FR3120716A1 - method and device for transmitting an access authorization to a vehicle - Google Patents

Abstract

The invention relates to a method for transmitting an access authorization to a vehicle, which transmission is carried out from a mobile user terminal (EQU) to on-board computer equipment (EQV) in said vehicle, which authorization is in the form of an OFDM digital signal, said primary signal (SP), the method comprising the following steps carried out in said mobile terminal: generation of a secondary signal (SS) defined by an inverse logarithmic function which decreases when the amplitude (x) of the primary signal (SP) increases, digital filtering of the secondary signal (SS) so as to obtain a filtered secondary signal (SS_FILT), addition of the filtered secondary signal (SS_FILT) to empty subcarriers of the primary signal (SP) in such a way obtaining an envelope signal (SE), amplifying the envelope signal (SE) to obtain an amplified signal (SA), transmitting the amplified signal (SA) to the on-board computer equipment (EQV), theq ual transmission is carried out through a short-range wireless link (LCP). Figure to be published with abstract = figure 2

Description

method and device for transmitting an access authorization to a vehicle

Technical area.

The invention relates to a method and a device for transmitting an access authorization to a vehicle.

The field of the invention relates in particular to the wireless transmission of signals between user equipment and equipment on board vehicles, and more particularly the transmission of signals making it possible to control said vehicles (in particular their opening and/or their taking control) .

State of the art.

Solutions are known for reserving and activating the opening of the vehicle by means of user equipment. The document US2015/0137943 describes for example such a solution.

Current systems generally work the same way: a smart phone of the user, of the Smartphone type, connects to a centralized server. This includes a database in which the last known positions of available vehicles are recorded. By querying this database, the Smartphone user can select an available vehicle and reserve it. This reservation information is transmitted to the server, via a data network, for example a 4G or 5G network. Still through the network, the server transmits the reservation information to computer equipment on board the vehicle. The user moves near the vehicle and requests access authorization from the server. This can transmit the access authorization to the Smartphone. The Smartphone and the on-board equipment can then exchange access authorization by means of a short-range Bluetooth type wireless link.

However, there is a problem when the vehicle is parked in a place not covered by a data network. Neither the smartphone nor the vehicle's on-board equipment can exchange data with the server. This can happen in underground car parks or in enclosed garages.

The access authorization communicated between the Smartphone and the computer equipment on board the vehicle is in the form of a digital signal which is advantageously an OFDM signal.

OFDM (for Orthogonal Frequency Division Multiplexing) is a transmission method consisting in distributing the digital signal (the access authorization) that one wishes to transmit over a large number of sub-carriers. The signals of the different subcarriers can overlap, but, thanks to the orthogonality, they do not interfere with each other.

One of the main disadvantages of OFDM to date remains that OFDM signals have a wide band and consequently have a large variation in amplitude. The envelope of the signal thus modulated then has a strong dynamic. Furthermore, the signal thus modulated, before being transmitted, must be amplified in the Smartphone to compensate for the propagation attenuations. The peak to average power ratio (PAPR) of the transmitted signal is thus generally very high and increases with the number of subcarriers.

A high value of the PAPR leads to taking a step back from the compression point of the power amplifier (of the order of the PAPR) to avoid non-linear distortions. This results in a spectral rise in the level of the secondary lobes (ACPR, for "Adjacent Channel Power Ratio"), the generation of harmonics, the creation of interference between non-linear symbols, the creation of interference between carriers, which causes in particular transmission errors and degradation of the bit error rate (BER). This is particularly problematic in the case where the transmitted signal is a vehicle access authorization.

These distortions also result in a reduction in the energy efficiency of the power amplifier (a few% instead of, conventionally, 70%) and therefore a significant increase in the consumption of the transmitter integrated in the Smartphone. This is an important constraint for the Smartphone insofar as the consumption of the power amplifier can represent more than 50% of the total consumption of the Smartphone.

One objective of the invention is to overcome this state of affairs.

Presentation of the invention.

The solution proposed by the invention is a method for transmitting an access authorization to a vehicle, which transmission is carried out from a mobile user terminal to computer equipment on board said vehicle, which authorization is in the form of an OFDM digital signal, called primary signal, the method comprising the following steps carried out in said mobile terminal:
- a) generation of a secondary signal defined by an inverse logarithmic function which decreases when the amplitude of the primary signal increases,
- b) digital filtering of the secondary signal so as to obtain a filtered secondary signal,
- c) addition of the filtered secondary signal to empty sub-carriers of the primary signal so as to obtain an enveloped signal,
- d) amplification of the enveloped signal to obtain an amplified signal,
- e) transmission of the amplified signal to the on-board computer equipment in said vehicle, which transmission is carried out through a short-range wireless link.

Thus, the invention proposes a reduction clipping of the PAPR, by means of a secondary signal defined by an inverse logarithmic function. This secondary signal has decreasing power as the amplitude of the source signal increases. Thus, the power added to the primary signal, to obtain the enveloped signal, is low.

According to the invention, the secondary signal, defined by an inverse logarithm function, is added, after filtration, to the empty sub-carriers of the primary signal, which makes it possible to reduce the PAPR, while avoiding the introduction of noise on the sub-carriers. data carriers of said primary signal. It should be noted that the number of sub-carriers of the primary signal is not increased.

Furthermore, the invention does not lead to any degradation of the BER (Binary Error Rate). Indeed, the addition of the secondary signal to the empty subcarriers of the primary signal makes it possible to obtain a signal with a compact envelope, with limited noise. The noise generated is in fact limited to only the sub-carriers of the enveloped signal corresponding to the empty sub-carriers of the primary signal.

In the context of the invention, this method makes it possible to reduce the errors in transmitting the access authorization to the vehicle, while optimizing the consumption of the transmitter integrated in the user's Smartphone.

Other advantageous features of the invention are listed below. Each of these characteristics can be considered alone or in combination with the remarkable characteristics defined above, and be the subject, where applicable, of one or more divisional patent applications.

According to one embodiment, in step c) the filtered secondary signal is added to empty subcarriers of the primary signal.

• k représente un paramètre de contrôle de la puissance moyenne de sortie, tel que k>1,
• x représente l’amplitude du signal primaire (SP).

According to one embodiment, the inverse logarithmic function is defined by the following equation: Where :

• k represents an average output power control parameter, such that k>1,
• x represents the amplitude of the primary signal (SP).

According to one embodiment, in step b), a filtering means selects sub-carriers of the secondary signal which correspond to empty sub-carriers of the primary signal.

According to one embodiment, steps a), b) and c) are iterated until a variation in the peak power to average power ratio (PAPR) of less than 0.1 dB is obtained.

Another aspect of the invention relates to a device for transmitting an access authorization to a vehicle, which authorization is in the form of an OFDM digital signal, called the primary signal, the device comprising:
- a generator of a secondary signal defined by an inverse logarithmic function which decreases when the amplitude of the primary signal increases,
- a digital filter adapted to filter the secondary signal so as to obtain a filtered secondary signal,
- a means for adding the filtered secondary signal to empty sub-carriers of the primary signal so as to obtain an envelope signal,
- an envelope signal amplifier to obtain an amplified signal,
- a transmitter suitable for transmitting the amplified signal to on-board computer equipment in a vehicle, through a short-range wireless link.
. Brief description of figures.

Other advantages and characteristics of the invention will appear better on reading the description of a preferred embodiment which will follow, with reference to the appended drawings, produced by way of indicative and non-limiting examples and in which:
diagrams the arrangement of different elements of user equipment and on-board computer equipment in a vehicle.
illustrates steps of a method according to the invention,
illustrates a secondary signal defined by an inverse logarithmic function which decreases as the amplitude of the primary signal increases,
is an embodiment of a device for implementing the method.

Description of embodiments.

The method that is the subject of the invention generates manipulations of physical elements, in particular signals (electrical or magnetic) and digital data, capable of being stored, transferred, combined, compared, etc., and making it possible to achieve a result wish.

The invention implements one or more computer applications executed by computer equipment, terminals or servers. For the sake of clarity, it should be understood within the meaning of the invention that " an equipment, terminal or server does something " means " the computer application executed by a processing unit of the equipment, terminal or server does something thing ”. Just as “ the computer application does something ” means “ the computer application executed by the processing unit of the equipment, terminal or server does something ”.

Again for the sake of clarity, the present invention may refer to one or more " logical computer processes ". These correspond to the actions or results obtained by the execution of instructions from different computer applications. Also, it must also be understood within the meaning of the invention that “ a logical computer process is adapted to do something ” means “ the instructions of a computer application executed by a processing unit do something ”.

Again for the sake of clarity, the following clarifications are made to certain terms used in the description and the claims:
- " Computer resource " can be understood in a non-limiting way as: component, hardware, software, file, connection to a computer network, amount of RAM memory, hard disk space, bandwidth, processor speed, number of CPUs, etc. .
- " Computer server " can be understood in a non-limiting way as: computer device (hardware or software) comprising computer resources to perform the functions of a server and which offers services, computer, plurality of computers, virtual server on the internet , virtual server on cloud, virtual server on a platform, virtual server on local infrastructure, server networks, cluster, node, server farm, node farm, etc.
- " Request " means an execution order that can follow a communication protocol and includes input parameters (question, information, etc.) and possibly return parameters (response, information, etc.), which may be in a related format to the protocol used.
- " Processing unit " can be understood in a non-limiting way as: processor, microprocessors, CPU (for Central Processing Unit), etc.
- " Computer application " can be understood as: software, computer program, computer firmware, lines of executable code, software, etc.
- " Data network " can be understood in a non-limiting way as: internet network, cellular network, satellite network, etc. It is a set of computer equipment linked together to exchange, securely or not, information and/or data according to a communication protocol (ISDN, Ethernet, ATM, IP, CLNP, TCP, HTTP, etc.) .
- " Service " can be understood in a non-limiting manner as all the functionalities offered and provided by a server and/or by at least one piece of computer equipment. The service may include, for example, the following functionalities: reservation of a vehicle, location of a vehicle, locking/unlocking of a vehicle, etc. The service includes in particular the activation of access to a vehicle.
- " Vehicle " can be understood in a non-limiting manner as a rental vehicle or a self-service vehicle (in English "car sharing") made available to "customers" or members. The vehicle can be: an autonomous car (capable of driving on the road, without the intervention of a driver), a car or a truck (thermal and/or electric engine), a motorized two-wheeler (thermal and/or electric engine) , a bicycle (classic or with electric assistance), a scooter (classic or with electric assistance), a skateboard, an electric unicycle, a Segway, a boat, etc.

By referring to the , the vehicle incorporates EQV on-board computer equipment. This equipment can for example be part of a telematics unit allowing the vehicle to exchange information (e.g. geographical position, speed, etc.) with a remote server presented in the introductory part of this description, through a network of data. The EQV computer equipment can also be dedicated equipment, independent of the telematics unit.

The on-board equipment EQ _V comprises, among other computer resources, a processing unit 10, a signal transmitter/receiver 11 and one or more memories 12 in which a computer application is recorded. These different elements are connected at least to the processing unit 10 by a communication bus.

The transmitter/receiver 11 is suitable for exchanging signals, via a short-range wireless link L _CP with the user equipment EQ _U described later in the description. The link L _CP has for example a range less than or equal to 100 meters, or even less than or equal to 20 meters. The signals exchanged are preferably radiofrequency signals. The L _CP links preferably use a communication protocol of the following family: Bluetooth, Wifi, Z-Wave, ANT, ZIGBEE.

The user (natural person) has a mobile terminal EQ _U which comprises a communication interface, for example GSM, 3G, 4G, 5G or Wifi, to establish a wireless communication link with the remote server presented above, at the through a data network. The mobile terminal EQ _U is preferably an intelligent telephone (Smartphone), a digital tablet, a laptop computer, etc.

The mobile terminal EQ _U incorporates a processing unit 20, a signal transmitter/receiver 21 and one or more memories 22 in which a computer application for implementing the service (“application-service”) is recorded. These different elements are connected at least to the processing unit 20 by a communication bus. It also includes the computing resources making it possible to carry out the steps of the method of the invention. The transmitter/receiver 21 is similar to that of the on-board equipment EQ _V.

When the user moves near the vehicle and requests an access authorization from the server, the latter transmits the access authorization to the mobile terminal EQ _U . The mobile terminal EQ _U and the on-board equipment EQ _V will then exchange access authorization by means of the short-range wireless link L _CP .

According to one embodiment, the access authorization is in the form of an OFDM signal, called a primary signal. The invention is based on the addition of a secondary signal to this primary signal.

This secondary signal has an amplitude that decreases logarithmically as the amplitude of the primary signal increases. The power added to the primary signal, to obtain an enveloped signal, is thus low.

On the , the method for transmitting the primary signal SP, comprises the following steps carried out in the mobile terminal EQU:
- generation Gen_SS of a secondary signal SS defined by an inverse logarithmic function which decreases when the amplitude of the primary signal SP increases,
- digital filtering FILT of the secondary signal SS so as to obtain a filtered secondary signal SS_FILT,
- addition AJ of the filtered secondary signal SS_FILT to empty sub-carriers of the primary signal SS so as to obtain a signal with envelope SE,
- AMP amplification of the enveloped signal SE to obtain an amplified signal SA,
- TRANS transmission of the amplified signal SA to the on-board computer equipment EQ _V , through the short-range wireless link L _CP .

The illustrates the secondary signal SS defined by an inverse logarithmic function (clipping function) defined by the following equation: where :
- k represents an average output power control parameter, such that k>1,
- x represents the amplitude of the primary signal SP.

The secondary signal SS decreases when the amplitude x of the primary signal SP increases.

By referring to the , the mobile terminal EQU comprises means for generating the secondary signal GEN SS defined by the logarithmic function according to [Math 1]. In an OFDM context, the secondary signal SS can be formed by OFDM symbols.

The secondary signal SS is then digitally filtered by a filter means FILT. According to one embodiment, this filtering means FILT implements digital filtering reserved in the frequency band allocated to transmission in OFDM modulation. The filtering means FILT selects the subcarriers of the secondary signal SS which correspond to the empty subcarriers of the primary signal SP.

In the context of an OFDM modulation conforming to the IEEE 802.15 standard, a plurality of sub-carriers are used, including: data sub-carriers used to carry the primary signal; - Pilot sub-carriers for carrying a synchronization pilot signal; - and empty sub-carriers carrying no data from the primary signal.

The "useful band" is the frequency band comprising the data sub-carriers and the pilot sub-carriers which are actually used for the transmission of the primary signal. The empty sub-carriers are located outside the useful band and form “guard bands”. The useful band and the guard bands form the frequency band allocated to a transmission in OFDM modulation.

The filtered secondary signal SS_FILT is thus added to the empty subcarriers of the guard bands of the primary signal SP, which makes it possible to reduce the PAPR, while avoiding introducing noise to the data subcarriers of said primary signal.

The steps of generation GEN of the secondary signal SP, of filtering FILT and of adding AJT are preferentially iterated until a variation of the PAPR of less than 0.1 dB is obtained.

When the filtered secondary signal SS_FILT is added to the primary signal SP, an enveloped signal SE is obtained. This signal is amplified using a power amplifier AMP to obtain an amplified signal SA which will be transmitted by the transmitter 21.

The arrangement of the various elements and/or means and/or steps of the invention, in the embodiments described above, should not be understood as requiring such an arrangement in all implementations. Other variations may be provided.

Further, one or more features disclosed only in one embodiment may be combined with one or more other features disclosed only in another embodiment. Similarly, one or more features disclosed only in one embodiment may be generalized to other embodiments, even if such feature or features are described only in combination with other features.

Claims (6)

Method for transmitting an access authorization to a vehicle, which transmission is carried out from a mobile user terminal (EQ_U) to on-board computer equipment (EQ_V) in said vehicle, which authorization is in the form of an OFDM digital signal, called primary signal (SP), the method comprising the following steps carried out in said mobile terminal:

1. generation of a secondary signal (SS) defined by an inverse logarithmic function which decreases when the amplitude (x) of the primary signal (SP) increases,
2. digital filtering of the secondary signal (SS) so as to obtain a filtered secondary signal (SS_FILT),
3. addition of the filtered secondary signal (SS_FILT) to empty sub-carriers of the primary signal (SP) so as to obtain an enveloped signal (SE),
4. amplification of the enveloped signal (SE) to obtain an amplified signal (SA),
5. transmission of the amplified signal (SA) to the on-board computer equipment (EQ _V ), which transmission is carried out through a short-range wireless link (L _CP ).

Method according to claim 1, wherein in step c) the filtered secondary signal is added on empty subcarriers of the primary signal. Method according to one of the preceding claims, in which the inverse logarithmic function is defined by the following equation:

where :

• k represents an average output power control parameter, such that k>1,
• x represents the amplitude of the primary signal (SP).

Method according to one of the preceding claims, in which in step b), a filtering means (FILT) selects subcarriers of the secondary signal (SS) which correspond to empty subcarriers of the primary signal (SP) . Method according to one of the preceding claims, in which steps a), b) and c) are iterated until a variation in the ratio of peak power to average power (PAPR) of less than 0.1 dB is obtained. . Device for transmitting an access authorization to a vehicle, which authorization is in the form of an OFDM digital signal, called primary signal (SP), the device comprising:

• a generator (GEN) of a secondary signal (SS) defined by an inverse logarithmic function which decreases when the amplitude (x) of the primary signal (SP) increases,
• a digital filter (FILT) adapted to filter the secondary signal (SS) so as to obtain a filtered secondary signal (SS_FILT),
• means for adding the filtered secondary signal (SS_FILT) to empty subcarriers of the primary signal (SP) so as to obtain an enveloped signal (SE),
• an amplifier (AMP) of the envelope signal (SE) to obtain an amplified signal (SA),
• a transmitter (21) adapted to transmit the amplified signal (SA) to on-board computer equipment (EQ _V ) in a vehicle, through a short-range wireless link (L _CP ).