication system, according to any one of claims 6 to 7, characterized in that the transmitting radio equipment and the receiving radio equipment are terminal equipment respectively configured to communicate directly with each other.

9. Radio communication system according to any one of claims 6 and 7, characterized in that the transmitting radio equipment, respectively the receiving radio equipment, is a radio access equipment (BS) of a communication network and the receiving radio equipment, respectively the transmitting radio equipment, is a terminal equipment configured to connect to said radio access equipment.

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