Method for characterizing the quality of a radio link between a vehicle and a ground unit

Abstract

The invention relates to a method for characterizing the quality of a radio link between a vehicle and a ground unit, the method comprising: - measuring a parameter of interest of a radio link between a vehicle (3) and a ground unit (40) as a function of time or as a function of a coordinate of the vehicle (3) along a predefined route, the parameter of interest being representative of the quality of the radio link; - measuring the coordinate as a function of time; - calculating a reading of the parameter of interest as a function of the coordinate on the basis of the measurements of the parameter of interest and of the coordinate; - calculating a reference curve of the parameter of interest of a reference radio link between the vehicle (3) and the ground unit (40) as a function of the coordinate; and - characterizing the quality of the radio link by comparing the reading with the reference curve.

Description

[0001] TITLE: Method for characterizing the quality of a radio link between a vehicle and ground equipment

[0002] The present invention relates to a method for characterizing the quality of a radio link between a vehicle, in particular a railway vehicle, moving along a predefined route and at least one piece of ground equipment.

[0003] While moving along its route, a railway vehicle must be in constant radio communication with ground-based servers or IT equipment via radio equipment on the ground and on the train. This radio communication, if carried out for signalling purposes, enables the vehicle to regularly transmit to the ground-based servers / IT equipment information representative of its position along the route and to regularly receive in return authorizations to progress along the route from the ground-based servers / IT equipment. The authorizations to progress are generated by the ground-based servers / IT equipment and depend at least in part on the coordinate of the vehicle along the route.

[0004] When the vehicle does not receive permission to proceed within a certain period of time, the vehicle stops moving along the route by applying a so-called emergency braking procedure. Such an emergency braking procedure disrupts traffic and in certain rare cases (long immobilization) can pose a risk to the vehicle and its occupants.

[0005] The lack of progress authorization may result from a deliberate failure to generate authorization from ground servers / IT equipment, for example when the vehicle's position along the route requires a stop in vehicle movement, or from a degradation of radio links between the vehicle and ground equipment, making it impossible to transfer information representative of the vehicle's position and / or progress authorizations.

[0006] Such degradations of radio communication can occur when the radio equipment on the vehicle and / or on the ground has design or adjustment problems (change of orientation of the antennas), when it deteriorates, when the radio environment is disturbed for example by the appearance of new obstacles or when interference phenomena occur.

[0007] Detecting or anticipating degradations of radio links between the vehicle and ground equipment is significantly complex because they are generally not due to malfunctions or obvious phenomena. Currently, it is common practice, firstly, to detect severe degradations of radio links, these severe degradations leading in particular to unwanted emergency braking procedures, then, secondly, to carry out specific radio measurement campaigns aimed at precisely detecting the degradations and diagnosing them.

[0008] These radio measurement campaigns are then carried out outside of service hours during designated slots, using tools specifically designed for these tasks.

[0009] However, the monitoring and diagnosis of damage is then carried out under conditions which are not very representative of the actual driving conditions of the vehicle and are based on specific measurements specifically carried out with the aim of detecting and identifying damage which is already suspected.

[0010] One of the aims of the invention is to overcome these drawbacks by proposing a method for monitoring the integrity of the radio links between the vehicle and the ground equipment in an efficient and precise manner.

[0011] To this end, the invention relates to a method for characterizing the quality of a radio link between a vehicle, in particular a railway vehicle, moving along a predefined route and at least one piece of ground equipment, the position of the vehicle along the predefined route being characterized at each instant by a coordinate along this predefined route, the vehicle and the at least one piece of ground equipment exchanging radio signals via the radio link, the method comprising the following steps:

[0012] - measurement of a parameter of interest of the radio link between the vehicle and the at least one piece of ground equipment as a function of time or as a function of the coordinate of the vehicle, the parameter of interest being representative of the quality of the radio link between the vehicle and the at least one piece of ground equipment;

[0013] - measurement of the vehicle coordinate as a function of time;

[0014] - calculation of a reading of the parameter of interest as a function of the vehicle coordinate from the measurement of the parameter of interest and the measurement of the coordinate;

[0015] - calculation of a reference curve of the parameter of interest of a reference radio link between the vehicle and the at least one piece of ground equipment as a function of the coordinate of the vehicle; and

[0016] - characterization of the quality of the radio link between the vehicle and at least one piece of ground equipment by comparing the reading of the parameter of interest with the reference curve of the parameter of interest. The invention thus makes it possible to characterize the quality of the radio link between the vehicle and a piece of ground equipment directly using measurements of one or more parameters of interest and coordinates relating to said vehicle.

[0017] The characterization of the quality of the radio link is therefore based on an analysis of the radio link actually connecting the vehicle and the ground equipment.

[0018] According to optional characteristics of the characterization process, taken in isolation or in any technically feasible combination:

[0019] - the vehicle is connected with one of the ground equipments via a useful radio link to communicate with a ground station, the measurement of the parameter of interest being carried out to be taken into account to determine the ground equipment with which the vehicle is connected via the useful radio link;

[0020] - the measurement of the vehicle coordinate is carried out by the vehicle to receive an authorization for the vehicle to progress on the predefined route issued by the ground station;

[0021] - the characterization of the quality of the radio link between the vehicle and the at least one piece of ground equipment comprises the calculation of at least one radio link quality indicator, the at least one quality indicator being a variable having a value representative of a satisfactory quality of the radio link or a value representative of a degraded quality of the radio link;

[0022] - when the value of the at least one quality indicator is representative of a degraded quality of the radio link, the characterization of the quality of the radio link further comprises a determination of a cause of the degradation of the radio link;

[0023] - determining the cause of the degradation of the radio link involves a comparison of the reading of the parameter of interest with typical curves of the parameter of interest corresponding to different causes of degradation;

[0024] - when the value of the at least one quality indicator is representative of satisfactory quality but tends over time towards a value representative of degraded quality, the characterization of the quality of the radio link further comprises a determination of a duration at the end of which the value of the quality indicator will be representative of degraded quality;

[0025] - the calculation of a first quality indicator includes a comparison of a decomposition of the reading of the parameter of interest into components calculated by principal component analysis and a decomposition of the reference curve of the parameter of interest into components calculated by principal component analysis;

[0026] - the at least one piece of ground equipment comprises a first radio transmission-reception unit and a second radio transmission-reception unit, the radio link comprising a first channel connecting the first radio transmission-reception unit and the vehicle and a second channel connecting the second radio transmission-reception unit and the vehicle, the calculation of the first quality indicator comprising a comparison of the reading of the parameter of interest corresponding to the first channel of the radio link with the reading of the parameter of interest corresponding to the second channel of the radio link;

[0027] - the calculation of at least one second quality indicator is a function of the time taken to make a cellular transfer, packet losses, measured flow rates, latencies and / or vehicle speed;

[0028] - the characterization of the quality of the radio link between the vehicle and at least one piece of ground equipment also includes taking into account additional analysis data;

[0029] - when the method comprises a step of measuring the parameter of interest of the radio link between the vehicle and the at least one piece of ground equipment as a function of time, the calculation of the reading of the parameter of interest comprises the synchronization of the function representing the values ​​of the parameter of interest measured as a function of time and the function representing the values ​​of the coordinate of the vehicle as a function of time by associating the longest plateau, or respectively a plurality of consecutive plateaus of the function representing the values ​​of the coordinate of the vehicle as a function of time with the longest portion, or respectively a plurality of portions, of the function representing the values ​​of the parameter of interest measured as a function of time for which, or respectively which, the variance of the value of the parameter of interest is minimal; and

[0030] - when the method comprises a step of measuring the parameter of interest of the radio link between the vehicle and the at least one piece of ground equipment as a function of time, the calculation of the reading of the parameter of interest comprises the association of the parameter of interest at a given instant with the coordinate of the vehicle at the given instant by interpolation in the time domain of the function representing the values ​​of the parameter of interest measured as a function of time and the function representing the values ​​of the coordinate of the vehicle measured as a function of time; and

[0031] - when the method comprises a step of measuring the parameter of interest of the radio link between the vehicle and the at least one piece of ground equipment as a function of the coordinate of the vehicle, the calculation of the reading of the parameter of interest comprises the association of the parameter of interest with a given coordinate with an instant corresponding to the coordinate of the vehicle by interpolation in the spatial domain of the function representing the values ​​of the parameter of interest measured as a function of the coordinate and of the function representing the values ​​of the coordinate of the vehicle measured as a function of time. Other aspects and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example and with reference to the appended drawings, in which:

[0032] [Fig 1] Figure 1 is a schematic representation illustrating an assembly comprising a vehicle, two ground radio equipments and a ground station, the assembly being suitable for carrying out the method of characterizing the radio link between the vehicle and at least one ground radio equipment according to the invention;

[0033] [Fig 2] Figure 2 is a detailed schematic representation illustrating the whole of Figure 1;

[0034] [Fig 3] Figure 3 is a graph having the parameter of interest as its ordinate and the coordinate of the vehicle as its abscissa, on which are superimposed a reading of the parameter of interest of the radio link between the vehicle and ground equipment as a function of the coordinate of the vehicle, resulting from a first pass of the vehicle near the ground equipment, a reading of the parameter of interest of the radio link between the vehicle and the ground equipment as a function of the coordinate of the vehicle, resulting from a second pass of the vehicle near the ground equipment and a reference curve of the parameter of interest of a reference radio link between the vehicle and the ground equipment as a function of the coordinate of the vehicle;

[0035] [Fig 4] Figure 4 is a schematic representation of a flowchart representing the process of characterizing the quality of the radio link.

[0036] Referring to Figures 1 and 2, an assembly 1 comprises a vehicle 3 configured to move along a predefined route, at least one ground equipment 40 arranged along the predefined route and a ground station 50.

[0037] Vehicle 3 is, for example, a guided land vehicle, in particular a rail vehicle. In this case, the predefined route is defined along a railway track (not shown).

[0038] The position of vehicle 3 on the route is characterized at each instant by a coordinate P along this route.

[0039] As will be detailed below, the vehicle 3 is configured to communicate with the ground station 50 via at least one piece of ground equipment 40.

[0040] According to the example described in the present application, the set 1 comprises a plurality of ground equipment 40 distributed along the predefined route. Each ground equipment 40 is connected to the ground station 50.

[0041] The vehicle 3 is capable of being connected with at least one piece of ground equipment 40 by a radio link. In particular, the vehicle 3 is capable of exchanging radio signals with the ground equipment 40 with which it is connected via the radio link. In the following, a single piece of ground equipment 40 is described. It will be understood that each piece of ground equipment 40 has the same structure and the same functions.

[0042] The ground equipment 40 is typically a base station in the case of a mobile network or an access point in the case of a Wi-Fi network.

[0043] The ground equipment 40 notably comprises at least one radio transmission-reception unit 42.

[0044] The radio transceiver unit 42 comprises a transceiver 43 and at least one physical radiocommunication antenna 44 connected to the transceiver 43. The physical antenna 44 comprises, for example, several radiating elements constituting a MIMO (“Multiple-Input Multiple Output” in English, “multiple inputs, multiple outputs” in French).

[0045] As will be detailed below, for the sake of redundancy, the ground equipment 40 preferably comprises at least two radio transceiver units 42, in particular exactly two radio transceiver units 42. This is an example of a redundant configuration; there may be other configurations allowing redundancy, for example through redundant radio coverage by deploying twice as many ground equipment 40.

[0046] For example, for the sake of complete redundancy, the ground equipment 40 is grouped in pairs, the ground equipment 40 of the same pair being located substantially at the same location along the route. In particular, the ground equipment 40 of the same pair provides substantially identical radio coverage. In other words, in a nominal operating case, the radio links between the vehicle 3 and each of the ground equipment 40 of the same pair are substantially identical.

[0047] The vehicle 3 is configured to communicate permanently with the ground station 50 via at least one piece of ground equipment 40 among the plurality of pieces of ground equipment 40. The vehicle 3 is in particular configured to be connected with said at least one piece of ground equipment 40 via a radio link useful for communicating with the ground station 50.

[0048] Advantageously, the vehicle 3 is also configured to be connected with at least one other piece of ground equipment 40 among the plurality of ground equipment 40, in particular via a secondary radio link.

[0049] When a ground equipment 40 comprises two radio transceiver units 42, the radio link between the vehicle 3 and said ground equipment 40 comprises a first channel connecting a first radio transceiver unit 42 of said ground equipment 40 and the vehicle 3 and a second channel connecting a second radio transceiver unit 42 of said ground equipment 40 and the vehicle 3. In this case, the radio equipment of the vehicle 3 is able to switch to the second channel in the event of loss of connection on the first channel.

[0050] Advantageously, the vehicle 3 is configured to communicate with the ground station 50 to transmit its coordinate P to the ground station 50 and to receive in return an authorization to progress on the route from the ground station 50.

[0051] The progress authorization is in particular generated by the ground station 50 as a function of the coordinate P of the vehicle 3, and for example in addition of coordinates of other vehicles present on the predefined route, of a movement plan of the vehicle 3 on the route, etc.

[0052] When vehicle 3 does not receive authorization to proceed, it stops moving along the predefined route.

[0053] In order for the vehicle 3 to be able to move along the predefined route in good conditions, it is therefore necessary that communication between the vehicle 3 and the ground station 50 is ensured permanently.

[0054] When the vehicle 3 communicates with the ground station 50 via ground equipment 40, the vehicle 3 is said to be paired with said ground equipment 40.

[0055] By "communicating with the ground station" is meant that the vehicle 3 and the ground station 50 exchange the vehicle's P coordinate and any progress authorization by exchanging radio signals between the vehicle 3 and the ground equipment 40 with which the vehicle 3 is paired. In other words, the vehicle's P coordinate and any progress authorization are exchanged via the useful radio link between the vehicle 3 and the ground equipment 40 with which the vehicle 3 is paired.

[0056] When the communication between the vehicle 3 and the ground station 50 is compromised, in particular when the useful radio link between the vehicle 3 and the ground equipment 40 with which the vehicle 3 is paired is degraded, or in nominal operation when the vehicle has moved and the signal level on the useful radio link becomes too weak, the vehicle 3 is paired with another ground equipment 40 allowing the exchange of the coordinate P and any authorization to progress on the predefined route. This operation is called cellular transfer (in English "handover"). By "nominal operation", it is meant that there is no particular phenomenon causing an abnormal degradation of the useful radio link (which is to be distinguished from an attenuation of radio signals exchanged by the useful radio link due to an increasing distance between the vehicle 3 and the ground equipment 40 with which the vehicle 3 is paired).When the useful radio link is abnormally degraded and in particular when there is redundancy in the radio architecture, the secondary radio link can become a useful radio link as a replacement. This operation is also called cellular transfer (in English “handover”). The pairing of the vehicle 3 with another ground equipment 40 then makes it possible to ensure a continuous exchange of the coordinate P of the vehicle and of any authorization for progress between the vehicle 3 and the ground station 50, and therefore to ensure the smoothest possible progress of the vehicle 3 on the predefined route.

[0057] Each radio link between the vehicle 3 and a ground equipment 40, in particular each channel, is characterized by at least one parameter of interest Q. In particular, the parameter of interest Q is representative of the quality of the radio link, in particular of the corresponding channel, between the vehicle 3 and the corresponding ground equipment 40.

[0058] For example, the parameter of interest Q is the reception power level of a radio signal received by the vehicle 3 and transmitted from ground radio equipment 40 via the corresponding radio link, in particular the corresponding channel.

[0059] The parameter of interest Q is advantageously taken into account for carrying out the cellular transfer between the vehicle 3 and the various ground equipment 40.

[0060] In the following, as illustrated in the example of Figure 1, it is considered that the vehicle 3 is configured, at a given instant during its movement along the route, to be connected with a first ground equipment 40 via a useful radio link L1 to communicate with the ground station 50 and for example to be connected with a second ground equipment 40 via a secondary radio link L2. Of course, the invention also applies when the vehicle 3 is connected with more than two ground equipment 40 at the same time.

[0061] According to the example illustrated in Figure 1, the useful radio link L1 comprises a first channel C1 and a second channel C2. Here, the first channel C1 is a useful channel via which the vehicle 3 communicates with the ground station 50 and the second channel C2 is a secondary channel.

[0062] As illustrated in Figure 2, the vehicle 3 comprises a location device 10 and a radio signal communication device 12, connected to the location device 10.

[0063] The location device 10 is configured to generate location data, representative of the coordinate P of the vehicle 3. For example, the location device 10 is a GPS signal receiver or a ground beacon detection system whose locations are known and between which a wheel rotation and slip measurement system makes it possible, by interpolation, to determine the location of the vehicle 3.

[0064] The communication device 12 is able to be connected with the first and second ground equipment 40 by the respective radio links L1, L2. Furthermore, the communication device 12 is configured for communication with the ground station 50 via the first ground equipment 40, in particular by the useful radio link L1, in particular by the useful channel C1, with the first ground equipment 40.

[0065] The communication device 12 comprises a radio transceiver unit 16 and a central unit 18 connected to the radio transceiver unit 16.

[0066] The radio transceiver unit 16 is configured to exchange radio signals with the first and second ground equipment 40, in particular with the radio transceiver unit(s) 42 of the ground equipment 40, via the respective radio links L1, L2.

[0067] As illustrated in Figure 1, the radio transceiver unit 16 of the communication device 12 comprises for example a transceiver 19 and a physical antenna 20 connected to the transceiver 19. Advantageously, the radio transceiver unit 16 comprises at least two transceivers 19 and at least two physical antennas 20 to ensure path redundancy for the radio signals to the ground station 50. According to a variant not illustrated, the vehicle 3 comprises two radio transceiver units 16.

[0068] Advantageously, the radio transceiver unit 16 further comprises a device for measuring the power level in reception of radio signals received by the antenna 20 of the unit 16. The device for measuring the power level in reception of the received radio signals is in particular configured to generate power level measurement data.

[0069] Each radio transceiver unit 16 is for example uniquely associated with an identifier. This identifier is for example used by a module 28 of the communication device 12 of the vehicle 3 to generate any group of measurement data of the parameter of interest Q of any radio link between the vehicle 3 associated with said identifier of the radio transceiver unit 16 and the corresponding ground equipment 40. The identifier makes it possible to identify which equipment on board a vehicle carried out the measurement.

[0070] The communication device 12 is configured to transmit, among other things, to the ground equipment 40 with which the vehicle 3 is paired, i.e. the first ground equipment 40:

[0071] - measurements of the P coordinate of vehicle 3; and

[0072] - measurements of the parameter of interest Q of the radio link between the vehicle 3 and a ground device 40, here the first and / or the second ground device 40.

[0073] More generally, the operating mode of a mobile radio system involves the permanent measurement (at more or less close intervals) of all the channels on which a ground station is likely to transmit. The measurements may therefore concern a plurality of ground equipment. The communication device 12 on the vehicle may choose to connect to the ground equipment having the best signal. The measurements of the parameter of interest may therefore concern a plurality of ground equipment which are associated with each measurement by a unique identifier assigned to them.

[0074] These measurements are, for example, transmitted in real time. In other words, the measurements are transmitted as soon as they are taken. Alternatively, these measurements are stored on board the vehicle and transmitted later.

[0075] The communication device 12 is further configured to receive from the ground equipment 40 with which the vehicle 3 is paired, i.e. the first ground equipment 40, any authorization to progress generated by the ground station 50.

[0076] The communication device 12 comprises a module 28 for measuring the parameter of interest Q of the radio link between the vehicle 3 and one or more ground equipment 40, for example here the first and / or the second ground equipment 40, as a function of time, a module 30 for measuring the coordinate P of the vehicle 3 as a function of time and a module 32 for managing the radio links.

[0077] The modules 28, 30 and 32 are, for example, software modules comprising software code instructions recordable on a memory and executable by a processor. Alternatively, at least one of the modules 28, 30 and 32 is provided in the form of a programmable logic component or a dedicated integrated circuit.

[0078] The central unit 18 of the communication device 12 of the vehicle 3 comprises, for example, a processor 22 and a memory 24 containing the modules 28, 30 and 32 provided in the form of software modules capable of being executed by the processor 22.

[0079] In one variant, the module 28 is integrated into the transceiver 19 of the radio transceiver unit 16.

[0080] The module 28 is configured to measure the parameter of interest Q of the radio link between the vehicle 3 and a ground equipment 40, here the first and / or the second ground equipment 40, as a function of time. In particular, the module 28 is configured to measure the parameter of interest Q of each channel of the radio link between the vehicle 3 and a ground equipment 40 as a function of time. In other words, the module 28 is configured to measure not only the parameter of interest Q of the useful radio link L1, in particular of the useful channel C1, through which the information passes, but also the parameter of interest Q of each secondary radio link L2 or of each secondary channel C2, in order to enable cell handover decisions to be made.

[0081] In particular, the module 28 is configured to receive the power level measurement data from the radio transceiver unit 16, in particular from the device for measuring the power level in reception of the radio signals received by the antenna 20 of the unit 16.

[0082] Typically, measurements of the parameter of interest Q are used to make pairing change decisions to ground equipment 40 based on the signal level of the one to which the vehicle 3 is paired. Typically, these measurements or a sub-sampling thereof will be used for the purposes of the invention. The sub-sampling is chosen so as to preserve the essential characteristics of the signal as a function of the location.

[0083] A first typical time interval between two measurements of the parameter of interest Q is for example between 10 ms and 40 ms, in particular substantially equal to 20 ms. Thus, by way of example, the module 28 is configured to measure the parameter of interest Q of the radio link between the vehicle 3 and a ground equipment 40, here the first and / or the second ground equipment 40, every 20 ms.

[0084] Other interesting parameters for assessing radio quality can be measured, for example the time taken to make a cellular transfer (change of pairing), packet losses, the measured throughput, latency (round trip time of a radio signal between the vehicle 3 and the ground equipment 40).

[0085] As mentioned above, the parameter of interest Q of the radio link is taken into account to determine a possible change of pairing between the vehicle 3 and the ground equipment 40 (cellular handover).

[0086] For example, if the parameter of interest Q of the useful radio link is representative of an unsatisfactory signal for the exchange of the coordinate P of the vehicle 3 and of any authorization to progress, the vehicle 3 is paired, if necessary, with other ground equipment 40 for which the parameter of interest Q of the radio link is representative of a satisfactory signal for said exchange.

[0087] In a particular example, if the power level in reception of a radio signal exchanged by the useful radio link is lower than a predetermined threshold, the vehicle 3 subsequently communicates, if necessary, with the ground station 50 via another ground equipment 40, therefore via another radio link, in particular for which the power level in reception of radio signals exchanged by said other radio link is higher than the predetermined threshold.

[0088] For example, the module 28 is configured to generate, for each measurement of the parameter of interest Q, a group of measurement data of the parameter of interest Q, each group of measurement data of the parameter of interest Q comprising:

[0089] - an identifier of the ground equipment 40 involved, in particular of the radio transmission-reception unit 42 of the ground equipment 40 involved; - the value of the measured parameter of interest Q; and

[0090] - the time at which the measurement of the parameter of interest Q was carried out.

[0091] The module 30 is configured to receive the location data from the location device 10.

[0092] The module 30 is configured to measure the coordinate P of the vehicle 3 as a function of time, from the location data, in particular with a second time interval which is for example constant between the measurements. The second time interval is for example between 400 ms and 800 ms, in particular substantially equal to 600 ms. Thus, by way of example, the module 30 is configured to measure the coordinate P of the vehicle 3 every 600 ms.

[0093] For example, the module 30 is configured to generate for each measurement of the coordinate P of the vehicle, a group of measurement data of the coordinate P, each group of measurement data of the coordinate P comprising:

[0094] - a rank number of the measurement relative to the order of all the P coordinate measurements carried out;

[0095] - the value of the measured P coordinate;

[0096] - the time at which the measurement of the P coordinate was carried out.

[0097] Advantageously, each group of measurement data of the coordinate P further comprises:

[0098] - the speed of vehicle 3; and

[0099] - the direction of movement of the vehicle 3.

[0100] Advantageously, the radio link management module 32 is capable of changing the ground equipment 40 with which the vehicle 3 is paired, in particular as a function of the parameter of interest Q of the useful radio link, and of the parameter of interest Q of the secondary radio link.

[0101] In particular, when the reception power level of a radio signal exchanged by the useful radio link is lower than the predetermined threshold and when the reception power level of a radio signal exchanged by the secondary radio link is higher than the predetermined threshold, the radio link management module 32 controls the radio transceiver unit 16 so that the vehicle 3 is unpaired from the first ground equipment 40 and is paired with the second ground equipment 40.

[0102] The radio link management module 32 is further configured to control the radio transceiver unit 16 of the vehicle 3 so that the latter transmits the measurement of the parameter of interest Q to each radio transceiver unit 42 of the ground equipment 40 with which the vehicle 3 is paired. In particular, the radio link management module 32 is configured to control the radio transceiver unit 16 of the vehicle 3 so that the latter transmits the groups of measurement data of the parameter of interest Q to the ground equipment 40 with which the vehicle 3 is paired, in other words via the useful radio link, for example, in real time. Alternatively, these data are for example stored on board the vehicle 3 and transmitted later.

[0103] For example, the radio link management module 32 is configured to control the radio transceiver unit 16 of the vehicle 3 so that the latter transmits the data groups of the parameter of interest Q determined successively with the first time interval between the determinations.

[0104] The radio link management module 32 is further configured to control the radio transceiver unit 16 of the vehicle 3 so that the latter transmits the coordinate measurement P of the vehicle 3 as a function of time, to each radio transceiver unit 42 of the ground equipment 40 with which the vehicle 3 is paired.

[0105] In particular, the radio link management module 32 is configured to control the radio transceiver unit 16 of the vehicle 3 so that the latter transmits the groups of measurement data of the coordinate P to the ground equipment 40 with which the vehicle 3 is paired.

[0106] For example, the radio link management module 32 is configured to control the radio transceiver unit 16 of the vehicle 3 so that the latter transmits the groups of measurement data of the coordinate P successively at second regular time intervals.

[0107] Each ground equipment 40 is uniquely associated with an identifier. As explained above, this identifier is used by the module 28 of the communication device 12 of the vehicle 3 to generate any group of measurement data of the parameter of interest Q of any radio link between the vehicle 3 and the ground equipment 40 associated with said identifier.

[0108] For example, the unique identifier of the radio transceiver unit 16 is transmitted with the measurements and makes it possible to match these measurements with the vehicle 3 and in particular the module 28.

[0109] As mentioned above, each ground equipment 40 comprises at least one radio transceiver unit 42 with which the vehicle 3 is intended to exchange radio signals.

[0110] Advantageously, each ground equipment 40 comprises at least two radio transceiver units 42 each configured to provide substantially identical radio coverage. For example, these radio transceiver units 42 are substantially identical and advantageously substantially located at the same location. According to a particular example, each ground equipment 40 comprises exactly two units 42.

[0111] Advantageously, each radio transceiver unit 42 of each ground equipment 40 is uniquely associated with an identifier. This identifier is notably also used by the module 28 of the communication device 12 of the vehicle 3 to generate any group of measurement data of the parameter of interest Q of any radio link between the vehicle 3 and the radio transceiver unit 42 associated with said identifier. The identifier of the radio transceiver unit 42 makes it possible to identify which ground equipment transmitted the signal which is measured.

[0112] Each radio transceiver unit 42 of the same ground equipment 40 with which the vehicle 3 is paired is intended to receive the measurements of the parameters of interest Q and the coordinate measurements P of the vehicle 3, transmitted by the radio transceiver unit 16 of the vehicle 3.

[0113] Each ground equipment 40 is configured to transmit the measurement of the parameter of interest Q as a function of time and the measurement of the coordinate P of the vehicle 3 as a function of time, emitted by the radio transceiver unit 16 of the vehicle 3, to the ground station 50.

[0114] According to the example illustrated in the present application, the ground station 50 comprises a server configured to receive the measurement data. Optionally, the ground station 50 further comprises a signaling server, configured to administer the movement of the vehicle 3 along the route, in particular to generate authorizations for progress on the route. Alternatively, the ground station 50 comprises an internet access server configured to provide internet access to the passengers located in the vehicle 3. According to another alternative, the ground station 50 comprises a security server capable of processing security-related data (video surveillance images, passenger information) generated or processed by dedicated equipment on board the vehicle 3.

[0115] In a particular example, the measurement data is stored in a remote storage server. In particular, a remote processing server has remote access to the storage server to retrieve the data and perform its processing.

[0116] In one implementation, the ground station 50 comprises a characterization assembly 52 configured for characterizing the quality of the radio link between the vehicle 3 and the ground equipment 40, here the first and / or second ground equipment 40. The characterization assembly 52 comprises a storage module 60, a module 62 for calculating a reading REL of the parameter of interest Q of a radio link as a function of the coordinate P of the vehicle, a module 64 for calculating a reference curve REF of the parameter of interest Q of a reference radio link as a function of the coordinate P of the vehicle and a module 70 for characterizing the quality of this radio link.

[0117] Advantageously, the characterization assembly 52 further comprises a database 66 grouping together data relating to the vehicle 3 and the ground equipment 40 and a module 68 for preparing the data relating to the vehicle 3 and the ground equipment 40.

[0118] The storage module 60 is configured to store the measurements of the parameters of interest Q as a function of time and the measurements of the coordinate P of the vehicle 3 as a function of time.

[0119] In particular, the storage module 60 is configured to store the measurement data groups of the parameter of interest Q and the measurement data groups of the coordinate P of the vehicle 3.

[0120] The module 62 is configured to calculate the reading REL of the parameter of interest Q as a function of the coordinate P of the vehicle 3, from the measurements of the parameter of interest Q as a function of time and the measurements of the coordinate P of the vehicle 3 as a function of time.

[0121] In particular, the module 62 is configured to generate a function representative of the values ​​of the parameter of interest Q as a function of time from the groups of measurement data of the parameter of interest Q stored in the storage module 60, in particular from the values ​​of the measured parameter of interest Q and the times at which the measurements of the parameter of interest Q were carried out. The module 62 is further configured to generate a function representative of the values ​​of the coordinate P of the vehicle as a function of time from the groups of measurement data of the coordinate P stored in the storage module 60, in particular from the values ​​of the measured coordinate P and the times at which the measurements of the coordinate P were carried out.

[0122] Advantageously, the module 62 is further configured to synchronize the function representing the values ​​of the parameter of interest Q as a function of time and the function representing the values ​​of the coordinate P of the vehicle 3 as a function of time. Indeed, the clocks of the capture systems as a function of time, on the one hand, of the parameter of interest Q and, on the other hand, of the coordinates P of the vehicle 3, are not necessarily synchronized. The ex-post synchronization of the captured data then makes it possible to process them jointly. In particular, the module 62 is configured to synchronize the functions by associating the longest plateau of the function representing the values ​​of the coordinate P of the vehicle as a function of time with the longest portion of the function representing the values ​​of the parameter of interest Q measured as a function of time for which the variance of the value of the parameter of interest Q is minimal.In particular, this plateau is representative of a long stop of vehicle 3.

[0123] According to a variant, the module 62 is configured to synchronize the functions by associating a plurality of consecutive plateaus of the function representative of the values ​​of the coordinate P of the vehicle as a function of time with a plurality of portions of the function representative of the values ​​of the parameter of interest Q measured as a function of time for which the variance of the value of the parameter of interest Q is minimal. In particular, these plateaus are representative of successive stops of the vehicle 3.

[0124] Still advantageously, the module 62 is configured to associate the parameter of interest Q at a given instant with the coordinate P of the vehicle 3 at the given instant by interpolation in the time domain of the function representative of the values ​​of the parameter of interest Q measured as a function of time and of the function representative of the values ​​of the coordinate P of the vehicle 3 as a function of time.

[0125] In particular, the module 62 is configured to calculate the reading REL of the parameter of interest Q as a function of the coordinate P of the vehicle 3, from the functions respectively representative of the values ​​of the parameter of interest Q as a function of time and of the values ​​of the coordinate P of the vehicle 3 as a function of synchronized time.

[0126] If the parameter of interest Q is carried by the information linked to the position (for example the parameter of interest Q will be the sequence number of the location messages) conversely the interpolation of the radio measurements makes it possible to know to which ground radio equipment the vehicle was connected when these messages were received, and what the quality of the link was.

[0127] Two REL readings of the parameter of interest Q as a function of the coordinate P of vehicle 3 are illustrated as an example in Figure 3. The parameter of interest Q is expressed in dBm and the coordinate P is expressed in m.

[0128] A first REL reading corresponds to the radio link between the vehicle 3 and ground equipment 40 during a first pass of the vehicle 3 near the ground equipment 40, and a second REL reading corresponds to the radio link between the vehicle 3 and the same ground equipment 40 during a second pass of the vehicle 3 near the ground equipment 40. Alternatively, the second reading corresponds to the passage of another vehicle near the ground equipment 40: if the vehicles have the same radio equipment on board, in principle the readings will be substantially identical. If the readings are not substantially identical, this matching of several readings obtained by vehicles makes it possible to highlight malfunctions of radio equipment on board the vehicle and the other vehicle.

[0129] The module 64 is configured to calculate the reference curve REF of the parameter of interest Q of a reference radio link between the vehicle 3 and ground equipment 40, in particular the ground equipment 40 for which the quality of the radio link is to be characterized, in particular as a function of the coordinate P of the vehicle 3.

[0130] The reference curve REF is representative of an optimal radio signal exchange between the vehicle 3 and the ground equipment 40 via the reference radio link.

[0131] For example, the module 64 is configured to calculate the reference curve REF from measurements of the parameter of interest Q and measurements of coordinate P taken when the vehicle 3 is traveling in optimal conditions and when the radio transceiver units 42 of the ground equipment 40 and the radio transceiver unit 16 of the vehicle 3 are precisely calibrated.

[0132] A reference curve REF is illustrated as an example in Figure 3. In Figure 3, the reference curve REF corresponds substantially to the reference radio link between the vehicle 3 and the ground equipment 40 to which the first and second illustrated REL readings correspond.

[0133] The database 66 contains data relating to the vehicle 3, in particular to the communication device 12 of the vehicle 3, and data relating to the ground equipment 40.

[0134] For example, the data stored in the database 66 are data relating to the technical characteristics of the radio transceiver unit 16 of the vehicle 3 and the radio transceiver units 42 of the ground equipment 40 (structural characteristics, settings, etc.), data relating to the positions of the radio transceiver units 42 of the ground equipment 40, data relating to the environments around the radio transceiver units 42 of the ground equipment 40 (surrounding environments or nearby transmitting devices influencing the propagation of the signals) and data relating to the identifiers of the ground equipment 40, in particular the radio transceiver units 42 of the ground equipment 40, data relating to the geographical and operational environment (for example in the case of lengths and structures of the tracks, position of the platforms, size and configuration of the tunnels, etc.).

[0135] The preparation module 68 is configured to format the data contained in the database 66 so that they can be used by the characterization module 60. The preparation module 68 is, in particular, configured to generate a database prepared from the database 66, the data of which is suitable for use by the characterization module 70 to characterize the quality of the radio link.

[0136] The characterization module 70 is configured to characterize the quality of the radio link between the vehicle 3 and the ground equipment 40, by comparing the reading REL of the parameter of interest Q with the reference curve REF of the parameter of interest Q.

[0137] The characterization module 70 is in particular configured to characterize the quality of the radio link on the basis of the data prepared from the database 66 by the preparation module 68.

[0138] The characterization module 70 comprises, for example, a sub-module 74 for calculating at least one radio link quality indicator, a diagnostic sub-module 76 and a prognosis sub-module 78.

[0139] Advantageously, the sub-module 74 is configured to calculate the at least one quality indicator. The at least one quality indicator is a variable having a value representative of a satisfactory quality of the radio link or a value representative of a degraded quality of the radio link.

[0140] For example, the variable takes a binary value depending on whether the quality is satisfactory or degraded. In one specific example, when the quality is satisfactory, the quality indicator is 1 and when the quality is degraded, the quality indicator is 0. In a variant, the variable takes a continuous value corresponding to a "distance" calculated between the reference curve and the reading.

[0141] Advantageously, the sub-module 74 is configured to calculate a first quality indicator. In particular, to calculate the first quality indicator, the sub-module compares a decomposition of the REL reading of the parameter of interest Q into components calculated by principal component analysis and a decomposition of the reference curve REF of the parameter of interest Q into components calculated by principal component analysis.

[0142] In particular, the REL survey of the parameter of interest Q and the reference curve REF of the parameter of interest Q are respectively decomposed into a linear combination of basis functions. The REL survey of the parameter of interest Q and the reference curve REF of the parameter of interest Q are then characterized by the coefficients of their respective linear combinations. The vector comprising the coefficients of the linear combination of the REL survey of the parameter of interest Q and the vector comprising the coefficients of the linear combination of the reference curve REF of the parameter of interest Q are respectively called survey signature and reference signature.The sub-module 74 is in particular configured to calculate a mathematical distance between the recorded signature and the reference signature, in other words between the vector comprising the coefficients of the linear combination of the recording REL of the parameter of interest Q and the vector comprising the coefficients of the linear combination of the reference curve REF of the parameter of interest Q. The distance is for example the Minkowski distance.

[0143] For example, when the distance between the detected signature and the reference signature is greater than a predetermined distance threshold, the sub-module 74 associates a value representative of degraded quality with the first quality indicator and when the distance between the signature and the reference signature is less than the predetermined distance threshold, the sub-module 74 associates a value representative of satisfactory quality with the first quality indicator. The predetermined distance threshold is advantageously chosen so as to minimize the false positive rate.

[0144] Still advantageously, the sub-module 74 is configured to compare the REL reading of the parameter of interest Q corresponding to the first channel of the radio link and the REL reading of the parameter of interest Q corresponding to the second channel of the radio link. The radio coverages of the radio transceiver units 42 of the ground equipment 40 being substantially identical, the REL readings of the parameter of interest Q of the first and second channels of the radio link should be identical. A difference between the REL readings of the parameter of interest Q of the first and second channels indicates a degradation in the quality of a channel of the radio link.

[0145] Advantageously, the sub-module 74 is capable of recognizing the absence of a group of measurement data of the coordinate P of the vehicle in the storage module 60 of the ground station 50. Such an absence results for example from a failure to transmit a measurement of coordinate P of the vehicle 3 from the vehicle 3 to the ground equipment 40 with which the vehicle 3 is paired.

[0146] In particular, the sub-module 74 is capable of recognizing the absence of a group of measurement data of the coordinate P of the vehicle 3 when the storage module 60 of the ground station 50 does not store any group of measurement data of the coordinate P with a rank number n and the storage module 60 of the ground station 50 stores two groups of measurement data of the coordinate P with rank numbers n-1 and n+1 respectively. The sub-module 74 then recognizes that the n-th measurement of the coordinate P of the vehicle 3 never reached the ground station 50. Similarly, it is possible to detect the absence of several consecutive groups of data (for example between n-1 and n+5 representing the loss of 5 consecutive groups of data). Advantageously, the sub-module 74 is configured to calculate at least one other quality indicator, in particular when the sub-module 74 recognizes the absence of a group of measurement data of the coordinate P.The at least one second quality indicator is, for example, a function of the percentage of lost location messages associated with the REL reading during the passage of vehicle 3. This indicator will make it possible to enrich and improve the characterization of the quality of the radio link.

[0147] According to a particular example, the sub-module 74 is furthermore capable of associating each value representative of a degraded quality of a quality indicator with a ground equipment 40, in particular with a radio transceiver unit 42 of the ground equipment 40, by associating said value of the quality indicator with the identifier of the ground equipment 40 taken from the group of measurement data of the parameter of interest Q having led to the calculation of said value of the quality indicator. This thus makes it possible to distinguish the ground equipment 40 for which the radio link is degraded.

[0148] Advantageously, the sub-module 74 is further configured to calculate other quality indicators, for example a second quality indicator, as a function of packet losses, the measured throughput, the latency, the speed of the vehicle 3, etc. These indicators will make it possible to strengthen the characterization of the quality of the radio link and to characterize its impact on the applications which use this link.

[0149] Advantageously, when the value of one or more quality indicator(s) is(are) representative of degraded quality, in particular when the value of the first quality indicator is representative of degraded quality, the diagnostic sub-module 76 is configured to determine a cause of the degradation.

[0150] A cause of degradation is, for example, degradation of the electronics of the radio transceiver units 42, incorrect orientation of one or more antenna(s) 44 of the radio transceiver units 42, incorrect configuration of the radio transceiver units 42, an interference phenomenon, etc.

[0151] Advantageously, the diagnostic sub-module 76 is capable of accessing a database relating to different causes of radio link degradation. The data relating to different causes of degradation are, for example, obtained by simulation or in real cases by deliberately provoking the cause of degradation during tests of the vehicle 3 and / or the ground equipment 40.

[0152] The data relating to the different causes of degradation include, for example, associations between causes of degradation and typical curves of the parameter of interest Q as a function of the coordinate P of the vehicle 3, corresponding to said causes of degradation. Also advantageously, the diagnostic sub-module 76 is configured to recognize the cause of the degradation of the radio link by comparing the REL reading of the parameter of interest Q with the typical curves of the parameter of interest Q corresponding to the different causes of degradation.

[0153] For example, the diagnostic sub-module 76 is configured to compare a decomposition of the REL reading of the parameter of interest Q into components calculated by principal component analysis and the decompositions of the typical curves of the parameter of interest Q corresponding to the different causes of degradation into components calculated by principal component analysis.

[0154] Alternatively or optionally, the diagnostic sub-module 76 is configured to determine the cause of the degradation of the radio link based on the average of the difference between the reading REL of the parameter of interest Q and the reference curve REF of the parameter of interest Q.

[0155] In particular, when the average of the difference between the reading REL of the parameter of interest Q and the reference curve REF of the parameter of interest Q is substantially constant (in other words when the reading REL is approximately shifted by a constant value relative to the reference curve REF), the diagnostic sub-module 76 determines that the parameter of interest Q is attenuated constantly along the curve. The diagnostic sub-module 76 then determines that the cause of degradation is for example damage to a power amplifier of the radio transceiver unit 42, damage to a connector between the radio transceiver unit 42 and its antenna 44, or a change in the transmission power parameter of the radio transceiver unit 42.

[0156] Advantageously, these cases can be distinguished by an analysis of the temporal evolution of the difference: for example, a change in the transmission power parameter will correspond to a sudden change, whereas damage to a connector will probably result in a slow and progressive degradation.

[0157] Alternatively or optionally, the diagnostic sub-module 76 is configured to determine the cause of the degradation of the exchanged radio signal based on the variance of the difference between the reading REL of the parameter of interest Q and the reference curve REF of the parameter of interest Q.

[0158] Alternatively or optionally, the diagnostic sub-module 76 is configured to determine which physical antenna 44 is degraded in the case where the ground transceiver unit 42 comprises two physical antennas 44 each aimed, for example, at an opposite side of the track on which the vehicle 3 is moving. Typically in this case, the signal coming out of the radio transceiver unit 42 is connected to a radio cable itself connected to a divider (or “splitter” in English) which divides the signal in two and allows two radio cables to be connected to each antenna 44. In this case, it will be possible, for example, to detect that one of the two physical antennas 44 has a problem if only the curve which corresponds to it is degraded.

[0159] Alternatively or optionally, the diagnostic sub-module 76 is configured to detect that the degradation comes from the change in pointing of the antenna (typically if the antenna has been incorrectly screwed, it will gradually tilt downwards). By simulation, the diagnostic sub-module 76 can estimate the deformation that the reference curve REF or the reading REL would undergo for different tilt angles. By comparison between the simulated curve and the observed curve, the diagnostic sub-module can then detect the problem and approximately quantify the tilt.

[0160] Alternatively or optionally, the diagnostic sub-module 76 is configured to detect that the degradation comes from a new obstacle on the radio propagation path. The REL reading will then be distorted relative to the REF reference curve. The diagnostic sub-module 76 is then able to indicate the most likely cause of deterioration as being a new obstacle by ruling out a possible change in inclination (using simulation or by detecting a constant offset).

[0161] Advantageously, the diagnostic sub-module 76 is configured to modify the database relating to the causes of degradation by associating a REL reading of the parameter of interest Q with a cause of degradation. If, for example, machine learning algorithms are used for the detection and diagnosis of degradation, it will be able to reinforce itself (reinforcement learning) on ​​the basis of this information and automatically improve its accuracy.

[0162] Advantageously, the diagnostic sub-module 76 is configured to determine the cause of degradation furthermore on the basis of direct or indirect interference measurements carried out along the route. Typically, a high level of interference, for example higher than the level of a useful signal by less than 10 dB, does not modify the REL reading if it comes from the measurement of the received signal level. On the other hand, a high level of interference degrades secondary quality indicators which can be measured for example simultaneously, such as for example the noise level or signal-to-noise ratio, the radio quality indicator as measured on 4G networks (RSRQ for “Reference Signal Received Quality”), or application indicators such as packet losses or the reduction in throughput. In addition and as an option, the interference can be measured explicitly, possibly by dedicated radio modules.The combination of these measurements makes it possible to conclude that interference is present and to locate it approximately.

[0163] Advantageously, the diagnostic sub-module 76 comprises a complete machine learning processing chain configured to integrate all of the measurements into its processing to automatically provide accurate diagnoses.

[0164] Advantageously, the prognosis, therefore the prediction of the temporal evolution of the degradations, will be carried out by the analysis of the temporal evolution of the indicators linked to the diagnosis.

[0165] In particular, when the value of the at least one quality indicator, in particular the first quality indicator, is representative of a satisfactory quality but tends over time towards a value representative of a degraded quality of the radio signal received by the vehicle, the prognosis sub-module 78 is configured to determine a duration at the end of which the value of the at least one quality indicator will be representative of a degraded quality of the radio signal received by the vehicle 3.

[0166] Advantageously, the characterization assembly further comprises a module 72 for establishing a report on the quality of the radio links.

[0167] The module 72 is configured to record for each radio link between the vehicle and the radio transceiver units 42 of the ground equipment 40, the at least one quality indicator calculated by the sub-module 74, where applicable the cause of degradation of the corresponding radio link determined by the diagnostic sub-module 76, and / or where applicable the duration after which the value of the at least one quality indicator will be representative of a degraded quality of the radio link determined by the prognosis sub-module 78.

[0168] The modules 60, 62, 64, 66, 68, 70 and 72 are for example provided in the form of software applications recordable on a memory 56 and executable by a processor 54. Alternatively, at least one of these modules 60, 62, 64, 66, 68, 70 and 72 is provided in the form of a programmable logic component or a dedicated integrated circuit.

[0169] In an exemplary embodiment, the characterization assembly 52 is integrated into the ground station 50, which comprises for example a processor 54 and a memory 56 containing the software modules 60, 62, 64, 66, 68, 70 and 72 suitable for being executed by the processor 54.

[0170] In another exemplary embodiment, the characterization assembly 52 is virtualized and implemented using the physical resources of one or more computer equipment, each located in the ground station 50 or remotely. In the following, with reference to FIG. 4, a method 100 for characterizing the quality of a radio link between the vehicle 3 and at least one ground equipment 40 is described.

[0171] The vehicle 3 is connected with a first ground equipment 40 via a useful radio link for communicating with the ground station 50. The measurement of the parameter of interest Q is carried out on all the ground equipment 40 whose signal can be received and decoded to be taken into account to determine the ground equipment 40 with which the vehicle 3 will be connected via the useful radio link.

[0172] For the sake of clarity and conciseness, it is considered that the vehicle 3 is further connected with a second ground equipment 40 via a secondary radio link.

[0173] The method 100 comprises a first step 110 of measuring the parameter of interest Q of a radio link between the vehicle and a ground device 40, here the first or second ground device 40, as a function of time.

[0174] Advantageously, the first step 110 is carried out by the module 28 of the communication device 12 of the vehicle 3.

[0175] Here, the measurement of the parameter of interest Q of the radio link is carried out by the vehicle 3 to be taken into account to determine the ground equipment 40 through which the vehicle 3 communicates with the ground station 50.

[0176] For example, the parameter of interest Q is measured with a constant first time interval between measurements.

[0177] Advantageously, the first step 110 comprises the measurement of the parameter of interest Q of the first channel connecting the first radio transceiver unit 42 as a function of time and the measurement of the parameter of interest Q of the second channel connecting the second radio transceiver unit 42 as a function of time.

[0178] The method then comprises a second step 120 of measuring the coordinate P of the vehicle 3 as a function of time.

[0179] For example, the P coordinate of vehicle 3 is measured with a second constant time interval between measurements.

[0180] Advantageously, the second step 120 is carried out by the module 30 of the communication device 12 of the vehicle 3.

[0181] Here, the measurement of the coordinate P of the vehicle 3 is carried out by the vehicle 3 to receive an authorization for the vehicle 3 to progress on the predefined route from the ground equipment 40 with which the vehicle is paired, the authorization for progress being issued by the ground station 50. The measurements of the parameter of interest Q and the measurements of the coordinate P are transmitted by the vehicle 3 to the ground station 50 via the ground equipment 40 with which the vehicle 3 is paired, in other words via the useful radio link.

[0182] For example, the radio transceiver unit 16 of the vehicle 3 transmits the data groups of the parameter of interest Q and the measurement data groups of the coordinate P to the ground equipment 40 with which the vehicle 3 is paired, in particular to the ground station 50.

[0183] The measurements of the parameters of interest Q as a function of time and the measurements of the coordinate P of the vehicle 3 as a function of time, in particular the groups of measurement data of the parameter of interest Q and the groups of measurement data of the coordinate P of the vehicle 3, are stored in the storage module 60 of the ground station 50.

[0184] The method then comprises a third step 130 of calculating the reading REL of the parameter of interest Q as a function of the coordinate P of the vehicle 3 from the measurement of the parameter of interest Q as a function of time and the measurement of the coordinate P of the vehicle as a function of time.

[0185] Advantageously, the third step 130 is carried out by the module 62 of the characterization assembly 52.

[0186] In particular, during the third step 130, the module 62 generates a function representative of the values ​​of the parameter of interest Q as a function of time from the groups of measurement data of the parameter of interest Q stored in the storage module 60, in particular from the values ​​of the measured parameter of interest Q and the times at which the respective measurements of the parameter of interest Q were carried out. During the third step 130, the module 62 further generates a function representative of the values ​​of the coordinate P of the vehicle as a function of time from the groups of measurement data of the coordinate P stored in the storage module 60, in particular from the values ​​of the measured coordinate P and the times at which the respective measurements of the coordinate P were carried out.

[0187] For example, the third step 130 comprises the synchronization of the function representing the values ​​of the parameter of interest Q measured as a function of time and the function representing the values ​​of the coordinate P of the vehicle 3 as a function of time by associating the longest plateau of the function representing the values ​​of the coordinate P of the vehicle as a function of time with the longest portion of the function representing the values ​​of the parameter of interest Q measured as a function of time for which the variance of the value of the parameter of interest Q is minimal.According to a variant, the third step 130 comprises the synchronization of the function representative of the values ​​of the parameter of interest Q measured as a function of time and the function representative of the values ​​of the coordinate P of the vehicle 3 as a function of time by associating a plurality of consecutive plateaus of the function representative of the values ​​of the coordinate P of the vehicle as a function of time with a plurality of portions of the function representative of the values ​​of the parameter of interest Q measured as a function of time for which the variance of the value of the parameter of interest Q is minimal.

[0188] Advantageously, the third step 130 further comprises the association of the parameter of interest Q of the radio link at a given instant with the coordinate P of the vehicle 3 at the given instant by interpolation in the time domain of the function representative of the values ​​of the parameter of interest Q measured as a function of time and of the function representative of the values ​​of the coordinate P of the vehicle 3 as a function of time.

[0189] In particular, during the third step 130, the module 62 calculates the reading REL of the parameter of interest Q as a function of the coordinate P of the vehicle 3, from the functions respectively representative of the values ​​of the parameter of interest Q as a function of time and of the values ​​of the coordinate P of the vehicle 3 as a function of synchronized time.

[0190] Subsequently, the method comprises a fourth step 140 of calculating the reference curve REF of the parameter of interest Q of a reference radio link between the vehicle 3 and the ground equipment 40 as a function of the coordinate P of the vehicle 3.

[0191] Advantageously, the fourth step 140 is carried out by the module 64 of the characterization assembly 52.

[0192] In particular, the module 64 calculates the reference curve REF from measurements of the parameter of interest Q and measurements of coordinate P taken when the vehicle 3 is traveling in optimal conditions and when the radio transceiver units 42 of the ground equipment 40 and the radio transceiver unit 16 of the vehicle 3 are precisely calibrated.

[0193] Then, the method comprises a fifth step 150 of characterizing the quality of the radio link between the vehicle 3 and the ground equipment 40 by comparing the reading REL of the parameter of interest Q with the reference curve REF of the parameter of interest Q. As detailed below, the fifth step 150 notably comprises the detection, diagnosis and prognosis of faults affecting the radio link.

[0194] Advantageously, the fifth step is carried out by the characterization module 70 of the characterization assembly 52.

[0195] Advantageously, the characterization of the quality of the radio link is carried out by artificial intelligence. For example, the fifth step 150 comprises a sub-step of calculating the at least one quality indicator of the radio link. The sub-step of calculating the at least one quality indicator corresponds in particular to the detection of faults affecting the radio link.

[0196] The sub-step of calculating the at least one quality indicator is advantageously carried out by the sub-module 74 of the characterization module 70 of the characterization assembly 52.

[0197] Here, the sub-step of calculating the at least one quality indicator, in particular the first quality indicator, comprises a comparison of the decomposition of the REL reading of the parameter of interest Q into components calculated by principal component analysis and a decomposition of the reference curve REF of the parameter of interest Q into components calculated by principal component analysis.

[0198] In particular, during the sub-step of calculating the at least one quality indicator, the sub-module 74 calculates a mathematical distance between the signature and the reference signature, in other words between the vector comprising the coefficients of the linear combination of the REL reading of the parameter of interest Q and the vector comprising the coefficients of the linear combination of the reference curve REF of the parameter of interest Q.

[0199] For example, the sub-step of calculating the at least one quality indicator, in particular the first quality indicator, further comprises a comparison of the REL reading of the parameter of interest Q corresponding to the first channel of the radio link with the REL reading of the parameter of interest Q corresponding to the second channel of the radio link.

[0200] Advantageously, during the fifth step 150, the sub-module 74 recognizes any absence of a group of measurement data of the coordinate P of the vehicle in the storage module 60 of the ground station 50. When the sub-module 74 recognizes the absence of a group of measurement data of the coordinate P, the sub-module 74 calculates another quality indicator and associates with it a value representative of degraded quality.

[0201] Advantageously, when the value of one or more quality indicators is (are) representative of a degraded quality of the radio link, in particular when the value of the first quality indicator is representative of a degraded quality, the fifth step 150 comprises a sub-step of determining a cause of the degradation of the radio link. The sub-step of determining the cause of the degradation of the radio link corresponds in particular to the diagnosis of the faults affecting the radio link.

[0202] The determination sub-step is carried out in particular by the diagnostic sub-module 76.

[0203] For example, the diagnostic sub-module 76 accesses the database relating to different causes of degradation. The diagnostic sub-module 76 recognizes the cause of the degradation by comparing the REL reading of the parameter of interest Q with the typical curves of the parameter of interest Q corresponding to the different causes of degradation.

[0204] Advantageously, when the value of the at least one quality indicator, in particular the first quality indicator, is representative of satisfactory quality but tends over time towards a value representative of degraded quality, the fifth step 150 further comprises a sub-step of determining a duration at the end of which the value of the quality indicator will be representative of degraded quality. The sub-step of determining a duration at the end of which the value of the quality indicator will be representative of degraded quality corresponds in particular to the prognosis of the faults affecting the radio link.

[0205] For example, the fifth step 150 further comprises the calculation of at least one other second quality indicator as a function of the time taken to make a cellular transfer, packet losses, measured flow rates, latencies and / or the speed of the vehicle 3.

[0206] For example, the fifth step 150 further comprises taking into account additional analysis data provided such as the level of interference, the duration of the change of radio link (“handover” in English), the throughput observed on the radio link.

[0207] Advantageously, between the fourth step 140 and the fifth step 150, the method 100 comprises an intermediate step of preparing the data stored in the database 66 by the preparation module 68. During the fifth step 150, the characterization of the quality of the radio link is then carried out on the basis of the prepared data.

[0208] Optionally, during a sixth step 160, the module 72 records for each radio link between the vehicle and the radio transceiver units 42 of the ground equipment 40, the at least one quality indicator calculated by the sub-module 74, where applicable the corresponding cause of degradation determined by the diagnostic sub-module 76, and / or where applicable the duration after which the value of the quality indicator will be representative of a degraded quality determined by the prognosis sub-module 78. The elements stored in the module 72 are capable of being analyzed by an operator to learn the quality of the radio link between the vehicle 3 and the ground equipment 40.

[0209] The characterization method is implemented by an electronic characterization device, and in particular the steps of calculating a REL reading, calculating a reference curve and characterizing the radio link. Advantageously, the invention described above lends itself to any automated analysis that machine learning allows.

[0210] According to a variant, the module 28 of the device 12 is a module for measuring the parameter of interest Q as a function of the coordinate of the vehicle 3.

[0211] The module 62 is then configured to calculate the reading REL of the parameter of interest Q from the measurements of the parameter of interest Q as a function of the coordinate of the vehicle 3 and the measurements of the coordinate P of the vehicle 3 as a function of time.

[0212] The module 62 is then advantageously configured to associate the parameter of interest Q with a given coordinate P with an instant corresponding to the coordinate P of the vehicle 3 by interpolation in the spatial domain of the function representative of the values ​​of the parameter of interest Q measured as a function of the coordinate P and of the function representative of the values ​​of the coordinate P of the vehicle 3 measured as a function of time.

[0213] According to this same variant, the first step 110 of the method 100 is then a step of measuring the parameter of interest Q of a radio link between the vehicle and the ground equipment 40 as a function of the coordinate of the vehicle.

[0214] According to another variant, the parameter of interest Q of the radio link is a power level in reception of a radio signal received by the ground equipment 40 and transmitted by the vehicle 3 via the corresponding radio link.

[0215] Each radio transceiver unit 42 of the ground equipment 40 then comprises a device for measuring the power level in reception of radio signals received by the antenna 44 of the unit 42.

[0216] The memory 56 of the ground station 50 then comprises a module for measuring the parameter of interest Q of the radio link between the ground equipment 40 and the vehicle 3, as a function of time, similar to the module 28 of the communication device 12 of the vehicle 3 described above.

[0217] According to this same variant, the first step 1 10 is then carried out by the module for measuring the parameter of interest Q of the ground station 50.

[0218] According to another variant, the useful radio link between the vehicle 3 and the ground station 50 is used to communicate data other than those representing the signaling. For example, the useful radio link is used to transmit to the ground station 50 a remote surveillance video stream, or to provide a connection allowing the passengers of the vehicle 3 to connect to the internet via a Wi-Fi network on board the vehicle 3. The invention applies in the same way: it makes it possible to characterize the vehicle-ground radio link. The location data can be obtained differently (for example via the location information sent by the vehicle 3 for signaling purposes or via an existing GPS on board the vehicle 3). According to another variant, the location data are not available and the curves of the parameter Q of interest are a function of time and no longer of position. They are analyzed by subtracting from each curve of interest its start time.If all vehicle passages are at equal speeds, the curves can be analyzed jointly, otherwise a transformation of the curves allows comparison.

[0219] According to yet another variant, the memory 24 of the vehicle 3 further comprises a storage module 34 configured to store the groups of measurement data of the parameter of interest Q and the groups of measurement data of the coordinate P. The radio link management module 32 is then configured to control the radio transceiver unit 16 of the vehicle 3 so that the latter transmits the groups of measurement data of the coordinate P and the groups of measurement data of the parameter of interest Q stored in the storage module 34 to the ground equipment 40 with which the vehicle 3 is paired.

[0220] The module 34 is for example a software module comprising software code instructions recordable on a memory and executable by a processor. Alternatively, the module 34 is provided in the form of a programmable logic component or a dedicated integrated circuit.

[0221] The memory 24 comprises, for example, the module 34 in the form of a software module capable of being executed by the processor 22.

[0222] Thanks to the invention, the quality of the radio links between the vehicle and the ground equipment is evaluated on the basis of the analysis of the radio links actually connecting the vehicle and the ground equipment. The evaluated quality of the radio links is therefore precise since it is deduced from real radio links.

[0223] Furthermore, these measurements can be made both in the network testing phases before regular service and during it. In the latter case, it will be measured in real operating conditions, being able, for example, to detect the impact of two vehicles crossing, one masking the radio network for the other, whereas this is generally not tested in the network development phase. Finally, and most importantly, it is almost no longer necessary to carry out ad hoc investigations when problems arise: it is enough to look at the results of recent processing.

[0224] Furthermore, the characterization of radio links is a function of measurements of the parameter of interest carried out by default by the vehicle or by the ground station for cellular transfer between the different ground equipment. The characterization of radio links is therefore effective insofar as it does not require specific measurements aimed at evaluating the quality of the radio links. Thanks to the invention, the characterization of the quality of radio links makes it possible to detect problems, to make a diagnosis and a prognosis. The invention makes it possible to carry out these tasks automatically and permanently using, for example, so-called machine learning techniques. The invention can be summarized as the comparison of characteristic curves possibly enriched with other relevant indicators. Machine learning algorithms naturally lend themselves to automatically carrying out this type of analysis. The invention describes an example thereof which is not limiting.The invention therefore makes it possible to automate tasks normally carried out by experts.

[0225] The invention also allows for predictive maintenance: by detecting and identifying problems precisely and following their evolution over time, it allows targeted predictive maintenance actions to be launched with sufficient advance notice to be able to do this, for example, at the most advantageous time slots.

Claims

CLAIMS 1. Method (100) for characterizing the quality of a radio link between a vehicle (3), in particular a railway vehicle, moving along a predefined route and at least one piece of ground equipment (40), the position of the vehicle (3) along the predefined route being characterized at each instant by a coordinate (P) along this predefined route, the vehicle (3) and the at least one piece of ground equipment (40) exchanging radio signals via the radio link, the method (100) comprising the following steps: - measurement (110) of a parameter of interest (Q) of the radio link between the vehicle (3) and the at least one piece of ground equipment (40) as a function of time or as a function of the coordinate (P) of the vehicle (3), the parameter of interest (Q) being representative of a quality of the radio link between the vehicle (3) and the at least one piece of ground equipment (40); - measurement (120) of the coordinate (P) of the vehicle (3) as a function of time; - calculation (130) of a reading (REL) of the parameter of interest (Q) as a function of the coordinate (P) of the vehicle (3) from the measurement of the parameter of interest (Q) and the measurement of the coordinate (P); - calculation (140) of a reference curve (REF) of the parameter of interest (Q) of a reference radio link between the vehicle (3) and the at least one piece of ground equipment (40) as a function of the coordinate (P) of the vehicle (3), the reference curve (REF) being representative of an optimal radio signal exchange between the vehicle (3) and the at least one piece of ground equipment (40) via the reference radio link; and - characterization (150) of the quality of the radio link between the vehicle (3) and the at least one piece of ground equipment (40) by comparing the reading (REL) of the parameter of interest (Q) with the reference curve (REF) of the parameter of interest (Q).

2. Method (100) according to claim 1, in which the vehicle (3) is connected with one of the ground equipment (40) via a useful radio link for communicating with a ground station (50), the measurement of the parameter of interest (Q) being carried out to be taken into account for determining the ground equipment (40) with which the vehicle (3) is connected via the useful radio link.

3. Method (100) according to claim 2, wherein the measurement of the coordinate (P) of the vehicle (3) is carried out by the vehicle (3) to receive an authorization for the vehicle (3) to progress on the predefined route issued by the ground station (50).

4. Method (100) according to any one of claims 1 to 3, in which the characterization of the quality of the radio link between the vehicle (3) and the at least one ground equipment (40) comprises a calculation of at least one quality indicator of the radio link, the at least one quality indicator being a variable having a value representative of a satisfactory quality of the radio link or a value representative of a degraded quality of the radio link.

5. Method (100) according to claim 4, wherein when the value of the at least one quality indicator is representative of a degraded quality of the radio link, the characterization (150) of the quality of the radio link further comprises a determination of a cause of the degradation of the radio link.

6. Method (100) according to claim 5, in which the determination of the cause of the degradation of the radio link comprises a comparison of the reading (REL) of the parameter of interest (Q) with typical curves of the parameter of interest (Q) corresponding to different causes of degradation.

7. Method (100) according to any one of claims 4 to 6, in which when the value of the at least one quality indicator is representative of satisfactory quality but tends over time towards a value representative of degraded quality, the characterization (150) of the quality of the radio link further comprises a determination of a duration at the end of which the value of the quality indicator will be representative of degraded quality.

8. Method (100) according to any one of claims 4 to 7, in which the calculation of a first quality indicator comprises a comparison of a decomposition of the reading (REL) of the parameter of interest (Q) into components calculated by principal component analysis and a decomposition of the reference curve (REF) of the parameter of interest (Q) into components calculated by principal component analysis.

9. Method (100) according to claim 8, wherein the at least one ground equipment (40) comprises a first radio transceiver unit (42) and a second radio transceiver unit (42), the radio link comprising a first channel connecting the first radio transceiver unit (42) and the vehicle (3) and a second channel connecting the second radio transceiver unit (42) and the vehicle (3), the calculation of the first quality indicator comprising a comparison of the reading (REL) of the parameter of interest (Q) corresponding to the first channel of the radio link with the reading (REL) of the parameter of interest (Q) corresponding to the second channel of the radio link.

10. Method (100) according to any one of claims 4 to 9, in which the calculation of at least one second quality indicator is a function of the time taken to make a cellular transfer, packet losses, measured flow rates, latencies and / or the speed of the vehicle.

11. Method (100) according to any one of the preceding claims, wherein, when the method comprises a step of measuring (110) the parameter of interest (Q) of the radio link between the vehicle (3) and the at least one ground equipment (40) as a function of time, the calculation (130) of the reading (REL) of the parameter of interest (Q) comprises a synchronization of the function representative of the values ​​of the parameter of interest (Q) measured as a function of time and the function representative of the values ​​of the coordinate (P) of the vehicle (3) as a function of time by associating the longest plateau, or respectively a plurality of consecutive plateaus of the function representative of the values ​​of the coordinate (P) of the vehicle (3) as a function of time with the longest portion, or respectively a plurality of portions, of the representative function of the values ​​of the parameter of interest (Q) measured as a function of time for which, or respectively which, the variance of the value of the parameter of interest (Q) is minimal.

12. Method (100) according to any one of the preceding claims, wherein: - when the method comprises a step of measuring (110) the parameter of interest (Q) of the radio link between the vehicle (3) and the at least one ground equipment (40) as a function of time, the calculation (130) of the reading (REL) of the parameter of interest (Q) comprises the association of the parameter of interest (Q) at a given instant with the coordinate (P) of the vehicle (3) at the given instant by interpolation in the time domain of the function representative of the values ​​of the parameter of interest (Q) measured as a function of time and the function representative of the values ​​of the coordinate (P) of the vehicle (3) measured as a function of time; and - when the method comprises a step of measuring (110) the parameter of interest (Q) of the radio link between the vehicle (3) and the at least one piece of ground equipment (40) as a function of the coordinate (P) of the vehicle, the calculation (130) of the reading (REL) of the parameter of interest (Q) comprises the association of the parameter of interest (Q) with a given coordinate (P) with an instant corresponding to the coordinate (P) of the vehicle (3) by interpolation in the domain spatial function of the representative function of the values ​​of the parameter of interest (Q) measured as a function of the coordinate (P) and of the representative function of the values ​​of the coordinate (P) of the vehicle (3) measured as a function of time.

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