FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
“METHOD FOR CHARACTERIZING THE QUALITY OF A
RADIO LINK BETWEEN A VEHICLE AND A GROUND UNIT”
ALSTOM HOLDINGS of 48 rue Albert Dhalenne 93400 ST OUEN
SUR SEINE, FR;
The following specification particularly describes the invention and the
manner in which it is to be performed.
2
METHOD FOR CHARACTERIZING THE QUALITY OF A RADIO LINK
BETWEEN A VEHICLE AND A GROUND UNIT
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 a5
predefined route and at least one piece of ground equipment.
While moving along its route, a railway vehicle must be in constant radio
communication with servers or IT equipment on the ground via radio equipment on
the ground and on the train. This radio communication, if conducted for signaling
purposes, allows the vehicle to regularly transmit equipment information10
representative of its position along the route to the ground servers/computer, and to
regularly receive in return authorizations to progress on the route from the ground
servers/computer equipment. Authorizations to progress are generated by ground-
based servers/computer equipment and depend at least in part on the coordinate of
the vehicle along the route.15
When the vehicle does not receive within a certain period of time any
authorization to progress, the vehicle stops moving along the route by applying a
procedure known as emergency braking. Such an emergency braking procedure
disrupts traffic and in certain rare cases (long immobilization) can put the vehicle
and its occupants at risk.20
The lack of authorization to progress may result from a deliberate failure to
generate an authorization from ground servers/IT equipment, for example when the
vehicle position along the route requires a the vehicle movement to stop, or from a
degradation of the radio links between the vehicle and ground equipment, making
it impossible to transfer information representative of the vehicle position and/or25
authorizations to progress.
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 when new obstacles appear or when30
interference phenomena occur.
3
It is significantly complex to detect or anticipate degradations of radio links
between the vehicle and ground equipment because they are generally not due to
malfunctions or obvious phenomena.
Currently, it is common practice, initially, to detect severe degradations of
radio links, these severe degradations leading in particular to unwanted emergency5
braking procedures, then, in a second stage, to carry out specific radio measurement
campaigns aimed at precisely detecting the degradations and at diagnosing them.
These radio measurement campaigns are then carried out outside of service
hours during designated time slots, using tools specifically designed for these tasks.
However, the monitoring and diagnostic of degradations is then carried out10
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 already suspected degradations.
One of the aims of the invention is to overcome these drawbacks by
providing a method for monitoring the integrity of the radio links between the15
vehicle and the pieces of ground equipment in an efficient and precise manner.
To this end, 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, the position of
the vehicle along the predefined route being characterized at each time point by a20
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:
- measuring 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 of25
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;
- measuring the coordinate of the vehicle as a function of time;
4
- calculating a reading of the parameter of interest as a function of the
coordinate of the vehicle from the measurement of the parameter of interest and the
measurement of the coordinate;
- calculating 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 a5
function of the coordinate of the vehicle; and
- characterizing the quality of the radio link between the vehicle and the 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 radio10
link between the vehicle and ground equipment directly using measurements of one
or more parameter(s) of interest and coordinates relating to said vehicle.
Characterizing the quality of the radio link is therefore based on an analysis
of the radio link actually connecting the vehicle and the piece of ground equipment.
According to optional features of the characterization method, taken in15
isolation or in any technically feasible combination:
- the vehicle is connected with one of the pieces of ground equipment via a
radio link useful for communicating with a ground station, measuring the parameter
of interest being carried out to be taken into account for determining the piece of
ground equipment with which the vehicle is connected via the useful radio link;20
- measuring the coordinate of the vehicle is carried out by the vehicle to
receive an authorization for the vehicle to progress on the predefined route emitted
by the ground station;
- characterizing the quality of the radio link between the vehicle and the at
least one piece of ground equipment comprises calculating at least one radio link25
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;
- when the value of the at least one quality indicator is representative of a
degraded quality of the radio link, characterizing the quality of the radio link further30
comprises determining a cause of the degradation of the radio link;
5
- determining the cause of the degradation of the radio link includes
comparing the reading of the parameter of interest with typical curves of the
parameter of interest corresponding to different degradation causes;
- when the value of the at least one quality indicator is representative of
satisfactory quality but tends over time towards a value representative of degraded5
quality, characterizing the quality of the radio link further comprises determining a
duration after which the value of the quality indicator will be representative of
degraded quality;
- calculating a first quality indicator includes comparing a breakdown of the
reading of the parameter of interest into components calculated by principal10
component analysis and a breakdown of the reference curve of the parameter of
interest into components calculated by principal component analysis;
- the at least one piece of ground equipment comprises a first radio
transceiver unit and a second radio transceiver unit, the radio link comprising a first
channel connecting the first radio transceiver unit and the vehicle and a second15
channel connecting the second radio transceiver unit and the vehicle, wherein
calculating the first quality indicator comprises comparing 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;20
- calculating at least a second quality indicator is a function of the time taken
to make a handover, packet losses, measured throughputs, latencies and/or vehicle
speed;
- characterizing the quality of the radio link between the vehicle and the at
least one piece of ground equipment further includes taking into account additional25
analysis data;
- 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, calculating the reading of the parameter of interest comprises
synchronizing the function representative of the values of the parameter of interest30
measured as a function of time and the function representative of the values of the
6
coordinate of the vehicle 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 of the vehicle as a function of time with the longest portion,
or respectively a plurality of portions, of the function representative of the values
of the parameter of interest measured as a function of time for which the variance5
of the value of the parameter of interest is minimal; and
- 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, calculating the reading of the parameter of interest comprises
associating the parameter of interest at the given time point with the coordinate of10
the vehicle at the given time point by interpolation in the time domain of the
function representative of the values of the parameter of interest measured as a
function of time and of the function representative of the values of the coordinate
of the vehicle measured as a function of time; and
- when the method comprises a step of measuring the parameter of interest15
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, calculating the reading of the
parameter of interest comprises associating the parameter of interest with a given
coordinate with a time point corresponding to the coordinate of the vehicle by
interpolation in the spatial domain of the function representative of the values of20
the parameter of interest measured as a function of the coordinate and of the
function representative of the values of the coordinate of the vehicle measured as a
function of time.
Other aspects and advantages of the invention will appear upon reading the
following description, given solely by way of non-limiting example and made with25
reference to the appended drawings, in which:
[Fig 1] Fig. 1 is a schematic representation illustrating an assembly
comprising a vehicle, two ground radio equipments and a ground station, the
assembly being suitable for executing the method for characterizing the radio link
between the vehicle and at least one ground radio equipment according to the30
invention;
7
[Fig 2] Fig. 2 is a detailed schematic representation illustrating the assembly
of Fig. 1;
[Fig 3] Fig. 3 is a graph having the parameter of interest as the ordinate and
the coordinate of the vehicle as the abscissa, on which a reading of the parameter
of interest of the radio link between the vehicle and ground equipment as a function5
of the coordinate of the vehicle, resulting from a first pass of the vehicle near the
piece of ground equipment, a reading of the parameter of interest of the radio link
between the vehicle and the piece of ground equipment as a function of the
coordinate of the vehicle, resulting from a second pass of the vehicle near the piece
of ground equipment, and a reference curve of the parameter of interest of a10
reference radio link between the vehicle and the piece of ground equipment as a
function of the coordinate of the vehicle are superimposed;
[Fig 4] Fig. 4 is a schematic representation of a flowchart representing the
method for characterizing the quality of the radio link.
Referring to Figures 1 and 2, an assembly 1 comprises a vehicle 3 configured15
to move along a predefined route, at least one ground equipment 40 arranged along
the predefined route and a ground station 50.
The vehicle 3 is for example a guided land vehicle, in particular a railway
vehicle. In this case, the predefined route is defined along a railway track (not
shown).20
The position of the vehicle 3 on the route is characterized at each time point
by a coordinate P along this route.
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.
According to the example described in the present application, the assembly25
1 comprises a plurality of ground equipment 40 pieces distributed along the
predefined route. Each piece of ground equipment 40 is connected to the ground
station 50.
The vehicle 3 is able to be connected with at least one piece of ground
equipment 40 by a radio link. In particular, the vehicle 3 is able to exchange radio30
8
signals with the piece of ground equipment 40 with which it is connected via the
radio link.
Hereinafter, 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.5
The piece of 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.
The piece of ground equipment 40 in particular comprises at least one radio
transceiver unit 42.
The radio transceiver unit 42 comprises a transceiver 43 and at least one10
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”).
As will be detailed below, for the sake of redundancy, the piece of ground
equipment 40 preferably comprises at least two radio transceiver units 42, in15
particular exactly two radio transceiver units 42. This is an example of a redundant
configuration. There may be other configurations allowing redundancy, for
example, by redundant radio coverage by deploying twice as many pieces of ground
equipment 40.
For example, for the sake of complete redundancy, the pieces of ground20
equipment 40 are grouped in pairs, the pieces of ground equipment 40 of the same
pair being located substantially at the same location along the route. In particular,
the pieces of ground equipment 40 of a same pair provides substantially identical
radio coverage. In other words, in a nominal operating case, the radio links between
the vehicle 3 and each piece of ground equipment 40 of a same pair are substantially25
identical.
The vehicle 3 is configured to continuously communicate with the ground
station 50 via at least one piece of ground equipment 40 among the plurality of
ground equipment 40 pieces. The vehicle 3 is in particular configured to be
connected with said at least one piece of ground equipment 40 via a radio link useful30
for communicating with the ground station 50.
9
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 pieces, in particular via a secondary radio link.
When a piece of ground equipment 40 comprises two radio transceiver units
42, the radio link between the vehicle 3 and said piece of ground equipment 405
comprises a first channel connecting a first radio transceiver unit 42 of said piece
of ground equipment 40 and the vehicle 3 and a second channel connecting a second
radio transceiver unit 42 of said piece of 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.10
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.
The authorization to progress is in particular generated by the ground station
50 as a function of the coordinate P of the vehicle 3, and, for example, in addition15
of coordinates of other vehicles present on the predefined route, of a movement plan
of the vehicle 3 on the route, etc.
When vehicle 3 does not receive any authorization to proceed, it stops its
movement along the predefined route.
In order for the vehicle 3 to be able to move along the predefined route in20
good conditions, it is therefore necessary that communication between the vehicle
3 and the ground station 50 is permanently ensured.
When the vehicle 3 communicates with the ground station 50 via a piece of
ground equipment 40, the vehicle 3 is said to be paired with said piece of ground
equipment 40.25
By "communicating with the ground station" is meant that the vehicle 3 and
the ground station 50 exchange the coordinate of the vehicle P and any authorization
to progress by exchanging radio signals between the vehicle 3 and the piece of
ground equipment 40 with which the vehicle 3 is paired. In other words, the
coordinate of the vehicle P and any authorization to progress are exchanged via the30
10
useful radio link between the vehicle 3 and the piece of ground equipment 40 with
which the vehicle 3 is paired.
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 piece of ground equipment 40 with which the vehicle 3 is paired is degraded, or5
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 piece of ground
equipment 40 allowing to exchange the coordinate P and any authorization to
progress on the predefined route. This operation is called a handover. By "nominal
operation" is meant that there is no particular phenomenon causing abnormal10
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 piece of 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 can15
become a useful radio link as a replacement. This operation is also called a
handover. Pairing the vehicle 3 with other pieces of ground equipment 40 then
makes it possible to ensure a continuous exchange of the coordinate of the vehicle
P and any authorization to progress between the vehicle 3 and the ground station
50, and therefore to ensure the smoothest possible progress of the vehicle 3 on the20
predefined route.
Each radio link between the vehicle 3 and a piece of 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 the25
corresponding piece of ground equipment 40.
For example, the parameter of interest Q is the reception power level of a
radio signal received by the vehicle 3 and transmitted from a piece of ground radio
equipment 40 via the corresponding radio link, in particular the corresponding
channel.30
11
The parameter of interest Q is advantageously taken into account for
conducting the handover between the vehicle 3 and the various pieces of ground
equipment 40.
In the following, as illustrated in the example of Fig. 1, it is considered that
the vehicle 3 is configured, at a given time point during its movement along the5
route, to be connected with a first piece of 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 piece of 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 pieces of ground equipment 40 at the same time.10
According to the example illustrated in Fig. 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 through which the vehicle 3 communicates with the ground station
50 and the second channel C2 is a secondary channel.
As illustrated in Fig. 2, the vehicle 3 comprises a location device 10 and a15
radio signal communication device 12, connected to the location device 10.
The location device 10 is configured to generate location data which are
representative of the coordinate P of the vehicle 3. For example, the location device
10 is a GPS signal receiver or a detection system for detecting ground beacons
whose locations are known and between which a wheel rotation and slip20
measurement system makes it possible to determine the location of the vehicle 3 by
interpolation.
The communication device 12 is able to be connected with the first and
second pieces of ground equipment 40 by the respective radio links L1, L2.
Furthermore, the communication device 12 is configured for25
communicating with the ground station 50 via the first piece of ground equipment
40, in particular via the useful radio link L1, in particular via the useful channel C1,
with the first piece of ground equipment 40.
The communication device 12 comprises a radio transceiver unit 16 and a
central unit 18 connected to the radio transceiver unit 16.30
12
The radio transceiver unit 16 is configured to exchange radio signals with
the first and second pieces of ground equipment 40, in particular with the radio
transceiver unit(s) 42 of the pieces of ground equipment 40, via the respective radio
links L1, L2.
As illustrated in Fig. 1, the radio transceiver unit 16 of the communication5
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. In a non
illustrated alternative, the vehicle 3 comprises two radio transceiver units 16.10
Advantageously, the radio transmission-reception unit 16 further comprises
a measuring device for measuring the reception power level of radio signals
received by the antenna 20 of the unit 16. The measuring device for measuring the
reception power level of the received radio signals is in particular configured to
generate power level measurement data.15
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 piece of ground20
equipment 40. The identifier makes it possible to identify which piece of equipment
on board a vehicle carried out measurement.
The communication device 12 is configured to transmit, among other things,
to the piece of ground equipment 40 with which the vehicle 3 is paired, i.e., the first
piece of ground equipment 40:25
- the measurements 3 of the coordinate P of the vehicle 3; and
- the measurements of the parameter of interest Q of the radio link between
the vehicle 3 and a piece of ground equipment 40, herein the first and/or the second
piece of ground equipment 40.
More generally, the operating mode of a mobile radio system involves30
permanently measuring (at more or less close intervals) all the channels from which
13
a ground station is likely to transmit. The measurements can therefore concern a
plurality of pieces of ground equipment. The communication device 12 on the
vehicle can choose to connect to the piece of ground equipment having the best
signal. The measurements of the parameter of interest can therefore concern a
plurality of pieces of ground equipment which are associated with each5
measurement by a unique identifier assigned thereto.
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.
The communication device 12 is further configured to receive from the piece10
of ground equipment 40 with which the vehicle 3 is paired, i.e. the first piece of
ground equipment 40, any authorization to progress generated by the ground station
50.
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 more15
pieces of ground equipment 40, herein, for example, the first and/or the second
piece(s) of 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 radio link management
module 32 for managing the radio links.
Modules 28, 30 and 32 are, for example, software modules comprising20
software code instructions recordable in 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.
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 28,25
30 and 32 provided in the form of software modules suitable for being executed by
the processor 22.
In an alternative, the module 28 is integrated into the transceiver 19 of the
radio transceiver unit 16.
The module 28 is configured to measure the parameter of interest Q of the30
radio link between the vehicle 3 and a piece of ground equipment 40, herein the
14
first and/or the second piece(s) of 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 piece of 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 the5
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 permit handover decisions to be made.
In particular, the module 28 is configured to receive the power level
measurement data from the radio transceiver unit 16, in particular from the10
measuring device for measuring the reception power level of the radio signals
received by the antenna 20 of the unit 16.
Typically, the measurements of the parameter of interest Q are used to make
pairing change decisions in pairing to a piece of ground equipment 40 depending
on the signal level of the one to which the vehicle 3 is paired. Typically, these15
measurements or a subsampling thereof will be used for the purposes of the
invention. The subsampling is chosen so as to preserve the essential characteristics
of the signal depending on the location.
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 equal20
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 piece of ground
equipment 40, herein the first and/or the second piece(s) of ground equipment 40,
every 20 ms.
Other interesting parameters for assessing radio quality can be measured,25
for example the time taken to perform a handover (change in pairing), packet losses,
the measured throughput, latency (round-trip time of a radio signal between the
vehicle 3 and the piece of ground equipment 40).
As mentioned above, the parameter of interest Q of the radio link is taken
into account to determine a possible change in pairing between the vehicle 3 and30
the piece of ground equipment 40 (handover).
15
For example, if the parameter of interest Q of the useful radio link is
representative of an unsatisfactory signal for exchanging the coordinate P of the
vehicle 3 and any authorization to progress, the vehicle 3 is paired, where
applicable, with another piece of ground equipment 40 for which the parameter of
interest Q of the radio link is representative of a satisfactory signal for said5
exchange.
In a particular example, if the reception power level of a radio signal
exchanged by the useful radio link is lower than a predetermined threshold, the
vehicle 3 subsequently communicates, where applicable, with the ground station 50
via another piece of ground equipment 40, thus via another radio link, in particular10
for which the reception power level of radio signals exchanged by the other radio
link is higher than the predetermined threshold.
For example, 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:15
- an identifier of the involved piece of ground equipment 40, in particular of
the radio transceiver unit 42 of the involved piece of ground equipment 40;
- the value of the measured parameter of interest Q; and
- the time point at which measuring the parameter of interest Q was carried
out.20
The module 30 is configured to receive the location data from the location
device 10.
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 time25
interval is for example between 400 ms and 800 ms, in particular substantially equal
to 600 ms. Thus, for example, module 30 is configured to measure the coordinate P
of vehicle 3 every 600 ms.
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,30
each group of measurement data of the coordinate P comprising:
16
- a rank number of the measurement relative to the order of all the carried
out measurements of the coordinate P;
- the value of the measured coordinate P;
- the time point at which measuring the coordinate P was carried out.
Advantageously, each group of measurement data of the coordinate P5
further comprises:
- the speed of vehicle 3; and
- the direction of movement of the vehicle 3.
Advantageously, the radio link management module 32 is suitable for
changing the piece of ground equipment 40 with which the vehicle 3 is paired, in10
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.
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 is15
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
piece of ground equipment 40 and is paired with the second piece of ground
equipment 40.
The radio link management module 32 is further configured to control the20
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 piece of 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 groups25
of measurement data of the parameter of interest Q to the piece of ground equipment
40 with which the vehicle 3 is paired, in other words via the useful radio link, for
example, in real time. Alternatively, this data is, for example, stored on board the
vehicle 3 and transmitted later.
For example, the radio link management module 32 is configured to control30
the radio transceiver unit 16 of the vehicle 3 so that the latter transmits the data
17
groups of the parameter of interest Q successively determined with the first time
interval between the determinations.
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 coordinate P of the vehicle 3 as a function of time, to each radio transceiver5
unit 42 of the piece of 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 coordinate P to the piece of ground equipment 40 with
which the vehicle 3 is paired.10
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 successively transmits
the groups of measurement data of the coordinate P at second regular time intervals.
Each piece of ground equipment 40 is uniquely associated with an identifier.
As explained above, this identifier is used by the module 28 of the communication15
device 12 of the vehicle 3 to generate any measurement data group of the parameter
of interest Q of any radio link between the vehicle 3 and the piece of ground
equipment 40 associated with said identifier.
For example, the unique identifier of the radio transceiver unit 16 is
transmitted with the measurements and makes it possible to match these20
measurements with the vehicle 3 and in particular the module 28.
As mentioned above, each piece of ground equipment 40 comprises at least
one radio transceiver unit 42 with which the vehicle 3 is intended to exchange radio
signals.
Advantageously, each piece of ground equipment 40 comprises at least two25
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 in the same place. According to a
particular example, each piece of ground equipment 40 comprises exactly two units
42.30
18
Advantageously, each radio transceiver unit 42 of each piece of ground
equipment 40 is uniquely associated with an identifier. This identifier is in particular
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 said5
identifier. The identifier of the radio transceiver unit 42 is used to identify which
piece of ground equipment has transmitted the signal being measured.
Each radio transceiver unit 42 of the same piece of 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 3,10
emitted by the radio transceiver unit 16 of the vehicle 3.
Each piece of 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 50.15
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 to progress on the route. Alternatively, the ground station 5020
comprises an internet access server configured to provide internet access to
passengers located in the vehicle 3. According to another alternative, the ground
station 50 comprises a security server able to process security-related data (video
surveillance images, passenger information) generated or processed by dedicated
pieces of equipment on board the vehicle 3.25
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 data and conduct its processing.
In one implementation, the ground station 50 comprises a characterization
assembly 52 configured for characterizing the quality of the radio link between the30
19
vehicle 3 and the piece of ground equipment 40, herein the first and/or second
piece(s) of 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 reference5
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.
Advantageously, the characterization assembly 52 further comprises a
database 66 grouping together data relating to the vehicle 3 and to the pieces of10
ground equipment 40 and a preparation module 68 for preparing the data relating to
the vehicle 3 and to the pieces of ground equipment 40.
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.15
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.
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 the20
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.
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 storage25
module 60, in particular from the values of the measured parameter of interest Q
and the time points 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 storage30
20
module 60, in particular from the values of the measured coordinate P and the time
points at which the measurements of the coordinate P were carried out.
Advantageously, the module 62 is further configured to synchronize the
function representative of the values of the parameter of interest Q as a function of
time and the function representative of the values of the coordinate P of the vehicle5
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. Ex-post
synchronizing the captured data then allows them to be processed jointly.
In particular, the module 62 is configured to synchronize the functions by10
associating the longest plateau of the function representative of the values of the
coordinate P of the vehicle as a function of time with the longest portion 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, this plateau is representative of a long stop of vehicle 3.15
According to an alternative, 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 of the vehicle P 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 the20
value of the parameter of interest Q is minimal. In particular, these plateaus are
representative of successive stops of the vehicle 3.
Still advantageously, the module 62 is configured to associate the parameter
of interest Q at a given time point with the coordinate P of the vehicle 3 at the given
time point by interpolation in the time domain of the function representative of the25
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.
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, from30
the functions respectively representative of the values of the parameter of interest
21
Q as a function of time and of the values of the coordinate P of the vehicle 3 as a
function of synchronized time.
While 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 measurements5
makes it possible to know to which piece of ground radio equipment the vehicle
was connected when these messages were received, and what the quality of the link
was.
Two readings REL of the parameter of interest Q as a function of the
coordinate P of the vehicle 3 are illustrated as an example in Fig. 3. The parameter10
of interest Q is expressed in dBm and the coordinate P is expressed in m.
A first reading REL corresponds to the radio link between the vehicle 3 and
piece of ground equipment 40 during a first pass of the vehicle 3 near the piece of
ground equipment 40, and a second reading REL corresponds to the radio link
between the vehicle 3 and the same piece of ground equipment 40 during a second15
pass of the vehicle 3 near the piece of ground equipment 40. Alternatively, the
second reading corresponds to another vehicle passing near the piece of 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, matching several readings obtained by vehicles makes it possible to bring20
out malfunctions in radio equipment on board the vehicle and the other vehicle.
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 a piece
of ground equipment 40, in particular the piece of ground equipment 40 for which
the quality of the radio link is to be characterized, in particular as a function of the25
coordinate P of the vehicle 3.
The reference curve REF is representative of an optimal radio signal
exchange between the vehicle 3 and the piece of ground equipment 40 via the
reference radio link.
For example, the module 64 is configured to calculate the reference curve30
REF from measurements of the parameter of interest Q and measurements of
22
coordinate P taken when the vehicle 3 is traveling in optimal conditions and when
the radio transceiver units 42 of the pieces of ground equipment 40 and the radio
transceiver unit 16 of the vehicle 3 are precisely calibrated.
A reference curve REF is illustrated by way of example in Fig. 3. In Fig. 3,
the reference curve REF substantially corresponds to the reference radio link5
between the vehicle 3 and the ground equipment 40 to which the first and second
illustrated readings REL correspond.
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 40.10
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 pieces of ground equipment 40 (structural
characteristics, settings, etc.), data relating to the positions of the radio transceiver
units 42 of the pieces of ground equipment 40, data relating to the environments15
around the radio transceiver units 42 of the pieces of ground equipment 40
(surrounding environments or nearby transmitting devices influencing signal
propagation) and data relating to the identifiers of the pieces of ground equipment
40, in particular the radio transceiver units 42 of the pieces of ground equipment
40, data relating to the geographical and operational environment (e.g., in the case20
of lengths and structures of the tracks, position of the platforms, size and
configuration of the tunnels, etc.).
The preparation module 68 is configured to format the data contained in the
database 66 so that it can be used by the characterization module 60.
The preparation module 68 is, in particular, configured to generate a25
database prepared from the database 66, the data of which is suitable for being used
by the characterization module 70 to characterize the quality of the radio link.
The characterization module 70 is configured to characterize the quality of
the radio link between the vehicle 3 and the piece of ground equipment 40, by
comparing the reading REL of the parameter of interest Q with the reference curve30
REF of the parameter of interest Q.
23
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.
The characterization module 70 comprises, for example, a submodule 74 for
calculating at least one radio link quality indicator, a diagnostic submodule 76 and5
a prognosis submodule 78.
Advantageously, submodule 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 satisfactory quality of the radio link or a value representative of
degraded quality of the radio link.10
For example, the variable takes a binary value depending on whether the
quality is satisfactory or degraded. In a specific example, when the quality is
satisfactory, the quality indicator is 1 and when the quality is degraded, the quality
indicator is 0. Alternatively, the variable takes a continuous value corresponding to
a “distance” calculated between the reference curve and the reading.15
Still advantageously, submodule 74 is configured to calculate a first quality
indicator. In particular, to calculate the first quality indicator, the submodule
compares a breakdown of the reading REL of the parameter of interest Q into
components calculated by principal component analysis and a breakdown of the
reference curve REF of the parameter of interest Q into components calculated by20
principal component analysis.
In particular, the reading REL of the parameter of interest Q and the
reference curve REF of the parameter of interest Q are respectively broken down
into a linear combination of basis functions. The reading REL of the parameter of
interest Q and the reference curve REF of the parameter of interest Q are then25
characterized by the coefficients of their respective linear combinations. The vector
comprising the coefficients of the linear combination of the 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 are respectively called
reading signature and reference signature.30
24
The submodule 74 is in particular configured to calculate a mathematical
distance between the read signature and the reference signature, in other words
between the vector comprising the coefficients of the linear combination of the
reading REL of the parameter of interest Q and the vector comprising the
coefficients of the linear combination of the reference curve REF of the parameter5
of interest Q. The distance is for example the Minkowski distance.
For example, when the distance between the read signature and the reference
signature is greater than a predetermined distance threshold, submodule 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 than10
the predetermined distance threshold, submodule 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
rate of false positives.
Advantageously, the submodule 74 is configured to compare the reading15
REL of the parameter of interest Q corresponding to the first channel of the radio
link and the reading REL of the parameter of interest Q corresponding to the second
channel of the radio link. Since the radio coverages of the radio transceiver units 42
of the piece of ground equipment 40 are substantially identical, the readings REL
of the parameter of interest Q of the first and second channels of the radio link20
should be identical. A discrepancy between the readings REL of the parameter of
interest Q of the first and second channels indicates a degradation in the quality of
a radio link channel.
Advantageously, the submodule 74 is suitable for recognizing the absence
of a group of measurement data of the coordinate P of the vehicle in the storage25
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 piece of ground equipment 40 with which the vehicle 3 is paired.
In particular, submodule 74 is suitable for recognizing the absence of a
group of measurement data of the coordinate P of the vehicle 3 when the storage30
module 60 of the ground station 50 does not store any group of measurement data
25
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. submodule 74 then recognizes that the n-th
measurement of the coordinate P of vehicle 3 never reached ground station 50.
Similarly, it is possible to detect the absence of several consecutive data groups (for5
example, between n-1 and n+5 representing the loss of 5 consecutive data groups).
Still advantageously, submodule 74 is configured to calculate at least one
other quality indicator, in particular when the submodule 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 messages10
associated with the reading REL when vehicle 3 passes. This indicator will make it
possible to enrich and improve the characterization of the quality of the radio link.
According to a particular example, submodule 74 is furthermore suitable for
associating each value representative of degraded quality of a quality indicator with
a piece of ground equipment 40, in particular with a radio transceiver unit 42 of the15
piece of ground equipment 40, by associating said value of the quality indicator
with the identifier of the piece of ground equipment 40 taken from the group of
measurement data of the parameter of interest Q having led to calculating said value
of the quality indicator. This makes it possible to distinguish the pieces of ground
equipment 40 for which the radio link is degraded.20
Advantageously, the submodule 74 is further configured to calculate other
quality indicators, for example a second quality indicator, as a function of packet
losses, of the measured throughput, of the latency, of 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 effect on the applications which use25
this link.
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 submodule 76 is
configured to determine a degradation cause.30
26
A degradation cause 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 setting of the radio transceiver units 42, an
interference phenomenon, etc.
Advantageously, the diagnostic submodule 76 is suitable for accessing a5
database relating to different radio link degradation causes. The data relating to
different deterioration causes is, for example, obtained by simulation or in real cases
by provoking voluntarily the deterioration cause during tests of the vehicle 3 and/or
of the pieces of ground equipment 40.
The data relating to the different degradation causes include, for example,10
associations between degradation causes and typical curves of the parameter of
interest Q as a function of the coordinate P of the vehicle 3, corresponding to said
degradation causes.
Advantageously, the diagnostic submodule 76 is configured to recognize the
degradation cause of the radio link by comparing the reading REL of the parameter15
of interest Q with the typical curves of the parameter of interest Q corresponding to
the different degradation causes.
For example, the diagnostic submodule 76 is configured to compare a
breakdown of the reading REL of the parameter of interest Q into components
calculated by principal component analysis and the breakdowns of the typical20
curves of the parameter of interest Q corresponding to the different degradation
causes into components calculated by principal component analysis.
Alternatively or optionally, the diagnostic submodule 76 is configured to
determine the degradation cause of the radio link based on the mean value of the
difference between the reading REL of the parameter of interest Q and the reference25
curve REF of the parameter of interest Q.
In particular, when the mean value 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), the30
diagnostic submodule 76 determines that the parameter of interest Q is constantly
27
attenuated along the curve. The diagnostic submodule 76 then determines that the
degradation cause 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 42.5
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.
Alternatively or optionally, the diagnostic submodule 76 is configured to10
determine the degradation cause 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.
Alternatively or optionally, the diagnostic submodule 76 is configured to
determine which physical antenna 44 is degraded in the case where the ground15
transceiver unit 42 comprises two physical antennas 44 each aiming, 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 splitter which splits the signal in two and allows two
radio cables to be connected to each antenna 44. In this case, for example, it can be20
detected that one of the two physical antennas 44 has a problem if only the curve
corresponding thereto is degraded.
Alternatively or optionally, the diagnostic submodule 76 is configured to
detect that the degradation comes from the change in pointing of the antenna
(typically if the antenna has been screwed incorrectly, it will gradually tilt25
downwards). By simulation, the diagnostic submodule 76 can estimate the
deformation that the reference curve REF or the reading REL would undergo for
different tilt angles. By comparing the simulated curve with the observed curve, the
diagnostic submodule can then detect the problem and approximately quantify the
inclination.30
28
Alternatively or optionally, the diagnostic submodule 76 is configured to
detect that the degradation originates from a new obstacle in the radio propagation
path. The reading REL will then be distorted relative to the reference curve REF.
The diagnostic submodule 76 is then able to indicate the most probable deterioration
cause as being a new obstacle by ruling out a possible change in inclination (using5
a simulation or by detecting a constant offset).
Advantageously, the diagnostic submodule 76 is configured to modify the
database relating to the degradation causes by associating a reading REL of the
parameter of interest Q with a degradation cause. For example, if machine learning
algorithms are used for degradation detection and diagnostic, it can be reinforced10
(reinforcement learning) based on this information and automatically improve its
accuracy.
Also advantageously, the diagnostic submodule 76 is configured to
determine the degradation cause, further, on the basis of direct or indirect
interference measurements carried out along the route. Typically, a high level of15
interference, for example less than 10dB above the level of a useful signal, does not
change the reading REL if it is derived from the measurement of the received signal
level. On the other hand, a high level of interference degrades secondary quality
indicators which can be for example simultaneously measured, such as for example
the noise level or signal-to-noise ratio, the radio quality indicator as measured on20
4G networks (RSRQ, meaning “Reference Signal Received Quality”), or
application indicators such as packet loss or reduction in throughput. Additionally
and optionally, interference can be explicitly measured by dedicated radio modules.
The combination of these measurements makes it possible to conclude that there is
interference and to locate it approximately.25
Advantageously, the diagnostic submodule 76 comprises a complete
machine learning processing chain configured to integrate all of the measurements
into its processing to automatically provide accurate diagnoses.
29
Advantageously, the prognosis, therefore the prediction of the temporal
evolution of the degradations, will be carried out by analyzing the temporal
evolution of the indicators linked to the diagnostic.
In particular, when the value of the at least one quality indicator, in particular
the first quality indicator, is representative of satisfactory quality but tends over5
time towards a value representative of a degraded quality of the radio signal
received by the vehicle, the prognosis submodule 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.
Advantageously, the characterization assembly further comprises a report10
establishment module 72 for establishing a report on the quality of the radio links.
The module 72 is configured to record for each radio link between the
vehicle and the radio transceiver units 42 of the piece of ground equipment 40, the
at least one quality indicator calculated by the submodule 74, where applicable the
degradation cause of the corresponding radio link determined by the diagnostic15
submodule 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 submodule 78.
The modules 60, 62, 64, 66, 68, 70 and 72 are for example provided in the
form of software applications recordable in a memory 56 and executable by a20
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.
In an exemplary embodiment, the characterization assembly 52 is integrated
into the ground station 50, which comprises for example a processor 54 and a25
memory 56 containing the software modules 60, 62, 64, 66, 68, 70 and 72 suitable
for being executed by processor 54.
In another exemplary embodiment, the characterization assembly 52 is
virtualized and implemented using the physical resources of one or more piece(s)
of computer equipment, each located in the ground station 50 or remotely.30
30
In the following, with reference to Fig. 4, a characterization method 100 for
characterizing the quality of a radio link between the vehicle 3 and at least one piece
of ground equipment 40 is described.
The vehicle 3 is connected with a first piece of ground equipment 40 via a
radio link useful for communicating with the ground station 50. Measuring the5
parameter of interest Q is carried out on all the pieces of ground equipment 40
whose signal can be received and decoded to be taken into account to determine the
piece of ground equipment 40 with which the vehicle 3 will be connected via the
useful radio link.
For the sake of clarity and conciseness, the vehicle 3 is considered to be10
further connected with a second piece of ground equipment 40 via a secondary radio
link.
The method 100 comprises a first step 110 of measuring the parameter of
interest Q of a radio link between the vehicle and a piece of ground equipment 40,
herein the first or second piece of ground equipment 40, as a function of time.15
Advantageously, the first step 110 is carried out by module 28 of the
communication device 12 of the vehicle 3.
Herein, measuring the parameter of interest Q of the radio link is carried out
by the vehicle 3 to be taken into account to determine the piece ground equipment
40 via which the vehicle 3 communicates with the ground station 50.20
For example, the parameter of interest Q is measured with a constant first
time interval between measurements.
Advantageously, the first step 110 comprises measuring the parameter of
interest Q of the first channel connecting the first radio transceiver unit 42 as a
function of time and measuring the parameter of interest Q of the second channel25
connecting the second radio transceiver unit 42 as a function of time.
The method then comprises a second step 120 of measuring the coordinate
P of the vehicle 3 as a function of time.
For example, the coordinate P of vehicle 3 is measured with a second
constant time interval between measurements.30
31
Advantageously, the second step 120 is carried out by module 30 of the
communication device 12 of the vehicle 3.
Measuring the coordinate P of the vehicle 3 is here carried out by the vehicle
3 to receive an authorization for the vehicle 3 to progress on the predefined route
from the piece of ground equipment 40 with which the vehicle is paired, the5
authorization to progress being emitted 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
piece of ground equipment 40 with which the vehicle 3 is paired, in other words via
the useful radio link.10
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 piece of ground equipment 40 with which the vehicle 3 is paired,
in particular to the ground station 50.
The measurements of the parameters of interest Q as a function of time and15
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.
The method then comprises a third step 130 of calculating the reading REL20
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 from the
measurement of the coordinate P of the vehicle as a function of time.
Advantageously, the third step 130 is carried out by module 62 of the
characterization assembly 52.25
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 time points at which the respective measurements of the parameter of30
interest Q were carried out. In the third step 130, the module 62 further generates a
32
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 62, in particular from the values of the measured coordinate P and
the time points at which the respective measurements of the coordinate P were
carried out.5
For example, the third step 130 comprises synchronizing 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 of the function
representative of the values of the coordinate P of the vehicle 3 as a function of time10
with the longest portion 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 an alternative, the third step 130 comprises synchronizing the function
representative of the values of the parameter of interest Q measured as a function15
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 3 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 the20
variance of the value of the parameter of interest Q is minimal.
Advantageously, the third step 130 further comprises associating the
parameter of interest Q of the radio link at a given time point with the coordinate P
of the vehicle 3 at the given time point by interpolation in the time domain of the
function representative of the values of the parameter of interest Q measured as a25
function of time and of the function representative of the values of coordinate P of
the vehicle 3 as a function of time.
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
62, from the functions respectively representative of the values of the parameter of30
33
interest Q as a function of time and of the synchronized values of the coordinate P
of the vehicle 3 as a function of time.
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 piece of ground equipment 40 as a function of the coordinate5
P of the vehicle 3.
Advantageously, the fourth step 140 is carried out by module 64 of the
characterization assembly 52.
In particular, the module 64 calculates the reference curve REF from
measurements of the parameter of interest Q and measurements of coordinate P10
taken when the vehicle 3 is traveling in optimal conditions and when the radio
transceiver units 42 of the pieces of ground equipment 40 and the radio transceiver
unit 16 of the vehicle 3 are precisely calibrated.
Then, the method comprises a fifth step 150 of characterizing the quality of
the radio link between the vehicle 3 and the piece of ground equipment 40 by15
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 includes
in particular the detection, diagnostic and prognosis of faults affecting the radio
link.
Advantageously, the fifth step is carried out by the characterization module20
70 of the characterization assembly 52.
Even more advantageously, characterizing the quality of the radio link is
carried out by artificial intelligence.
For example, the fifth step 150 comprises a substep of calculating at least
one radio link quality indicator. The substep of calculating the at least one quality25
indicator corresponds in particular to the detection of faults affecting the radio link.
The substep of calculating the at least one quality indicator is
advantageously carried out by the submodule 74 of the characterization module 70
of the characterization assembly 52.
Here, the substep of calculating the at least one quality indicator, in30
particular calculating a first quality indicator includes comparing the breakdown of
34
the reading REL of the parameter of interest Q into components calculated by
principal component analysis and a breakdown of the reference curve REF of the
parameter of interest Q into components calculated by principal component
analysis.
In particular, during the substep of calculating the at least one quality5
indicator, the submodule 74 calculates a mathematical distance between the read
signature and the reference signature, in other words between the vector comprising
the coefficients of the linear combination of the reading 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.10
For example, the substep of calculating the at least one quality indicator, in
particular the first quality indicator, further comprises 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.15
Advantageously, during the fifth step 150, the submodule 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 submodule 74 recognizes the
absence of a group of measurement data of the coordinate P, the submodule 74
calculates another quality indicator and associates with it a value representative of20
degraded quality.
Advantageously, when the value of one or more quality indicator(s) 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 substep of determining a degradation cause of the radio link. The25
substep of determining the degradation cause of the radio link corresponds in
particular to the diagnostic of faults affecting the radio link.
The determination substep is carried out in particular by the diagnostic
submodule 76.
For example, the diagnostic submodule 76 accesses the database relating to30
different degradation causes. The diagnostic submodule 76 recognizes the
35
degradation cause by comparing the reading REL of the parameter of interest Q
with the typical curves of the parameter of interest Q corresponding to the different
degradation causes.
Still advantageously, when the value of the at least one quality indicator, in
particular the first quality indicator, is representative of satisfactory quality but5
tends over time towards a value representative of degraded quality, the fifth step
150 further comprises a substep of determining a duration after which the value of
the quality indicator will be representative of degraded quality. The substep of
determining a duration after which the value of the quality indicator will be
representative of degraded quality corresponds in particular to the prognosis of10
faults affecting the radio link.
For example, the fifth step 150 further comprises calculating at least one
other second quality indicator as a function of the time taken to perform a handover,
packet losses, measured throughputs, latencies and/or speed of the vehicle 3.
For example, the fifth step 150 further comprises taking into account15
additional analysis data provided such as the level of interference, the duration of
the change of radio link (“handover”), the throughput observed on the radio link.
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. In the fifth step 150, characterizing the20
quality of the radio link is then carried out on the basis of the prepared data.
Optionally, during a sixth step 160, the module 72 records for each radio
link between the vehicle and the radio transceiver units 72 of the piece of ground
equipment 42, the at least one quality indicator calculated by the submodule 40,
where applicable the corresponding degradation cause determined by the diagnostic25
submodule 74, 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 submodule 76. The elements stored in the module 72 are able to be
analyzed by an operator to learn about the quality of the radio link between the
vehicle 3 and the piece of ground equipment 40.30
36
The characterization method is implemented by an electronic
characterization device, and in particular the steps of calculating a reading REL,
calculating a reference curve and characterizing the radio link.
Advantageously, the invention described above lends itself to any automated
analysis that machine learning allows.5
According to an alternative, 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.
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 a10
function of the coordinate of the vehicle 3 and the measurements of the coordinate
P of the vehicle 3 as a function of time.
The module 62 is then advantageously configured to associate the parameter
of interest Q with a given coordinate P with an time point corresponding to the
coordinate P of the vehicle 3 by interpolation in the spatial domain of the function15
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.
According to this same alternative, the first step 110 of the method 100 is
then a step of measuring the parameter of interest Q of a radio link between the20
vehicle and the piece of ground equipment 40 as a function of the coordinate of the
vehicle.
According to another alternative, the parameter of interest Q of the radio
link is a reception power level of a radio signal received by the piece of ground
equipment 40 and transmitted by the vehicle 3 via the corresponding radio link.25
Each radio transceiver unit 42 of the pieces of ground equipment 40 then
comprises a measuring device for measuring the reception power level of radio
signals received by the antenna 44 of the unit 42.
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 piece of ground30
37
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.
According to this same alternative, the first step 110 is then carried out by
the module for measuring the parameter of interest Q of the ground station 50.
According to another alternative, the useful radio link between the vehicle5
3 and the ground station 50 is used to communicate data other than that
representative of the signaling. For example, the useful radio link is used to transmit
a remote surveillance video stream to the ground station 50, or to provide a
connection allowing 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 allows10
the vehicle-ground radio link to be characterized. The location data can be obtained
differently (e.g., via location information sent by vehicle 3 for signaling purposes
or via an existing GPS on board vehicle 3).
Alternatively, location data is not available and the curves of the parameter
of interest Q are time-dependent rather than position-dependent. It is analyzed by15
subtracting the starting time point from each curve of interest. If all vehicle passes
are at equal speeds, the curves can be analyzed jointly, otherwise transforming the
curves allows comparison.
According to yet another alternative, the memory 24 of the vehicle 3 further
comprises a storage module 34 configured to store the groups of measurement data20
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 piece of ground25
equipment 40 with which the vehicle 3 is paired.
Module 34 is for example a software module comprising software code
instructions recordable in 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.30
38
The memory 24 comprises, for example, the module 34 in the form of a
software module suitable for being executed by the processor 22.
Thanks to the invention, the quality of the radio links between the vehicle
and the pieces of ground equipment is evaluated on the basis of the analysis of the
radio links actually connecting the vehicle and the pieces of ground equipment. The5
assessed quality of radio links is therefore precise since it is deduced from real radio
links.
Moreover, these measurements can be carried out both during the network
testing phases before regular service and during the latter. In the latter case, it will
be measured in real operating conditions, for example by detecting the effect of two10
vehicles crossing, one hiding the radio network for the other, whereas this is
generally not tested in the network development phase. Lastly, 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.
Furthermore, characterizing the radio links depends on measurements of the15
parameter of interest carried out by default by the vehicle or by the ground station
for the handover between the different pieces of ground equipment. Characterizing
radio links is therefore effective to the extent that it requires no specific
measurement aimed at evaluating the quality of radio links.
Thanks to the invention, characterizing the quality of radio links makes it20
possible to detect problems, their diagnostic and prognoses. The invention makes it
possible to perform these tasks automatically and permanently using, for example,
so-called machine learning techniques. The invention can be summarized as being
a comparison of characteristic curves optionally enhanced with other relevant
indicators. Machine learning algorithms naturally lend themselves to automatically25
conducting this type of analysis. The invention describes a non limiting example.
The invention therefore makes it possible to automate tasks normally carried out by
experts.
The invention also allows for predictive maintenance: by precisely detecting
and identifying problems and following their evolution over time, it allows targeted30
39
predictive maintenance actions to be launched with sufficient advance notice to be
able to do so, for example, at the most advantageous time slots.
40
CLAIMS
1. A 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 time point by a coordinate5
(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, wherein the method
(100) comprises the following steps:
- measuring (110) 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 time10
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);
- measuring (120) the coordinate (P) of the vehicle (3) as a function of time;
- calculating (130) a reading (REL) of the parameter of interest (Q) as a15
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);
- calculating (140) 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 reference20
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
- characterizing (150) 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)25
of the parameter of interest (Q) with the reference curve (REF) of the parameter of
interest (Q).
2. A method (100) according to claim 1, wherein the vehicle (3) is
connected with one of the pieces of ground equipment (40) via a radio link useful30
for communicating with a ground station (50), measuring the parameter of interest
41
(Q) being carried out to be taken into account for determining the piece of ground
equipment (40) with which the vehicle (3) is connected via the useful radio link.
3. A method (100) according to claim 2, wherein measuring the
coordinate (P) of the vehicle (3) is carried out by the vehicle (3) to receive an5
authorization for the vehicle (3) to progress on the predefined route emitted by the
ground station (50).
4. A method (100) according to any one of claims 1 to 3, wherein -
characterizing the quality of the radio link between the vehicle (3) and the at least10
one piece of ground equipment (40) comprises calculating 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.
15
5. A 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, characterizing (150) the quality of the radio link further comprises determining
a cause of the degradation of the radio link.
20
6. A method (100) according to claim 5, wherein determining the
cause of the degradation of the radio link includes comparing the reading (REL) of
the parameter of interest (Q) with typical curves of the parameter of interest (Q)
corresponding to different degradation causes.
25
7. A method (100) according to any one of claims 4 to 6, wherein
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,
characterizing (150) the quality of the radio link further comprises determining a
duration after which the value of the quality indicator will be representative of30
degraded quality.
42
8. A method (100) according to any one of claims 4 to 7, wherein
calculating a first quality indicator includes comparing a breakdown of the reading
(REL) of the parameter of interest (Q) into components calculated by principal
component analysis and a breakdown of the reference curve (REF) of the parameter
of interest (Q) into components calculated by principal component analysis.5
9. A method (100) according to claim 8, wherein the at least one
piece of 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 second10
channel connecting the second radio transceiver unit (42) and the vehicle (3),
wherein calculating the first quality indicator comprises comparing 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.15
10. A method (100) according to any one of claims 4 to 9, wherein
calculating at least a second quality indicator is a function of the time taken to
perform a handover, of packet losses, of measured throughputs, of latencies and/or
of the vehicle speed.20
11. A 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 piece of
ground equipment (40) as a function of time, calculating (130) the reading (REL)25
of the parameter of interest (Q) comprises synchronizing 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 coordinate30
(P) of the vehicle (3) as a function of time with the longest portion, or respectively
a plurality of portions, of the function representative of the values of the parameter
43
of interest (Q) measured as a function of time for which the variance of the value
of the parameter of interest (Q) is minimal.
12. A method (100) according to any one of the preceding claims,
wherein:5
- 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 time, calculating (130) the reading (REL)
of the parameter of interest (Q) comprises associating the parameter of interest (Q)
at the given time point with the coordinate (P) of the vehicle (3) at the given time10
point 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) measured as a
function of time; and
- when the method comprises a step of measuring (110) the parameter of15
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, calculating
(130) the reading (REL) of the parameter of interest (Q) comprises associating the
parameter of interest (Q) with a given coordinate (P) with a time point
corresponding to the coordinate (P) of the vehicle (3) by interpolation in the spatial20
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.