Process for optimizing on-board / ground connectivity for rail transport

Abstract

The invention relates to a method for selecting an access network for implementing a communications link between radio communications equipment (101) on board a railway vehicle (100) and ground-based radio communications equipment (110, 141, 142) when the radio communications equipment (111) on board the railway vehicle is connected to a plurality of access networks (131, 132, 133) enabling it to implement the communications link. It comprises calculating a density score associated with said access networks, and using this density score when making a decision concerning the configuration of the communications link. The invention also relates to radio communications equipment, a system and a computer program for implementing the method for selecting an access network. Figure for abstract: Fig. 1

Description

Title of the invention: Method for optimizing on-board / ground connectivity for rail transport Technical field

[0001] The invention lies in the field of radio communications carried out by a mobile terminal on board a train via different access networks. More specifically, it relates to on-board / ground communications in the context of rail transport. Prior art

[0002] Some on-board railway services involve on-board / ground communications, i.e. communications enabling a device on board the train to be connected to a device outside the train via one or more access networks. These services are, for example, the transmission of data corresponding to voice, video, location information, information relating to control protocols, etc.

[0003] Due to the movement of the train, the on-board mobile terminal(s) must regularly change access network, in order to maintain connectivity with the ground. For certain critical applications, such as telecontrol for example (remote driving), where videos of the train's environment are continuously transmitted to a remote driver, switching between two access networks must be transparent, must not impact the quality of service, and must be done without interruption of connectivity. For this, it is necessary to couple different radio communications technologies that the vehicle is likely to encounter during its journey, and to switch from one to the other during the movement of the vehicle. This is the concept of hybrid communications, in English "adaptable communications".

[0004] One way to ensure continuity of communications is to switch between access networks upon crossing GPS coordinates or kilometer points. Such a method makes it possible to anticipate dead zones and areas of coverage loss, but does not take into account unforeseen events, such as radio problems, bad weather, peaks in resource demand on the access network, etc.

[0005] Another known way to ensure the continuity of communications dynamically consists of switching between access networks according to different criteria relating to the quality of the radio links usable for the hybridization of communications. Among these quality measures, one can find measures reflecting the quality of the radio signal, and / or measures specific to the networks, such as measures bandwidth or latency. These measures can be coupled with a geographic hybridization mechanism.

[0006] However, quality measures have limitations: - radio signal quality measurements do not always reflect the quality of the network link, since it is possible to have good signal quality (SNR, for Signal to Noise Ratio), but little available bandwidth, particularly when the radio cell is congested, - network measurements (bandwidth, latency, etc.) are intrusive measurements that consume network resources. For example, latency measurement requires the transmission of a large data stream over the access network, which consumes radio resources. In addition, these measurements are time-consuming since connection and testing time may be required to obtain the network metrics necessary for decision-making, this connection time being potentially incompatible with the movement of the vehicle.

[0007] The quality measures used by the prior art for the hybridization of communications do not take advantage of the specificity of rail travel, namely precise knowledge of the trajectory of the train (the track), its movement parameters (position, speed, etc.), the number of passengers, and fairly precise knowledge of the number of people around the tracks (in particular in stations, on platforms, in neighboring trains, etc.).

[0008] An object of the invention is therefore to define a method for selecting an access network taking into account the specificities of rail travel to optimize the anticipation of the change in on-board / ground connectivity in a context of multi-technology / multi-operator access networks. Summary of the invention

[0009] To this end, the present invention describes a method for selecting an access network for implementing a communications link between radiocommunications equipment on board a railway vehicle and radiocommunications equipment on the ground. It is carried out when the radiocommunications equipment on board the railway vehicle is connected to a plurality of access networks enabling it to implement the communications link. This method comprises in particular the calculation of a density score associated with the access networks, and the use of this density score when making a decision concerning the configuration of the communications link.

[0010] According to one embodiment, the method for selecting an access network according to the invention comprises: - a first step of determining a density score and comparing this density score with a threshold for each of the available access networks, - a second stage of evaluating the optimal configuration of the communications link taking into account the results of the first stage, - a third stage of configuring the communications link in accordance with the optimal configuration evaluated during the second stage.

[0011] According to one embodiment of the invention, the density score calculated during the first step is used during the second step to select the access networks that can be used to implement said communications link.

[0012] According to an embodiment of the invention compatible with the previous one, the second step comprises adapting the flow rate of said communications link as a function of the density score calculated during the first step.

[0013] Advantageously, the second step further comprises measurements of the quality of radio links on the different access networks.

[0014] According to one embodiment of the invention, the threshold used during the first step depends on the type of access network.

[0015] According to a particular embodiment, the method for selecting an access network according to the invention further comprises a step of verifying the applicability of the optimal configuration evaluated during the second step.

[0016] According to a particular embodiment of the invention, the data exchanged on the communications link are data enabling the remote control of the railway vehicle.

[0017] The invention also relates to radiocommunications equipment intended to be mounted on a railway vehicle. The equipment comprises means for accessing a plurality of access networks and calculation means. The calculation means are configured to implement a method for selecting an access network according to the invention.

[0018] The invention also relates to a system comprising: - radiocommunications equipment, intended to be carried on board a railway vehicle, comprising means of simultaneous access to a plurality of access networks, and - remote calculation means of the radiocommunications equipment.

[0019] The remote calculation means are configured to implement the first and second steps of a method for selecting an access network according to the invention, and to transmit the optimal configuration calculated during the second step to the radiocommunications equipment. The radiocommunications equipment is configured to implement the third step of the method for selecting an access network according to the invention.

[0020] Finally, the invention relates to a computer program product comprising program code instructions for executing the steps of the method for selecting an access network according to the invention. Brief description of the drawings

[0021] The invention will be better understood and other characteristics, details and advantages will appear more clearly on reading the following description, given without limitation, and thanks to the appended figures, given by way of example.

[0022] [Fig. 1] [Fig. 1] represents an example of an operational case in which a method for selecting an access network according to an embodiment of the invention can be implemented.

[0023] [Fig.2] [Fig.2] is a block diagram representing the steps of a process of selecting an access network according to one embodiment of the invention. Description of the embodiments

[0024] [Fig. 1] represents an example of an operational case in which a method for selecting an access network according to an embodiment of the invention can be implemented.

[0025] This method aims to determine the access network to be favored for operating a communications link between a radiocommunications device 101 on board a railway vehicle 100 and one or more remote devices 110 on the ground, i.e. outside the railway vehicle. The remote device may be, for example, a server 111.

[0026] The on-board / ground communications link can for example be used to transmit to the remote server 111 data such as audio data 102, video data 103, signaling data 104 or positioning data 105 acquired from a GNSS receiver (Global Navigation Satellite System). The communications link can also be used in the opposite direction, to transmit various information to the radio communications equipment 101, such as for example commands in the case of remote control.

[0027] The radio communications equipment 101 is configured to allow simultaneous connection to several access networks 131, 132, 133, in order to select the most suitable access network for implementing the communications link with the ground equipment(s) 110.

[0028] The access networks may be any type of access network allowing the on-board radio communications equipment 101 to contact the remote ground equipment 110 directly or indirectly, such as for example one or more public or private MNO (Mobile Network Operator) networks, for example 4G or 5G networks, one or more MVNO (Mobile Virtual Network Operator) networks, one or more Wi-Fi, Bluetooth, etc. terminals located at the edge of the tracks, a satellite link, or any other type of wireless link. The communications link may or may not pass through the internet network 134 or through private networks.The on-board and ground radio communications equipment may include various equipment intended to improve its security, such as for example a firewall 112, and may be configured to implement encrypted communication tunnels.

[0029] The on-board radiocommunications equipment 101 can also be connected to various other equipment through one or more access links, such as for example equipment 141 intended to collect information from sensors arranged on the railways, a server 142 making it possible to obtain information relating to railway stations, a reservation server, a traffic server, etc. If necessary, the on-board radiocommunications equipment 101 can be connected to the remote radiocommunications equipment 110 through a short-range network link such as a Wifi router link 133, itself connected to equipment, such as equipment 142, connected to the ground equipment 110 by a direct link 151, or by a link 152 using for example an internet connection 134.

[0030] The on-board radiocommunications equipment 101 can be connected to one or more access networks allowing it to establish a communications link with the ground radiocommunications equipment 110. It therefore comprises at least one radio antenna, one or more analog transmission and / or reception chains, and calculation means making it possible to carry out the processing necessary to transmit and receive signals on the different access networks, as well as to implement a method for selecting an access network according to the invention.These calculation means may for example be a microprocessor, a DSP (English acronym for Digital Signal Processor), an FPGA (English acronym for Field Programmable Gate Array), an ASIC (English acronym for Application-Specific Integrated Circuit), any combination of these means, or any hardware component making it possible to execute the aforementioned functions.

[0031] The method for selecting an access network from a plurality of access networks according to the invention differs from the state of the art in that it comprises the calculation of a density score associated with the available access networks (131, 132, 133), and the use of this density score when making a decision concerning the configuration of the on-board / ground communications link when several access networks are available, namely the access network to be used and possibly the flow rate.

[0032] [Fig.2] is a block diagram representing the steps of a method for selecting an access network according to an embodiment of the invention when several access networks are available for implementing the communications link between on-board equipment and ground equipment.

[0033] The method comprises a step 201 of measuring a density score associated with each of the available access networks, from different sources of density metrics and occupancy of the collected radio cells. Indeed, for most access networks, the available bandwidth decreases when the number, and therefore the density, of users increases. The technical solution proposed here exploits the determinism of the journey of a train and the possible availability of information specific or not to the railway domain to anticipate reconfigurations of the hybrid communications system. Density score is understood to mean a qualitative value with regard to the density of potential users of the access network.

[0034] The user density associated with an access network is linked to the network occupancy. It can be evaluated by methods specific to access networks, for example specific applications making it possible to make requests to the core network in order to obtain information concerning the number of users of each cell, such as NEF (Network Exposure Function) applications for 5G networks, or their equivalents for 4G networks. In this way, it is possible to determine the occupancy rate of the cell in which the on-board radiocommunications equipment 101 is located, and to deduce therefrom a density score associated with the access network concerned, for example by calculating a density by dividing the bandwidth available for the cell by the number of users and then associating a score with the measured density.

[0035] The user density associated with an access network can also be assessed by methods specific to railway applications, for example: - from on-board CCTV (close-circuit television) information, which allows train occupancy to be assessed. This information can be used to approximate the number of users using available public access networks and to estimate an associated density score, - from CCTV information on the platforms, which allows for the assessment of platform occupancy. Advantageously, a crowd counting solution allows for an accurate count of the number of people on the platforms. It is then possible to estimate a density score associated with the available public access networks, - from station / train occupancy information retrieved from a remote server. For example, it is possible to know quite precisely the number of people on the train and in neighboring trains, from information coming from the ticketing system. It is also possible to know approximately the number of people on the platforms from information provided by access gates to the tracks. It is then possible to estimate a density score associated with the available public access networks.

[0036] The user density associated with an access network can finally be obtained from third-party information, for example shared databases (open Data) providing information on events close to the roads which may impact the user density, such as for example road traffic, the presence of events, etc. It is then possible to deduce a density score associated with the available public access networks.

[0037] All this information makes it possible to establish a density score specific to each type of access network.

[0038] Step 201 of the method for selecting an access network according to the invention then comprises the comparison, for each of the access networks, of the density score with a threshold. The threshold associated with each access network can take into account the specificities of each type of access network: the same user density does not impact a 4G access network in the same way as a Wi-Fi access network. Similarly, for a given user density, a private access network will be less impacted than a public access network. The threshold can also take into account the speeds required for the onboard / ground communications link. It can be established so as to be as homogeneous as possible between the different access networks. The value of the threshold can be established empirically, for example by analyzing the correlation between the number of users, the requested speed and the availability of the network.The threshold should be positioned so that a density score exceeding it indicates that the access network is likely to be congested, and therefore to have a degraded quality of service compared to its nominal quality of service.

[0039] The method for selecting an access network according to the invention then comprises a step 202 of evaluating the optimal configuration of the on-board / ground communications link, taking into account the results of step 201. This step consists of determining the access network, and possibly the flow rates, most suitable for implementing the on-board / ground communications link. It can be implemented in various ways.

[0040] According to one embodiment, the access networks whose density score is higher than the threshold in step 201 are eliminated from a list of access networks that can be used for implementing the on-board / ground communications link. The access network to be used is then chosen from the residual access networks in a manner comparable to what is done in the hybridization networks of the prior art. For example, this choice can be made by comparing the quality of the radio links of the access networks whose density score is lower than the threshold, as a function of the position of the train carrying the on-board radio communications equipment 101, and / or as a function of other considerations such as, for example, considerations on the cost of transmissions.

[0041] Advantageously, when two access networks having density scores lower than the threshold have the same characteristics (same quality of radio link, and / or same cost of use, etc.), the access network to be favored for implementing the on-board / ground communications link is the one having the lowest density score.

[0042] According to one embodiment, the access networks whose density score is greater than the threshold in step 201 are eliminated from a list of access networks that can be used for implementing the on-board / ground communications link, then the choice of the access network to be used is made by planning, from a predetermined list indicating a preferential order of use of the access networks as a function of the geographical position of the on-board radiocommunications equipment 101.

[0043] According to another embodiment, the selected access network is the access network having the smallest density score.

[0044] According to another embodiment, when all the available access networks exceed the density threshold during step 201, the throughput of the communications link is reduced, and the comparison between the density score and the threshold is re-evaluated taking into account this reduction in throughput. The chosen access network can then be selected according to one of the embodiments described previously.

[0045] Reducing the flow rate of the communications link can be done in different ways, such as: - by transmitting only priority services (voice, data, signaling, etc.) over the onboard / ground communications link, - by reducing the quality of certain services, in particular the resolution of video data streams.

[0046] Many other embodiments are possible for this step.

[0047] Finally, the method for selecting an access network according to the invention comprises a step 203 of configuring the on-board / ground communications link in accordance with the access network and transmission parameters (flow rate) determined during the second step 202. This step includes, when necessary, the re-parameterization and reconfiguration of the communications link ensuring on-board / ground connectivity.

[0048] The method for selecting an access network according to the invention can be implemented by the on-board radiocommunications equipment 101, but also by remote equipment, transmitting the configuration calculated during step 202 to the on-board radiocommunications equipment 101 so that it implements step 203 of the method. This equipment can for example be the ground station 111 or any device having calculation means capable of recovering the metrics necessary for implementing the method, of executing steps 201 and 202, and of transmitting the information on the configuration of the on-board / ground communications link to the on-board equipment 101.

[0049] The method may be executed periodically, when passing through defined geographical points, when the quality of the radio link used for on-board / ground communications decreases, and / or when new access networks become available. The device responsible for executing the method may continuously request the information necessary for its implementation, such as density information from the different networks, information on the quality of the radio links, etc.

[0050] A typical application case of the method according to the invention is that of a train entering a busy station. Implementing the method for selecting an access network according to the invention will make it possible to exclude potentially congested public access networks and to direct the communications link towards a private access network or towards satellite communications, which by definition are less likely to be saturated. Conversely, when the train enters a station with little traffic, the selection method according to the invention will direct the communications link towards a public access provider, which may have lower usage costs.

[0051] The method for selecting an access network according to the invention makes it possible to obtain better quality network connectivity than the state-of-the-art methods for on-board / ground communication links, while minimizing the risks of service interruption. It takes advantage of the determinism of railway journeys to define simple and effective criteria for re-evaluating / reconfiguring the on-board / ground connectivity. It makes it possible to anticipate network congestion and availability problems, and to dynamically adapt the hybridization strategy to the surroundings of the on-board radiocommunications equipment. Unlike hybridization based exclusively on network metrics, it can be implemented in a non-intrusive manner. Indeed, the information necessary for calculating density is available from railway operators and radiocommunications operators.

[0052] Advantageously, the method for selecting an access network according to the invention comprises an additional step 204 of verifying the applicability of the optimal configuration of the on-board / ground communications link determined during step 202. This step is prior to step 203 of configuring the on-board / ground communications link.

[0053] It consists of verifying whether the configuration determined during step 202 is compatible with the environment of the on-board radiocommunications equipment 101, for example by verifying that: - the recommended access network is available, - the required flow rate is compatible with the selected access network, - the technology in question is compatible with the speed of the train (so as to avoid, for example, a situation where a train passing through a station without stopping would switch to the station's Wi-Fi network), - the availability time of the selected access network is sufficient with regard to the movement of the railway vehicle, - the radio communications equipment has the necessary authorizations / subscriptions to access the selected access network, - the type of traffic is compatible with the access network technology, for example by prohibiting the transmission of video traffic on links with limited bandwidth, or on links particularly sensitive to congestion, - etc.

[0054] If the optimal configuration is applicable for the radio communications equipment 101, then the method moves on to the next step 203. Otherwise, the method returns to step 202, with the aim of finding another configuration of the on-board / ground communications link.

[0055] The invention relates to the method for selecting an access network described above, but also to: - on-board radiocommunications equipment 101, configured to implement a method for selecting an access network according to one embodiment of the invention, - a system, comprising a calculation means configured to implement steps 201, 202 and possibly 204 of a method for selecting an access network according to the invention, then to transmit the resulting configuration to on-board radiocommunications equipment so that it implements step 203 of the method for selecting an access network, and - a computer program product comprising program code instructions for executing the method when the latter is executed on any computing means.

Claims

Claims

1. Method for selecting an access network for implementing a communications link between radiocommunications equipment (101) on board a railway vehicle (100) and ground-based radiocommunications equipment (110, 141, 142) when the radiocommunications equipment on board the railway vehicle is connected to a plurality of access networks (131, 132, 133) enabling it to implement said communications link, the method being characterized in that it comprises calculating a potential user density score associated with said access networks, and using this potential user density score when making a decision concerning the configuration of said communications link,the method comprising: - a first step (201) of determining a potential user density score and comparing said potential user density score with a threshold for each of the available access networks, - a second step (202) of evaluating the optimal configuration of the communications link using the potential user density score calculated during the first step (201), to select the access networks that can be used to implement said communications link, - a third step (203) of configuring said communications link in accordance with the optimal configuration evaluated during the second step.,

2. A method of selecting an access network according to claim 1, wherein the second step (202) comprises adapting the flow rate of said communications link as a function of the potential user density score calculated during the first step (201).

3. Method for selecting an access network according to one of claims 1 or 2, in which the second step (202) further comprises measurements of the quality of radio links on the different access networks.

4. Method for selecting an access network according to one of claims 1 to 3, in which the threshold used during the first step (201) is a function of the type of access network.

5. Method for selecting an access network according to one of claims 1 to 4, further comprising a step (204) of verifying the applicability of the optimal configuration evaluated during the second step (202).

6. Method for selecting an access network according to one of the preceding claims, in which the data exchanged on the communications link are data enabling remote control of the railway vehicle (100).

7. Radiocommunications equipment (101) intended to be embarked in a railway vehicle (100), comprising means for accessing a plurality of access networks (131, 132, 133), and calculation means, the radiocommunications equipment being characterized in that the calculation means are configured to implement a method for selecting an access network according to one of the preceding claims 1 to 6.

8. System comprising: - radiocommunications equipment (101), intended to be embarked in a railway vehicle (100), comprising means for simultaneous access to a plurality of access networks (131, 132, 133), and - remote calculation means of said radiocommunications equipment (101), characterized in that the remote calculation means are configured to implement the first (201) and the second (202) step of a method for selecting an access network according to one of the preceding claims 1 to 8, and to transmit said optimal configuration calculated during the second step (202) to the radiocommunications equipment (101), and in that the radiocommunications equipment is configured to implement the third step (203) of said method for selecting an access network according to one of the preceding claims 1 to 6.

9. Computer program product comprising program code instructions for executing the steps of the method for selecting an access network according to one of claims 1 to 6 when said computer program is executed on a computing means.

Images