FR3095097A1 - Method and device for controlling a data transmission mode used by a vehicle to communicate - Google Patents

Abstract

Method of controlling and device for controlling a mode of data transmission intended for use by a vehicle The control method enables a controller to control a mode of data transmission intended for use by a first vehicle to communicate with a second vehicle and with a third device, this method comprising: a step of determining (E30, E60) whether a condition is verified, said condition being a C1 condition if, when the first vehicle is in full-duplex mode, a flow rate of data transmission between the first vehicle and the second vehicle is less than or equal to a data transmission rate between the first vehicle and the third communication device, and a condition C2; and - if said condition is verified, a step of activating (E50) a full-duplex data transmission mode at the first vehicle to communicate with the second vehicle and with the third device. Figure for the abstract: Fig. 4.

Description

Method and device for controlling a data transmission mode used by a vehicle to communicate

The invention relates to the general field of telecommunications. It relates more particularly to communications in a wireless communications network, in which the devices connected to the network have the possibility of communicating with each other peer-to-peer.

Peer-to-peer communication between two devices means the exchange of data between these two devices without going through a central server. No limitation is attached to the type of data exchanged between the devices (voice, text, etc.) during such peer-to-peer communication, nor to the connectivity technology used by the devices to detect the presence of devices neighbors and connect with each other for peer-to-peer communication. Devices may use Bluetooth connectivity, WiFI (Wireless FIdelity), WiFI Direct, LTE (Long Term Evolution), etc.

Peer-to-peer communications are of great interest today. For example, they have shown their effectiveness in providing resilient communication services in cases of voluntary or unintentional disruption of traditional communication networks; they can also be used to offload traditional communication networks, or to protect against cyber-surveillance, etc.

In the context of the invention, we are more particularly interested in communications between two vehicles (in other words two devices likely to be in motion), and a third device, which can be another vehicle or a base station (ie an access point) of a cellular communications network. The vehicles considered are for example land vehicles such as cars or trains, airborne vehicles such as drones, etc. Consider more specifically the situation illustrated in FIG. 1 in which a vehicle V20 transmits (and/or receives) data to (and/or from) another vehicle V30 via a vehicle V10. Such a situation may arise in particular when the vehicle V20 needs to transmit data to the vehicle V30 but the quality of the signal it receives from the latter is insufficient, or even when the vehicle V10 wishes to transmit data to the vehicle V30 but needs, to transmit this data, data held by the V20 vehicle. It is assumed in the example considered in FIG. 1 that the vehicles V10, V20 and V30 are, for example, cars in motion. These examples are of course not limiting in themselves and given solely by way of illustration.

In the state of the art, the transmission from V20 to V10 and the transmission from V10 to V30 cannot be done simultaneously using the same radio resource, typically the same frequency of a spectrum used by vehicles to communicate peer- at-even. In other words, the V10, V20 and V30 vehicles are configured to operate according to a so-called half-duplex data transmission mode, more commonly called "half-duplex", making it possible to limit the level of interference suffered by the vehicles and not not degrade the quality of the signal received by them.

The V10 vehicle therefore cannot receive data from the V20 vehicle and simultaneously transmit data (for example, that which it receives from the V20 vehicle as it receives it or data derived from the data received from the V20 vehicle ) to vehicle V30 on the same frequency. It follows that the performance of the peer-to-peer network thus formed, in particular in terms of throughput and spectral efficiency, is not optimized.

The same is true if instead of considering a V30 vehicle, another device is considered, such as for example a base station of a cellular wireless communications network.

The invention aims to improve the situation described previously and to make better use of the resources of the network formed by the various equipment considered.

To this end, it proposes a control method, by a controller, of a data transmission mode intended to be used by a first vehicle to communicate with a second vehicle and with a third device, this method comprising:

- a step of determining whether a condition is verified, said condition being:

● if when the first vehicle is in full-duplex mode, a data transmission rate between the second vehicle and the first vehicle is less than or equal to a data transmission rate between the first vehicle and the third device, a condition C1 such as :

µ _FD,1,1 < µ ₀ /[exp(1/(B+C)-1]-1

with µ ₀ = P ₂ ⁽¹⁾ /(I _oth +N _th ), B=1/log(1+ µ _HD,1,2 )) and C=W2/[W1.log(1+µ _{HD,3 ,1} ))] where:

μ _HD,1,2 is a signal-to-interference-plus-noise ratio (SINR) received at the level of the first vehicle when the first vehicle, in half-duplex mode, receives a volume VOL2 of data from the second vehicle;

μ _HD,3,1 is a SINR received at the level of the third communication device when the first vehicle, in half-duplex mode, transmits a volume VOL1 of data to the third device;

P ₂ ⁽¹⁾ designates the power of the volume VOL2 of data received by the first vehicle and transmitted by the second vehicle;

W1 and W2 respectively designate passbands of the transmission channels between the first vehicle and the third device, and between the second vehicle and the first vehicle;

I _oth is an interference level generated at the level of the first vehicle by at least a fourth device transmitting data on a radio resource on which simultaneously, the first vehicle, in full-duplex mode, transmits the volume VOL1 of data to the third communication device and receives the volume VOL2 of data from the second vehicle or on which simultaneously the first vehicle, in half-duplex mode, receives the volume VOL2 of data from the second vehicle; and

N _th is a noise level received by the first vehicle;

● otherwise a condition C2 such that:

_µFD,3,1 > exp(1/A)-1

with A=αB+(W1/W2)C and α=VOL2/VOL1 and where µ _FD,3,1 is the SINR received at the level of the third device when the first vehicle, in full-duplex mode, transmits the volume VOL1 of data to the third device on a radio resource and simultaneously receives on this resource the volume VOL2 of data from the second vehicle;

- if said condition is verified, a step of activating a full-duplex data transmission mode at the level of the first vehicle to communicate with the second vehicle and with the third device.

Correlatively, the invention also relates to a controller configured to control a data transmission mode used by a first vehicle to communicate with a second vehicle and with a third device, this controller comprising:

- a determination module, configured to determine whether a condition is verified, said condition being:

● if when the first vehicle is in full-duplex mode, a data transmission rate between the second vehicle and the first vehicle is less than or equal to a data transmission rate between the first vehicle and the third device, a condition C1 such as :

µ _FD,1,1 < µ ₀ /[exp(1/(B+C)-1]-1

with µ ₀ = P ₂ ⁽¹⁾ /(I _oth +N _th ), B=1/log(1+ µ _HD,1,2 )) and C=W2/[W1.log(1+µ _{HD,3 ,1} ))] where:

μ _HD,1,2 is a signal-to-interference-plus-noise ratio (SINR) received at the level of the first vehicle when the first vehicle, in half-duplex mode, receives a volume VOL2 of data from the second vehicle;

μ _HD,3,1 is a SINR received at the level of the third communication device when the first vehicle, in half-duplex mode, transmits a volume VOL1 of data to the third device;

P₂ ⁽¹⁾ denotes the power of the volume VOL2 of data received by the first vehicle and transmitted by the second vehicle;

W1 and W2 respectively designate passbands of the transmission channels between the first vehicle and the third device, and between the second vehicle and the first vehicle;

I _oth is an interference level generated at the level of the first vehicle by at least a fourth device transmitting data on a radio resource on which simultaneously, the first vehicle, in full-duplex mode, transmits the volume VOL1 of data to the third device and receives the volume VOL2 of data from the second vehicle or on which simultaneously the first vehicle, in half-duplex mode, receives the volume VOL2 of data from the second vehicle; and

N _th is a noise level received by the first vehicle;

● otherwise a condition C2 such that:

_µFD,3,1 > exp(1/A)-1

with A=αB+(W1/W2)C and α=VOL2/VOL1 and where µ _FD,3,1 is the SINR received at the level of the third device when the first vehicle, in full-duplex mode, transmits the volume VOL1 of data to the third device on a radio resource and simultaneously receives on this resource the volume VOL2 of data from the second vehicle;

- an activation module configured to activate if said condition is verified, a full-duplex data transmission mode at the level of the first vehicle to communicate with the second vehicle and with the third device.

The invention advantageously applies whether the third device is a vehicle or any other equipment able to communicate peer-to-peer with the first vehicle, or whether it is an access point (ie a base) of a wireless communications network connected to the first vehicle.

In addition, in a particularly advantageous manner, the third device can also be, in a particular embodiment, the second vehicle. In other words, in this embodiment, there is two-way data communication between the first and the second vehicle, and the two vehicles are then capable of operating in full-duplex mode.

In a preferred example of application of the invention, the data transmitted by the first vehicle to the third device comprises the data (in original or modified form) transmitted by the second vehicle to the first vehicle (they may moreover comprise other data at an additional cost). This example models the case where the first vehicle acts as a relay to the third device for the second vehicle to transmit its data, if the third device is distinct from the second vehicle. It should be noted that the invention can also be applied in other contexts, including when the data transmitted by the first vehicle to the third device comprises only part of the data received from the second vehicle (in original or modified form) and/ or data different from that received from the second vehicle. It is however assumed that the volume of data transmitted by the second vehicle to the first vehicle is less than or equal to the volume of data transmitted by the first vehicle to the third device.

In a known manner, a "full-duplex" mode, or full duplex, of data transmission is a mode of data transmission in which the data circulates at the level of the devices implementing this mode of transmission in a bidirectional and simultaneous manner: thus each device can transmit and receive data simultaneously using the same radio resource, for example the same frequency or the same frequency band. When the first vehicle is configured according to a full-duplex transmission mode, it can therefore receive data from the second vehicle on a radio resource (eg on a given frequency) and simultaneously transmit data to the third device on this same radio resource .

This makes it possible to speed up the data transmission time from the second vehicle to the third device via the first vehicle while conserving radio resources due to the simultaneous use of the same radio resource. The spectral efficiency obtained is thus improved compared to the state of the art where only a half-duplex transmission mode is envisaged.

Furthermore, the energy efficiency at the level of the first vehicle is also increased: the time during which the first vehicle must remain active to receive data from the second vehicle and transmit data to the third device is reduced in full-duplex mode, which allows the first vehicle to reduce its energy consumption (and thus save its energy resources).

To achieve this result, the invention advantageously activates the full-duplex data transmission mode at the level of the first vehicle when a controller determines that a predefined condition, which is chosen from among the aforementioned conditions C1 and C2, is verified. The conditions C1 and C2 have been advantageously defined by the inventors to guarantee that the transmission time necessary when the full-duplex mode is activated at the level of the first vehicle, to route data from the second vehicle to the first vehicle and from the first vehicle to 'to the third device is less than the corresponding transmission time required when the first vehicle operates in half-duplex mode, and this without sacrificing the performance achieved during this transmission in terms of error probability. The inventors have indeed used to derive the two conditions C1 and C2, the Shannon relation giving the capacity of a channel as a function of the signal-to-interference-plus-noise ratio (SINR) on this channel. However, in a manner known per se, the capacity of a channel designates the upper limit of the data rate which can be transmitted reliably on this channel, that is to say with an error probability which tends towards zero. . Note that the conditions C1 and C2 are defined for a volume

Thus, the full-duplex transmission mode also making it possible to save radio resources and achieve better spectral efficiency, this means that when one of the conditions C1 or C2 is verified, there is every interest in activating the full-duplex mode at the level of the first vehicle as proposed by the invention, since the performances are optimized at all levels (time saving, spectral efficiency gain and energy saving at the level of the first vehicle).

No limitation is attached to the way the controller determines whether the condition C1 or C2 is verified or not. This can be for example by evaluating and comparing the SINRs or the ratios involved in these conditions, by demonstrating the inverse relationships, by considering approximations of the terms of these conditions, etc.

In a particular embodiment, the determination step is reproduced at different instants.

These different instants can be separated by a regular period of time, in other words, the controller re-evaluates the predefined condition C1 or C2 periodically, or even quasi-continuously if the chosen period of time is relatively short. This makes it possible to adapt to the changing conditions likely to be experienced by the various moving equipment considered (first, second and, where applicable, third vehicle) and to reassess at different times the advisability of activating the transmission mode in full -duplex at the level of the first vehicle. Indeed, the first and second vehicles being in motion, as well as possibly the third device depending on the context envisaged, the different quantities evaluated in the context of the invention (SINR and other ratios) are likely to vary as a function of time, in particular depending on the speed of the vehicles.

As a variant, the different instants at which the determination step is reproduced can correspond to the detection by the controller of predetermined events, such as for example the detection of a peer-to-peer communication between new vehicles, etc.

It can also be envisaged that if the controller determines that the condition C1 or C2 depending on the specific case is no longer verified at a given instant or over a given period of time while the first vehicle is in full-duplex mode , to deactivate this full-duplex mode at the level of the first vehicle and to reactivate a half-duplex transmission mode.

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

The invention thus also relates to a computer program on a recording medium, this program being capable of being implemented in a computer or more generally in a controller in accordance with the invention. This program includes instructions adapted to the implementation of a control method as described above.

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 partially compiled form, or in any other desirable form.

The invention also relates to an information medium or a recording medium readable by a computer, and comprising instructions of the computer program as mentioned above.

This information or recording medium can be any entity or device capable of storing the programs. For example, the media can comprise a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or else a magnetic recording means, for example a hard disk or a flash memory.

On the other hand, the information or recording medium may be a transmissible medium such as an electrical or optical signal, which may be routed via an electrical or optical cable, by radio link, by wireless optical link or by other ways.

The program according to the invention can in particular be downloaded from an Internet-type network.

Alternatively, the information or recording medium may be an integrated circuit in which a program is incorporated, the circuit being adapted to execute or to be used in the execution of the communication method, in accordance with the invention, or of the selection process, in accordance with the invention.

According to another aspect, the invention also relates to a transmission system comprising:
- at least a first vehicle, a second vehicle and a third device, the second vehicle being able to communicate peer-to-peer with the first vehicle and to communicate with the third device; and
- a controller according to the invention, configured to control a data transmission mode used by the first vehicle to communicate with the second vehicle and with the third device.

The controller can be embedded for example in a base station or in a centralized management entity of a wireless communications network.

In addition, the third device can be either:
- A third vehicle or any other equipment able to communicate peer-to-peer with the first vehicle; Where
- A base station of a cellular communications network to which the first vehicle is connected; Where
- the second vehicle.

The transmission system benefits from the same advantages mentioned above as the control method and the controller according to the invention.

It is also possible, in other embodiments, for the control method, the controller and the transmission system according to the invention to have all or part of the aforementioned characteristics in combination.

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 which is devoid of any limiting character. In the figures:
FIG. 1, already described, represents a cellular network in which a vehicle V20 sends data to a vehicle V30 via a vehicle V10;
FIG. 2 represents, in its environment, a transmission system according to the invention in a first embodiment;
FIG. 3 schematically illustrates the hardware architecture of a controller according to the invention;
FIG. 4 represents, in the form of a flowchart, the main steps implemented by the controller of FIG. 3 to determine the mode of data transmission applied by a vehicle of the transmission system of FIG. 2, in a particular embodiment ;
FIG. 5 represents, in its environment, a transmission system according to the invention in a second embodiment;
FIG. 6 represents, in its environment, a transmission system according to the invention in a third embodiment.
Description of embodiments

FIG. 2 represents, in its environment, a transmission system 1 according to the invention, in a first embodiment in which the third device is a vehicle.

In this first embodiment, the transmission system 1 thus comprises three vehicles, V1, V2 and V3, able to communicate with each other peer-to-peer, in other words to establish wireless connections between them via an appropriate communication interface and to exchange data directly via these wireless connections without going through a central server. The vehicles V1, V2 and V3 thus form a mesh network (or “mesh” network) also called an ad hoc network.

No limitation is attached to the nature of the communication interfaces used by the vehicles of the transmission system 1 to ensure their connectivity. This may be for example a wireless network 4 ^th or 5 ^th Generation (4G or 5G ie).

No limitation is attached either to the nature of the vehicles V1, V2 and V3. These can be either land vehicles (e.g. cars, trains), airborne vehicles (e.g. drones, etc.), etc., these vehicles being likely to be in motion.

In accordance with the invention, the transmission system 1 further comprises a controller CTRL in accordance with the invention, able to communicate with the vehicles V1, V2 and V3 via one or more communication interfaces (eg 4G or 5G).

It is assumed here that each of the vehicles V1, V2 and V3 is equipped with an interference elimination module, implementing for example a successive or parallel interference elimination algorithm and/or an interference elimination algorithm. self-interference for vehicles required to operate in full-duplex mode. Such a module is known to those skilled in the art and is not further described here.

Furthermore, we consider here, by way of illustration, a transmission of data D2 from the vehicle V2 to the vehicle V1 via a peer-to-peer link on a given radio resource such as for example a frequency f0 or a predetermined frequency band, and a transmission of data D1 from the vehicle V1 to the vehicle V3 via a peer-to-peer link on this same radio resource. It is noted that the peer-to-peer links between the vehicles V1 and V2 on the one hand, and V1 and V3 on the other hand can be based on the same communication interface or on different communication interfaces.

In the example considered, the data D1 includes the data D2 transmitted by the vehicle V2, and may possibly include additional data added by the vehicle V1. In other words, the volume, denoted VOL1, of the data D1 is greater than or equal to the volume, denoted VOL2, of the data D2.

It is also assumed here that the various vehicles are configured by default to adopt during their peer-to-peer communications a half-duplex data transmission mode, the latter limiting the interference generated during these communications. However, this assumption is not limiting in itself.

According to the invention, in such a situation, the controller CTRL controls the mode of transmission used by the vehicle V1 which is involved at a given instant in two peer-to-peer communications with the vehicle V2 and the vehicle V3 respectively. More precisely, it is for the controller CTRL to select for the vehicle V1 a data transmission mode from among:
- a half-duplex data transmission mode in which the vehicle V1 can only communicate, that is to say send or receive data, with a single vehicle at a given time using the same radio resource (in the species here the frequency f0). In half-duplex mode, the vehicle V1 cannot transmit and receive data simultaneously on the same resource; and
- A full-duplex data transmission mode in which the vehicle V1 can simultaneously transmit data to a vehicle and receive data from a vehicle using the same radio resource.

To this end, the control method according to the invention is implemented within the CTRL controller by means of software and/or hardware components defining various duly configured functional modules (determination, activation modules, etc.).

More particularly, in the embodiment described here, the controller CTRL is integrated into a centralized management entity of the transmission system 1 and has the hardware architecture of a computer, as illustrated schematically in FIG . It notably comprises a processor 2, a random access memory 3, a read only memory 4, a non-volatile flash memory 5 as well as communication means 6 enabling it to communicate with the various vehicles V1, V2 and V3. No limitation is attached to the nature of the communication interface(s) implemented by the means 6 for this purpose (4G, 5G, WiFi communication interface, etc.).

The read only memory 4 of the controller CTRL here constitutes a recording medium in accordance with the invention, readable by the processor 2 and on which is recorded a computer program Prog in accordance with the invention, comprising instructions for the execution of the steps of a control method according to the invention.

In other words, the computer program Prog defines the various functional modules of the controller CTRL enabling it to implement the control method according to the invention, namely, in the embodiment described here (cf. figure 2):
- a determination module 7, configured to determine whether a COND condition (detailed in more detail later) is verified; and
- an activation module 8, configured to activate if necessary (that is to say if the COND condition is verified) a full-duplex transmission mode at the level of the vehicle V1 to communicate with the vehicle V2 and with the V3 vehicle.

In accordance with the invention, the COND condition is chosen from two conditions C1 and C2 according to the transmission rates accessible in full-duplex mode between the vehicles V1, V2 and V3. More specifically:

- if, when the vehicle V1 is configured in full-duplex mode, the data transmission rate D2, denoted R _FD (D2), between the vehicle V2 and the vehicle V1 is lower (or equal here) to the transmission rate of the data D1, denoted R _FD (D1), between the vehicle V1 and the vehicle V3, the condition COND that the controller CTRL tests is a condition C1 defined by:

µ _FD,1,1 < µ ₀ /[exp(1/(B+C)-1]-1

with µ ₀ = P ₂ ⁽¹⁾ /(I _oth +N _th ), B=1/log(1+ µ _HD,1,2 )) and C=W2/[W1.log(1+µ _{HD,3 ,1} ))]

or :

μ _HD,1,2 is the SINR received at the level of the vehicle V1 when the latter, in half-duplex mode, receives a volume VOL2 of data (corresponding to the data D2) from the vehicle D2;

μ _HD,3,1 is the SINR received at the level of the vehicle V3 when the vehicle V1, in half-duplex mode, transmits a volume VOL1 of data (corresponding to the data D1) to the vehicle V3;

P ₂ ⁽¹⁾ designates the power of the data D2 received by the vehicle V1 and transmitted by the vehicle V2;

W1 and W2 respectively designate passbands of the transmission channels between the vehicle V1 and the vehicle V3, and between the vehicle V2 and the vehicle V1;

I _oth is an interference level generated at the level of the vehicle V1 by at least a fourth communication device (for example another vehicle) transmitting data on a radio resource (eg frequency f0) on which simultaneously, the vehicle V1, in full-duplex mode, transmits the volume VOL1 of data to the vehicle V3 and receives the volume VOL2 of data from the vehicle V2 or on which simultaneously the vehicle V1, in half-duplex mode, receives the volume VOL2 of data from the vehicle V2; and

N _th is a noise level received by the vehicle V1;

- otherwise, if the transmission rate R _FD (D2) is greater than the transmission rate R _FD (D1), the condition COND is a condition C2 defined by:

_µFD,3,1 > exp(1/A)-1

with A=αB+(W1/W2)C, α=VOL2/VOL1, and µ _FD,3,1 is the SINR received at the level of the vehicle V3 when the vehicle V1, in full-duplex mode, transmits the volume VOL1 of data to the vehicle V3 on a radio resource (eg frequency f0) and simultaneously receives the volume VOL2 of data from the vehicle V2 on the same radio resource.

To derive the conditions C1 and C2 which are considered alternately in accordance with the invention to trigger at the level of the vehicle V1 the full-duplex data transmission mode, the inventors were interested in the hypotheses leading to a transmission time T _FD (D2 ,D1) data D2 from vehicle V2 to vehicle V1 and data D1 from vehicle V1 to vehicle V3 in full-duplex mode less than the corresponding transmission time T _HD (D2,D1) in half-duplex mode.

When the vehicle V1 is configured in full-duplex transmission mode, the data D1 and D2 being able to be transmitted and received simultaneously by the vehicle V1 on the same radio resource (frequency f0 here), it follows that the transmission time T _FD ( D2,D1) is equal to:
T _FD (D2,D1)=VOL2/(min(R _FD (D2),R _FD (D1))+(VOL1-VOL2)/R _FD (D1)
It is assumed here that as soon as the vehicle V1 begins to receive data (called “first data”) from the vehicle V2, it is able to transmit them to the vehicle V3 and the time required for these first data to reach the vehicle is neglected. V1. Furthermore, as mentioned above, the vehicles V1 and V3 are assumed here configured in half-duplex mode.

When the vehicle V1 is configured in half-duplex mode, since the data D1 and D2 cannot be sent and received simultaneously by the vehicle V1 on the same radio resource (frequency f0 here), the result is that the transmission time T _HD ( D2,D1) is equal to:
T _HD (D2,D1)= T _HD (D2)+ T _HD (D1)=VOL2/R _HD (D2)+VOL1/R _HD (D1)
or :
- T _HD (D2) and T _HD (D1) designate respectively the transmission times when the vehicle V1 operates in half-duplex mode of the data D2 from the vehicle V2 to the vehicle V1 and of the data D1 from the vehicle V1 to the vehicle V3; and
- R _HD (D2) and R _HD (D1) designate respectively the bit rate of the link between the vehicle V2 and the vehicle V1 and the bit rate of the link between the vehicle V1 and the vehicle V3 when the vehicle V1 operates in half-mode duplex.

The inventors have therefore judiciously determined two conditions C1 and C2 making it possible to obtain the following inequality (1):
VOL2/(min(R _FD (D2),R _FD (D1))+(VOL1-VOL2)/R _FD (D1)<VOL2/R _HD (D2)+VOL1/R _HD (D1)

In order not to sacrifice the transmission performance of data D1 and D2 in full-duplex mode, the inventors have cleverly converted this inequality into terms of SINR by using Shannon's relation giving the capacity of a transmission channel as a function of the SINR of the channel. In a manner known per se, the capacity of a channel designates the upper limit denoted here Rmax of the data rate which can be transmitted reliably on this channel, that is to say with an error probability which tends towards zero, depending on the SINR. More particularly, the inventors have used here the following relationship:
Rmax=Wlog(1+SINR)
where W denotes the bandwidth of the considered channel. It should be noted that the log can be either a logarithm in base 2, 10, or a natural logarithm depending on the unit considered for Rmax (eg logarithm in base 2 for a capacity expressed in bit/s).

The inventors used this upper limit given by Shannon to express the flow rates R_FD(D2),R_FD(D1) R_HD(D2) and R_HD(D1) involved in inequality (1). More specifically, they considered the following hypotheses:
- the transmission rate R_FD(D2) was approximated by:
R_FD(D2)=W2.log(1+µ_FD,1,2)
where µ_FD,1,2designates, as indicated previously, the SINR ratio received at the level of the vehicle V1 when the vehicle V1, in full-duplex mode, receives the data D2 coming from the vehicle V2 on the frequency f0 and simultaneously transmits on this same frequency the data D1 towards the V3 vehicle. The SINR µ_FD,1,2can be written in the following form, with the notations introduced previously:
µ_FD,1,2=P₂ ⁽¹⁾/(I_1.1+I_oh+N_th)
In this expression, P₂ ⁽¹⁾ designates the power of the data D2 received by the vehicle V1 and transmitted by the vehicle V2, and I_1.1is the level of self-interference reached at the level of the vehicle V1 when the latter operates in full-duplex mode, in other words the level of self-interference generated by the vehicle V1 itself. This level of self-interference corresponds to the level of residual interference after the vehicle V1 has eliminated the interference tainting the data D2 transmitted by the vehicle V2. It is described for example in the document by T. Huusari et al. entitled "Wideband Self-Adaptive RF Cancellation Circuit for Full-Duplex Radio: Operating Principle and Measurements", IEEE Vehicular Technology Conference, March 2015, and can be expressed as the product of a so-called self-interference factor β of the vehicle V1 by the transmission power P₁used by the vehicle V1 to send the data D1 to the vehicle V3 (i.e. I_1.1= β.P₁);
- the transmission rate R_FD(D1) was approximated by:
R_FD(D1)=W1.log(1+µ_FD,3.1)
where µ_FD,3.1designates, as indicated previously, the SINR report received at the level of the vehicle V3 when the vehicle V1, in full-duplex mode, transmits the data D1 to the vehicle V3 on the frequency f0 and simultaneously receives on this same frequency data D2 coming from the vehicle V2. The SINR µ_FD,3.1can be written in the following form, with the notations introduced previously:
µ_FD,3.1=P₁ ⁽³⁾ /(I_3.2+I_oh+N_th)
where P₁ ⁽³⁾designates the power of the data D1 received by the vehicle V3 and transmitted by the vehicle V1, and I_3.2designates the interference generated by the vehicle V2 at the level of the vehicle V3 when it transmits the data D2 on the frequency f0 simultaneously with the transmission of the data D1 to the vehicle V3 by the vehicle V1;
- the transmission rate R_HD(D1) was approximated by:
R_HD(D1)=W1.log(1+µ_HD,3.1)
where µ_HD,3.1is, as indicated previously, the SINR ratio received by the vehicle V3 when the vehicle V1, in half-duplex mode, transmits the data D1 to the vehicle V3. The SINR µ_HD,3.1can be written in the following form, with the notations introduced previously:
µ_HD,3.1=P₁ ⁽³⁾/(I_oh+N_th)
- the transmission rate R_HD(D2) was approximated by:
R_HD(D2)=W2.log(1+µ_HD,1,2)

where μ _HD,1,2 is, as indicated previously, the SINR ratio received at the level of the vehicle V1 when the vehicle V1, in half-duplex mode, receives the data D2 from the vehicle V2. The SINR µ _HD,1,2 can be written in the following form:
µ _HD,1,2 = P ₂ ⁽¹⁾ /(I _oth +N _th ).

As mentioned previously, condition C1 corresponds to the case where:
R _FD (D2)<R _FD (D1)

The inequality (1) can then be written in the form:
VOL2/R _FD (D2)+(VOL1-VOL2)/R _FD (D1) < VOL2/R _HD (D2)+VOL1/R _HD (D1)

However, it follows from the above relations that R _FD (D1)<R _HD (D1). Therefore, the inequality (1) can be written:
VOL2/R _FD (D2)< VOL2/R _HD (D2)+VOL2/R _HD (D1)
that is :
1/R _FD (D2)< 1/R _HD (D2)+1/R _HD (D1)

By transferring to this inequality the expressions for R _FD (D2), R _HD (D2), R _HD (D1) provided previously, we obtain the following inequality:
1/log(1+µ _FD,1,2 ) < 1/log(1+µ _HD,1,2 )+W2/[W1.log(1+µ _HD,3,1 )]

By asking :
B=1/log(1+ µ _HD,1,2 )) and C=W2/[W1.log(1+µ _HD,3,1 ))
(B and C being positive quantities), the above inequality can be written:
0<1/log(1+µ _FD,1,2 ) <B+C

However, as indicated previously, µ _FD,1,2 = P _2,1 /(β.P ₁ +I _oth +N _th ) which can also be written in the form:
µ _FD,1,2 =µ ₀ /(1+µ _FD,1,1 )
with µ ₀ =P ₂ ⁽¹⁾ /(I _oth +N _th ) and µ _FD,1,1 = β.P ₁ /(I _oth +N _th ).

It follows that the inequality (1) is verified in the case where R _FD (D2)<R _FD (D1) if the following condition C1 is verified:
µ _FD,1,1 < µ ₀ /[exp(1/(B+C)-1]-1

As mentioned before, condition C2 corresponds to R _FD (D1)<R _FD (D2).

Inequality (1) then becomes:
VOL1/R _FD (D1) < VOL2/R _HD (D2)+VOL1/R _HD (D1)

By transferring to this inequality the expressions of R _FD (D1), R _HD (D2), R _HD (D1) provided previously, we obtain the following inequality:
1/log(1+µ _FD,3,1 ) < (VOL2.W1)/[VOL1.W2.log(1+µ _HD,1,2 )]+1/log(1+µ _HD,3,1 )

It follows from this inequality, by posing α=VOL2/VOL1, the following condition (C2):
_µFD,1,3 > exp(1/A)-1
with A=αB+(W1/W2)C, B and C having been introduced previously during the derivation of condition C1.

It is noted that the quantities (SINR, powers, interferences, etc.) present in the conditions C1 and C2 can vary with time, and in particular with the speed of the vehicles V1, V2 and V3. For the sake of simplification of the notations, we omit in the formulas described here the indexing with respect to time.

We will now describe how these conditions C1 and C2 are considered by the controller CTRL, in a particular embodiment. FIG. 4 represents the main steps of the control method implemented by the controller CTRL, in this particular embodiment, to decide which mode of data transmission must use the vehicle V1 to receive data from the vehicle V2 and transmit data to vehicle V3 (or vice versa).

It is assumed that the vehicles V1, V2 and V3 have previously paired up two by two (i.e. V1 with V2 and V1 with V3 in the example considered here) in order to be able to establish peer-to-peer communication. No limitation is attached to the wireless communication interface used by the vehicles V1, V2 and V3 to establish this communication: it may be for example a communication interface based on a transmission system of OFDMA type (for Orthogonal Frequency-Division Multiple Access) such as an LTE (Long Term Evolution) communication interface.

Such pairing between the vehicles V1, V2 and V3 can be performed for example as described in the document by J.M.Kelif et al. titled “Meeting Energy-Efficient and QoS Requirements of 5G using D2D communications”, December 18, 2017 (https://arxiv.org/abs/1712.06461).

It is assumed that initially the vehicles V1, V2 and V3 are configured to communicate with each other in half-duplex mode.

Following this pairing, the vehicle V1, respectively the vehicle V3, performs various measurements, in a manner known per se, by exploiting for example predefined pilot signals emitted by the vehicle V2, respectively by the vehicle V1.

The vehicle V1 notably measures the power P ₂ ⁽¹⁾ received from the vehicle V2, but also the power received from other "interfering" communication devices simultaneously using the same radio resource as the vehicle V2 (namely here, the same frequency f0) to communicate with the vehicle V1. It may for example be other vehicles communicating peer-to-peer and using the frequency f0 simultaneously with the vehicles V1 and V2. This power constitutes the overall interference I _oth undergone by the vehicle V1 in half-duplex transmission mode. It is noted that it is the same interference I _oth which affects the vehicle V1 when the latter communicates in full-duplex mode (to which is then combined the self-interference I _1,1 generated by the vehicle V1 itself) .

It is noted that the measurements carried out by the vehicle V1 can be implemented at various times, for example periodically or on detection of particular events, so as to evaluate continuously or quasi-continuously the conditions in which the vehicle is located. vehicle V1 and be able to reassess at various times the relevance of switching it or not to a full duplex transmission mode.

The vehicle V1 also estimates the level of self-interference I _1.1 that it generates when it operates in full-duplex transmission mode. As indicated previously, this level of self-interference corresponds to the level of residual interference after the vehicle V1 has eliminated the interference marring the data transmitted by the vehicle V2. It is described for example in the document by T. Huusari et al. entitled "Wideband Self-Adaptive RF Cancellation Circuit for Full-Duplex Radio: Operating Principle and Measurements", IEEE Vehicular Technology Conference, March 2015. This level of self-interference I _1.1 can be expressed equivalently in the form of the product of a so-called self-interference factor β of the vehicle V1 and the transmission power P ₁ used by the vehicle V1 to transmit data to the base station BS, _{i.e. I 1.1} = β.P ₁ . This self-interference factor β is a fixed parameter, which can be evaluated by or for the vehicle V1 beforehand.

Similarly, the vehicle V3 notably measures the power P ₁ ⁽³⁾ received from the vehicle V1, but also the power received from other "interfering" communication devices simultaneously using the same radio resource as the vehicle V1 (at know here, the same frequency f0) to communicate with the vehicle V1. These may for example be other vehicles communicating peer-to-peer and using the frequency f0 simultaneously with the vehicles V1 and V3, such as for example the vehicle V2 when the vehicle V1 communicates in full-duplex mode. The power measured from the vehicle V2 constitutes the interference I _3.2 generated by the vehicle V2 at the level of the vehicle V3 when the vehicle V1 operates in full-duplex transmission mode, and receives data from the vehicle V2 on the frequency f0 even as it transmits data to the vehicle V3 on this same frequency.

It is noted that the measurements carried out by the vehicle V3 can be implemented at various times, for example periodically or on detection of particular events, so as to evaluate continuously or quasi-continuously the conditions in which the vehicle is located. vehicle V1 and be able to reassess at various times the relevance of switching it or not to a full duplex transmission mode.

The various measurements and estimates made by the vehicles V1 and V3 are transmitted by the latter to the controller CTRL (step E10). It is noted that the vehicle V1 can transmit either to the controller CTRL an estimate of its self-interference level I _1.1 or the individual parameters β and P ₁ .

In the embodiment described here, from the measurements and estimates received from the vehicles V1 and V3, the controller CTRL, via its determination module 7, first of all determines which link V1-V2 or V1-V3 has the best rate when the vehicle V1 operates in full-duplex, in other words, what is the highest rate between R_FD(D1) and R_FD(D2) (test step E20). To this end, the determination module 7 can use the formulas introduced previously to estimate the flow rates R_FD(D1) and R_FD(D2), based on measurements and estimates received from vehicles V1 and V3 (P₂ ⁽¹⁾, I_1.1,I_oh+N_threceived from vehicle V1, P₁ ⁽³⁾and I_3.2received from vehicle V3). It is assumed here that he also knows the bandwidths W1 and W2 as well as the volumes VOL1 and VOL2; this information could be provided to it for example by the vehicles V1, V2 and V3.

If the controller CTRL determines that R _FD (D1) is less than R _FD (D2) (answer yes to test step E20), then the controller CTRL, via its determination module 7, then determines whether the condition C2 described above is verified (test step E30), i.e. if:
_µFD,1,3 > exp(1/A)-1
with A=αB+(W1/W2)C, α=VOL2/VOL1, and
B=1/log(1+ µ _HD,1,2 )) and C=W2/[W1.log(1+µ _HD,3,1 ))

The ratios μ _HD,1,2 and μ _HD,3,1 are evaluated from the formulas provided previously by reporting in these formulas the measurements/estimates received from the vehicles V1 and V3.

If the determination module 7 determines that the condition C2 is satisfied (answer yes to the test step E30), the activation module 8 of the controller CTRL activates the full-duplex transmission mode at the level of the vehicle V1 (step E40) . To this end, it sends a message to the vehicle V1, via its means of communication 6. Following this activation, the vehicle V1 can communicate simultaneously with the vehicles V2 and V3 using the same radio resource: it can in particular receive the data D2 of the vehicle V2 at the same time and on the same radio resource (same frequency f0 for example) that it transmits its data D1 to the vehicle V3.

If the condition C2 is not verified (answer no to step E30), the controller CTRL does not modify the configuration of the vehicle V1 and lets it use the half-duplex mode to communicate with the vehicles V2 and V3, and in particular receive the data D2 from the vehicle D2 and transmit the data D1 to the vehicle V3 (step E50).

If the controller determines during step E20 that R _FD (D1) is greater than R _FD (D2) (answer no to test step E20), then the controller CTRL, via its determination module 7, then determines whether the condition C1 described above is verified (test step E60), i.e. if:
µ _FD,1,1 < µ ₀ /[exp(1/(B+C)-1]-1
with µ ₀ =P ₂ ⁽¹⁾ /(I _oth +N _th ) and µ _FD,1,1 = β.P ₁ /(I _oth +N _th ).

The ratios µ ₀ and µ _FD,1,1 are evaluated from the measurements/estimates received from the vehicles V1 and V3.

If the determination module 7 determines that the condition C1 is satisfied (answer yes to the test step E60), the activation module 8 of the controller CTRL activates the full-duplex transmission mode at the level of the vehicle V1 (step E40) , as indicated previously.

If the condition C1 is not verified (response no to step E60), the controller CTRL does not modify the configuration of the vehicle V1 and lets it use the half-duplex mode to receive the data D2 from the vehicle D2 and transmit the data D1 to vehicle V3 (step E50).

Note that if the controller CTRL determines that R _FD (D1)=R _FD (D2), it can use either of the conditions C1 and C2 to determine whether the full-duplex module must be activated. In the first embodiment described here, it uses condition C1.

Steps E10 to E60 are preferably repeated at various times to determine whether a change in configuration of vehicle V1 should be considered. Note that to estimate the different quantities involved in the conditions C1 and C2, the controller CTRL can either use measurements reported at different times by the vehicles V1 and V3, or deduce from the measurements reported at a time t0 the value of some of these quantities at any instant t taking into account the speed of movement of the vehicle V1. For example, the SINR µ _HD,3,1 at a time t can be evaluated from the SINR µ _HD,3,1 evaluated at a time t0, the relative speed ν ₁₃ of the vehicle V1 with respect to the vehicle V3 and from the distance DIST _1.3 between the vehicles V1 and V3 using the following relationship:
µ _HD,3,1 (t)= µ _HD,3,1 (t0)+(t-t0).ν ₁₃ .[dµ _HD,3,1 (t)/dDIST1,3]

The relative speed and the distance can be deduced by the controller from speeds and/or geographical positions reported by the vehicles V1 and V3 (which we then assume for example equipped with GPS (Global Positioning System) receivers).

In the embodiment illustrated in FIG. 2, the CTRL controller is integrated into a centralized management entity of the transmission system 1. Such an entity is for example a server communicating with the various vehicles V1, V2 and V3 (and possibly d other vehicles for a peer-to-peer network including other vehicles). In a variant embodiment, the controller can be integrated into one of the vehicles and in particular into the vehicle V1.

In the embodiment illustrated in FIG. 2, the configuration of the vehicle V1 is considered for receiving data D2 from a vehicle V2 and transmitting data D1 to a vehicle V3 (third communication device within the meaning of the invention), distinct from the vehicle V2, using the same radio resource (frequency f0 in the example considered). The conditions C1 and C2 derived above can also be considered in other contexts.

They can in particular be envisaged, in a simplified form, when the vehicle V3 and the vehicle V2 are one and the same vehicle, as illustrated in a second embodiment in FIG . Note that in this second embodiment, if the vehicle V1 is configured by the controller CTRL to operate in full-duplex mode, this also implies operation of the vehicle V2 in full-duplex mode.

We will demonstrate below that conditions C1 and C2 also apply in this second embodiment. Indeed, in this second embodiment:
- the transmission rate R_FD(D2) can be approximated by:
R_FD(D2)=W2.log(1+µ_FD,1,2)
where µ_FD,1,2designates the SINR ratio received at the level of the vehicle V1 when the vehicle V1, in full-duplex mode, receives the data D2 coming from the vehicle V2 on the frequency f0 and simultaneously transmits the data D1 on this same frequency to the vehicle V2. The SINR µ_FD,1,2can be written in the following form, with the notations introduced previously:
µ_FD,1,2=P₂ ⁽¹⁾/(I_1.1+I₁+N_th)
Yes₁designates the interference generated at the level of the vehicle V1 by the communication devices other than the vehicles V1 and V2 which simultaneously use the same radio resource as V1 and V2 (same frequency f0 here);
- the transmission rate R_FD(D1) can be approximated by:
R_FD(D1)=W1.log(1+µ_FD,2,1)
where µ_FD,2,1designates the SINR ratio received at the level of the vehicle V2 when the vehicle V1, in full-duplex mode, transmits the data D1 to the vehicle V2 on the frequency f0 and simultaneously receives on this same frequency data D2 coming from the vehicle V2. The SINR µ_FD,2,1can be written in the following form, with the notations introduced previously:
µ_FD,2,1=P₁ ⁽²⁾ /(I_2.2+I₂+N_th)
Yes_2.2denotes the self-interference generated by the vehicle V2 (which can be expressed as previously described for the vehicle V1 in the first embodiment as the product of the transmission power P₂of the vehicle V2 by a self-interference factor) and I₂designates the interference generated at the level of the vehicle V2 by the communication devices other than the vehicles V1 and V2 which simultaneously use the same radio resource as V1 and V2 (same frequency f0 here);
- the transmission rate R_HD(D1) can be approximated by:
R_HD(D1)=W1.log(1+µ_HD,2.1)
where µ_HD,2.1is the SINR ratio received by vehicle V2 when vehicle V1, in half-duplex mode, transmits data D1 to vehicle V2. The SINR µ_HD,2.1can be written in the following form, with the notations introduced previously:
µ_HD,2.1=P₁ ⁽²⁾/(I₂+N_th)
- the transmission rate R_HD(D2) was approximated by:
R_HD(D2)=W2.log(1+µ_HD,1,2)

where μ _HD,1,2 is the SINR ratio received at vehicle V1 when vehicle V1, in half-duplex mode, receives data D2 from vehicle V2. The SINR µ _HD,1,2 can be written in the following form:
µ _HD,1,2 = P ₂ ⁽¹⁾ /(I ₁ +N _th ).

As mentioned previously, condition C1 corresponds to the case where:
R _FD (D2)<R _FD (D1)

The inequality (1) can then be written in the form:
VOL2/R _FD (D2)+(VOL1-VOL2)/R _FD (D1) < VOL2/R _HD (D2)+VOL1/R _HD (D1)

However, it follows from the above relations that R _FD (D1)<R _HD (D1). Therefore, the inequality (1) can be written:
1/R _FD (D2)< 1/R _HD (D2)+1/R _HD (D1)

By transferring in this inequality, the expressions of R _FD (D2), R _HD (D2), R _HD (D1) provided previously, we obtain the following inequality:
1/log(1+µ _FD,1,2 ) < 1/log(1+µ _HD,1,2 )+W2/[W1.log(1+µ _HD,2,1 )]

By asking :
B=1/log(1+ µ _HD,1,2 )) and C=W2/[W1.log(1+µ _HD,2,1 ))
0<1/log(1+µ _FD,1,2 ) <B+C

However, as indicated previously, µ _FD,1,2 = P ₂ ⁽¹⁾ /(I _1,1 +I ₁ +N _th ) which can also be written in the form:
µ _FD,1,2 =µ ₀ /(1+µ _FD,1,1 )
with µ ₀ =P ₂ ⁽¹⁾ /(I ₁ +N _th ) and µ _FD,1,1 = β.P ₁ /(I ₁ +N _th ).

It follows that the inequality (1) is verified in the case where R _FD (D2)<R _FD (D1) if the following condition C1 is verified:
µ _FD,1,1 < µ ₀ /[exp(1/(B+C)-1]-1

It is noted that the expressions of B and C correspond to those introduced in the first embodiment by replacing the index 3 by the index 2, the third vehicle and the second vehicle being one and the same vehicle (ie V3=V2) .

Furthermore, it is noted that in the second embodiment where the third communication device is the vehicle V2, this condition C1 can be simplified to facilitate, when certain hypotheses are satisfied, the verification carried out by the determination module 7 of the controller CTRL during step E60.

Indeed, in the second embodiment, the bandwidths W1 and W2 can be assumed to be identical. In addition, if the vehicles V1 and V2 are in the same environment and they use the same transmission powers, it can reasonably be considered that they are subject to the same interference and that, as a result, the SINR µ _{HD,2 ,1} and µ _HD,1,2 are (substantially) identical. It follows that B and C are (substantially) equal.

Condition C1 can then be simplified to:
µ _FD,1,1 < µ ₀ /[(1+µ ₀ ) ^1/2 -1]-1

In other words, if the following hypotheses are satisfied, the determination module 7 can, during the determination step E60 if the condition C1 is satisfied, determine if the simplified condition above is verified. This constitutes a step for determining whether condition C1 is satisfied within the meaning of the invention.

As mentioned previously, the condition C2 corresponds to the case where RFD(D1)<RFD(D2).

Inequality (1) then becomes:
VOL1/R _FD (D1) < VOL2/R _HD (D2)+VOL1/R _HD (D1)

By transferring to this inequality the expressions of R _FD (D1), R _HD (D2), R _HD (D1) when V2=V3, we obtain the following inequality:
1/log(1+µ _FD,2,1 ) < (VOL2.W1)/[VOL1.W2.log(1+µ _HD,1,2 )]+1/log(1+µ _HD,2,1 )

It follows from this inequality, with α=VOL2/VOL1, the condition C2:
_µFD,1,2 > exp(1/A)-1
with A=αB+(W1/W2)C= αB+C (like W1=W2) and B and C such that:
B=1/log(1+ µ _HD,1,2 )) and C=W2/[W1.log(1+µ _HD,2,1 ))

Furthermore, it is noted that like the condition C1, this condition C2 can be simplified to facilitate, when certain hypotheses are satisfied, the verification performed by the determination module 7 of the controller CTRL during the step E30.

Indeed, in the second embodiment, if the vehicles V1 and V2 are in the same environment and they use the same transmission powers, it can reasonably be considered that they are subject to the same interference and that for this reason , the SINR µ _HD,2,1 and µ _HD,1,2 are (substantially) identical. It follows that B and C are (substantially) equal.

Condition C2 can then be simplified to:
µ _FD,1,1 < µ ₀ /[(1+µ ₀ ) ⁿ -1]-1
with n=VOL1/(VOL1+VOL2).

The invention also applies advantageously when the third device is not a vehicle, but a base station BS or an access point of a wireless telecommunications network (for example a 4G or 5G cellular network, but no limitation is attached to the nature of this network) to which the vehicle V1 is connected, as illustrated in a third embodiment in FIG .

In this third embodiment, the configuration of the vehicle V1 is considered to receive data D2 from a vehicle V2 and transmit data D1 to the base station BS using the same radio resource (frequency f0 in the example considered) . The assumption is also made that at a given instant, the base station BS cannot receive data on a radio resource (and in particular on the frequency f0 used by the vehicles V1 and V2 to communicate peer-to-peer) only one user device connected to the base station (namely the vehicle V1 or another user device denoted U).

The inventors have demonstrated that the same conditions C1 and C2 can be derived in this third embodiment (by replacing the index 3 by BS in these conditions).

Indeed, when R _FD (D2)<R _FD (D1), the inequality (1) can be written in the form:
VOL2/R _FD (D2)+(VOL1-VOL2)/R _FD (D1) < VOL2/R _HD (D2)+VOL1/R _HD (D1)

In the case where the third device is a base station BS, the inventors have considered the following approximations (by considering the notations previously introduced):
- the transmission rate R _FD (D2) is approximated by:
R _FD (D2)=W2.log(1+µ _FD,1,2 )
where µ _FD,1,2 designates the SINR ratio received at the level of the vehicle V1 when the vehicle V1, in full-duplex mode, receives the data D2 coming from the vehicle V2 on the frequency f0 and simultaneously transmits on this same frequency the data D1 to base station BS. The SINR µ _FD,1,2 can be written in the form:
µ _FD,1,2 = P ₂ ⁽¹⁾ /(I _1,1 +I _oth +N _th )

In this expression, P₂ ⁽¹⁾ designates the power of the data D2 received by the vehicle V1, I_1.1is the level of self-interference reached at the level of the vehicle V1 when the latter operates in full-duplex mode, in other words generated by the vehicle V1 itself (i.e. I_1.1= β.P₁), I_ohis the level of interference generated at the level of the vehicle V1 by devices other than the vehicles V1, V2 and the user equipment U transmitting data on a radio resource (in this case on the frequency f0) on which simultaneously , the vehicle V1, in full-duplex mode, transmits the data D1 to the base station BS and receives the data D2 from the vehicle V2 or on which simultaneously the vehicle V1, in half-duplex mode, receives the data D2 from the vehicle V2 , and N_this a noise level received by the vehicle V1 (in full-duplex mode or in half-duplex mode). It can easily be shown that:

µ _FD,1,2 =µ ₀ /(1+µ _FD,1,1 )

with the notations µ₀and µ_FD,1,1previously introduced;
- the transmission rate R_FD(D1) is approximated by:
R_FD(D1)=W1.log(1+µ_FD,BS,1)
where µ_FD,BS,1designates the SINR report received at the base station BS when the vehicle V1, in full-duplex mode, transmits the data D1 to the base station BS on the frequency f0 and simultaneously receives on this same frequency data D2 coming from of the vehicle V2. The SINR µ_FD,BS,1can be written in the form, with the notations introduced previously:
µ_FD,BS,1=P₁ ^(BS) /(I_BS.2+I_oh+N_th)
Yes_BS.2denotes the level of interference generated by the vehicle V2 at the level of the base station BS;
- the transmission rate R_HD(D1) is approximated by:
R_HD(D1)=W1.log(1+µ_HD,BS,1)
where µ_HD,BS,1is, as indicated previously, the SINR report received by the base station BS when the vehicle V1, in half-duplex mode, transmits the data D1 to the base station BS. The SINR µ_HD,BS,1can be written in the form, with the notations introduced previously:
µ_HD,BS,1=P₁ ^(BS)/(I_oh+N_th)
- the transmission rate R_HD(D2) is approximated by:
R_HD(D2)=W2.log(1+µ_HD,1,2)

where μ _HD,1,2 is the SINR ratio received at vehicle V1 when vehicle V1, in half-duplex mode, receives data D2 from vehicle V2. To express the SINR µ _HD,1,2 while taking into account the interference likely to be generated by the various communication devices simultaneously using the frequency f0, the inventors considered that according to a realistic hypothesis, commonly implemented, the station base station BS can only, at a given instant and on a given radio resource (typically on the frequency f0), receive data from at most one user equipment connected to the base station BS. The vehicle V1 operating in half-duplex mode and receiving the data D2 on the frequency f0, it therefore does not transmit simultaneously to the base station BS. Another user equipment connected to the base station BS (namely the user equipment U here) is therefore capable of simultaneously transmitting data (the data D) to the base station BS on the frequency f0 when the vehicle V2 transmits the data D2 to the vehicle V1. This user equipment U generates via the transmission of its data D to the base station BS an interference denoted I _1,U on the data D2 received by the vehicle V1. In view of these remarks, the SINR µ _HD,1,2 can then be written in the form:
µ _HD,1,2 = P ₂ ⁽¹⁾ /(I _1,U +I _oth +N _th )
By setting µ _HD,1,U = I _1,U /(I _1,U +I _oth +N _th ), we can show that:
µ _HD,1,2 = µ ₀ (1-µ _HD,1,U )

It follows from the relationships given above that R _FD (D1)< R _HD (D1). This consideration applied to inequality (1) leads to the following inequality:
VOL2/R _FD (D2)< VOL2/R _HD (D2)+VOL2/R _HD (D1)
which can also be written in the form:
1/log(1+µ ₀ /(1+µ _FD,1,1 )) < 1/log(1+µ ₀ (1-µ _HD,1,U ))+W2/[W1.log(1+ µ _HD,BS,1 ))]

By asking :
B=1/log(1+ µ ₀ (1- µ _HD,1,U ))
and
C= W2/[W1.log(1+µ _HD,BS,1 ))]
the previous inequality is written:

1/log(1+µ ₀ /(1+µ _FD,1,1 ))<B+C

which leads to condition C1:

µ _FD,1,1 < µ ₀ /[exp(1/(B+C))-1]-1

When the rate R_FD(D1) is less than the rate R_FD(D2), inequality (1) becomes:
VOL2/R_FD(D1)+(VOL1-VOL2)/R_FD(D1) < VOL2/R_HD(D2)+VOL1/R_HD(D1)
that is
VOL1/R_FD(D1)< VOL2/R_HD(D2)+VOL1/R_HD(D1)
which can still be written by transferring the expressions of R_FD(D1),R_HD(D2) and R_HD(D1):
1/log(1+µ_FD,BS,1) < α/log(1+µ_HD,1,2)+1/log(1+µ_HD,BS,1)
with α=(VOL2/VOL1).(W1/W2). It is noted that α=1 in the case of privileged application where the data D1 correspond to the data D2 (and therefore VOL2=VOL1) and W1=W2.

As indicated previously, the SINR µ _FD,BS,1 can be approximated by:
µ _FD,BS,1 =P ₁ ^(BS) /(I _oth +N _th +I ₂ , _BS )

By asking :
A= α/log(1+µ_HD,1,2)+1/log(1+µ_HD,BS,1)
we obtain the condition:
1/log(1+µ_FD,BS,1) <A
equivalent to condition C2:
µ_FD,BS,1>exp(1/A)-1

The information necessary for the evaluation of the condition C2 can be obtained, in this third embodiment, by the controller CTRL, of the vehicle V1 as described above, and of the base station BS which can measure the power levels and d interference received from pilot signals transmitted by the vehicle V1 and/or by the vehicle V2.

As mentioned previously, to estimate the different quantities involved in the conditions C1 and C2, the controller CTRL can either use measurements uploaded at different times by the vehicle V1 and by the base station BS, or deduce measurements uploaded at a time t0 the value of some of these quantities at any instant t taking into account the speed of movement of the vehicle V1. This is the case for example of the SINR µ _HD,1,U which can be estimated at a time t as follows:
µ _HD,1,U (t)= µ _HD,1,U (t0)+(t-t0).ν _1. [dµ _HD,1,U (t)/dDIST _1,U ]

where ν ₁ designates the speed of the vehicle V1 (or relative speed of the vehicle V1 with respect to the user equipment U if the latter is mobile) and DIST _1,U the distance separating the user equipment U from the vehicle V1. The speed and the distance can be fed back to the controller by the vehicle V1 or by the base station. Thus, in the second embodiment illustrated in FIG. 5 and in the third embodiment illustrated in FIG. 6, the controller can implement the same steps E10 to E60 previously described in the first embodiment and illustrated in figure 4 to determine which configuration to apply to the vehicle V1 and in particular if the latter can be configured to use a full-duplex transmission mode in its communications with the vehicle V2 (second embodiment), or in its communications with the vehicle V2 and with the base station BS (third embodiment). Only the estimate of the ratios involved in conditions C1 and C2 may change. This estimate is made on the basis of the relationships provided above for the various embodiments envisaged.

The invention thus advantageously makes it possible to benefit from the advantages of the full-duplex transmission mode to allow a vehicle V2 to transmit data to a third device via another vehicle V1 without sacrificing the quality of the transmissions, whether this third device or another vehicle, another user equipment or a base station of a network to which the vehicle V1 is connected. It also makes it possible to benefit from the advantages of full duplex mode during peer-to-peer communications between two vehicles V1 and V2. It has a privileged but non-limiting application in the context of 4G networks and 5G networks which offer the possibility to very varied user equipment, such as vehicles, to be connected and to benefit from high speeds.

Claims (11)

Method of controlling, by a controller (CTRL), a data transmission mode intended to be used by a first vehicle (V1) to communicate with a second vehicle (V2) and with a third device (V3, BS, V2 ), said method comprising:
- a step of determining (E30, E60) whether a condition is verified, said condition being:
● if, when the first vehicle is in full-duplex mode, a data transmission rate between the first vehicle and the second vehicle is less than or equal to a data transmission rate between the first vehicle and the third device, a condition C1 such that:
µ _FD,1,1 < µ ₀ /[exp(1/(B+C)-1]-1
with µ ₀ = P ₂ ⁽¹⁾ /(I _oth +N _th ), B=1/log(1+ µ _HD,1,2 ))
and C=W2/[W1.log(1+µ _HD,3,1 ))] where:
μ _HD,1,2 is a signal-to-interference-plus-noise ratio (SINR) received at the level of the first vehicle when the first vehicle, in half-duplex mode, receives a volume VOL2 of data from the second vehicle;
μ _HD,3,1 is a SINR received at the level of the third communication device when the first vehicle, in half-duplex mode, transmits a volume VOL1 of data to the third device;
P ₂ ⁽¹⁾ designates the power of the volume VOL2 of data received by the first vehicle and transmitted by the second vehicle;
W1 and W2 respectively designate passbands of the transmission channels between the first vehicle and the third device, and between the second vehicle and the first vehicle;
I _oth is an interference level generated at the level of the first vehicle by at least a fourth device transmitting data on a radio resource on which simultaneously, the first vehicle, in full-duplex mode, transmits the volume VOL1 of data to the third device and receives the volume VOL2 of data from the second vehicle or on which simultaneously the first vehicle, in half-duplex mode, receives the volume VOL2 of data from the second vehicle; and
N _th is a noise level received by the first vehicle;
● otherwise a condition C2 such that:
_µFD,3,1 > exp(1/A)-1
with A=αB+(W1/W2)C and α=VOL2/VOL1 and where µ _FD,3,1 is the SINR received at the level of the third device when the first vehicle, in full-duplex mode, transmits the volume VOL1 of data to the third device on a radio resource and simultaneously receives on this resource the volume VOL2 of data from the second vehicle;
- if said condition is verified, a step of activating (E50) a full-duplex data transmission mode at the level of the first vehicle to communicate with the second vehicle and with the third device. Control method according to claim 1, in which the third device is:
- A base station (BS) of a wireless network to which the first vehicle is connected; Where
- a vehicle (V3, V2) or other equipment able to communicate peer-to-peer with the first vehicle. Control method according to claim 2, in which the third device is the second vehicle. Control method according to any one of Claims 1 to 3, in which the controller (CTRL) is integrated into a centralized management entity of a wireless telecommunications network. Control method according to any one of Claims 1 to 4, in which the determination step is reproduced at different instants. Computer program (Prog) comprising instructions for the execution of a control method according to any one of claims 1 to 5, when said program is executed by a computer. Computer-readable storage medium on which a computer program (Prog) according to Claim 6 is recorded. Controller (CTRL) configured to control a data transmission mode used by a first vehicle to communicate with a second vehicle (V2) and with a third device (V3, BS, V2), this controller comprising:
- a determination module, configured to determine whether a condition is verified, said condition being:
● if when the first vehicle is in full-duplex mode, a data transmission rate between the first vehicle and the second vehicle is less than or equal to a data transmission rate between the first vehicle and the third device, a condition C1 such as :
µ _FD,1,1 < µ ₀ /[exp(1/(B+C)-1]-1
with µ ₀ = P ₂ ⁽¹⁾ /(I _oth +N _th ), B=1/log(1+ µ _HD,1,2 ))
and C=W2/[W1.log(1+µ _HD,3,1 ))] where:
μ _HD,1,2 is a signal-to-interference-plus-noise ratio (SINR) received at the level of the first vehicle when the first vehicle, in half-duplex mode, receives a volume VOL2 of data from the second vehicle;
μ _HD,3,1 is a SINR received at the level of the third device when the first vehicle, in half-duplex mode, transmits a volume VOL1 of data to the third device;
P ₂ ⁽¹⁾ designates the power of the volume VOL2 of data received by the first vehicle and transmitted by the second vehicle;
W1 and W2 respectively designate passbands of the transmission channels between the first vehicle and the third device, and between the second vehicle and the first vehicle;
I _oth is an interference level generated at the level of the first vehicle by at least a fourth device transmitting data on a radio resource on which simultaneously, the first vehicle, in full-duplex mode, transmits the volume VOL1 of data to the third device and receives the volume VOL2 of data from the second vehicle or on which simultaneously the first vehicle, in half-duplex mode, receives the volume VOL2 of data from the second vehicle; and
N _th is a noise level received by the first vehicle;
● otherwise a condition C2 such that:
_µFD,3,1 > exp(1/A)-1
with A=αB+(W1/W2)C and α=VOL2/VOL1 and where µ _FD,3,1 is the SINR received at the level of the third communication device when the first vehicle, in full-duplex mode, transmits the volume VOL1 of data to the third device on a radio resource and simultaneously receives on this resource the volume VOL2 of data from the second vehicle;
- an activation module configured to activate if said condition is verified, a full-duplex data transmission mode at the first vehicle to communicate with the second vehicle and with the third device. Transmission system (1) comprising:
- at least a first vehicle (V1), a second vehicle (V2) and a third device (V3, BS, V2), the second vehicle being able to communicate peer-to-peer with the first vehicle and to communicate with the third device ; and
- a controller (CTRL) according to claim 8, configured to control a data transmission mode used by the first vehicle to communicate with the second vehicle and with the third device. Transmission system (1) according to claim 9 wherein the controller is embedded in a centralized management entity of a wireless communications network. A transmission system (1) according to claim 9 or 10 wherein the third device is:

• a vehicle or other equipment able to communicate peer-to-peer with the first vehicle; Where
• a base station of a cellular communications network to which the first vehicle is connected.