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

Abstract

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

Description

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

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

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

[0003] Due to the train's movement, the onboard mobile terminal(s) must regularly switch access networks to maintain connectivity with the ground. For certain critical applications, such as remote driving, where video of the train's surroundings is continuously transmitted to a remote driver, switching between two access networks must be seamless, must not impact the quality of service, and must occur without any interruption in connectivity. To achieve this, it is necessary to combine different radio communication technologies that the vehicle is likely to encounter during its journey and switch from one to another as the vehicle moves. This is the concept of hybrid communications, also known as "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 process 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, peak demand for resources on the access network, etc.

[0005] Another known way to ensure continuity of communications dynamically is to switch between access networks based on various criteria relating to the quality of the radio links available for hybrid communications. These quality measures may include measures reflecting the quality of the radio signal, and / or network-specific measures, 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 network link quality, as it is possible to have good signal quality (SNR, for Signal-to-Noise Ratio) but little available bandwidth, especially when the radio cell is congested. - Network measurements (bandwidth, latency, etc.) are intrusive and consume network resources. For example, measuring latency requires transmitting a significant data stream over the access network, which consumes radio resources. Furthermore, these measurements are time-consuming, as connection and testing time may be required to obtain the network metrics necessary for decision-making, and this connection time may be incompatible with vehicle movement.

[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 a precise knowledge of the trajectory of the train (the track), of its movement parameters (position, speed, ...), of the number of passengers, and a fairly precise knowledge of the number of people around the tracks (in particular in stations, on platforms, in nearby 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 in order 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 communication link between radio communication equipment installed in a railway vehicle and ground-based radio communication equipment. This method is performed when the radio communication equipment installed in the railway vehicle is connected to a plurality of access networks enabling it to implement the communication link. In particular, this method includes calculating a density score associated with the access networks and using this density score when making a decision regarding the configuration of the communication 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 step to evaluate the optimal configuration of the communication link, taking into account the results of the first step, - a third step of configuring the communication link in accordance with the optimal configuration evaluated during the second step.

[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 usable access networks for implementing said communication link.

[0012] According to an embodiment of the invention compatible with the previous one, the second step includes adapting the throughput of said communication link according to the density score calculated during the first step.

[0013] Advantageously, the second step further includes radio link quality measurements on the different access networks.

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

[0015] According to a particular embodiment, the method of selecting an access network according to the invention further includes 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 communication link are data enabling the remote control of the railway vehicle.

[0017] The invention also relates to radiocommunication equipment intended to be installed in a railway vehicle. The equipment comprises means for accessing a plurality of access networks and computing means. The computing 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: - radiocommunication equipment, intended to be installed in a railway vehicle, comprising means of simultaneous access to a plurality of access networks, and - remote computing means for the radio communications equipment.

[0019] The remote computing 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 radio communications equipment. The radio communications equipment is configured to implement the third step of the method for selecting a network access according to the invention.

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

[0021] The invention will be better understood and other features, details and advantages will become clearer from the following description, given by way of non-limiting reason, and from the accompanying 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 can be implemented according to an embodiment of the invention.

[0023] [Fig.2] Fig.2 is a synoptic diagram representing the steps of a process selection of an access network according to an 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 can be implemented according to an embodiment of the invention.

[0025] This method aims to determine the preferred access network for establishing a communication link between a radio communication device 101 installed in a railway vehicle 100 and one or more remote devices 110 on the ground, i.e., outside the railway vehicle. The remote device could be, for example, a server 111.

[0026] The ship-to-ground communication link can, for example, be used to transmit data such as audio data 102, video data 103, signaling data 104, or positioning data 105 acquired from a GNSS (Global Navigation Satellite System) receiver to the remote server 111. The communication link can also be used in the opposite direction to transmit various information to the radio communication equipment 101, such as 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 to implement the communications link with the ground equipment 110.

[0028] Access networks can be any type of access network allowing the onboard radiocommunication 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, such as 4G or 5G networks, one or more MVNO (Mobile Virtual Network Operator) networks, one or more Wi-Fi, Bluetooth, etc. access points located along the route, a satellite link, or any other type of wireless connection. The communication link may or may not pass through the internet or private networks. Onboard and ground radio communication equipment may include various devices designed to improve security, such as a firewall, and may be configured to implement encrypted communication tunnels.

[0029] The on-board radio communications equipment 101 can also be connected to various other equipment through one or more access links, such as, for example, equipment 141 for collecting information from sensors placed on the railway tracks, a server 142 for obtaining information relating to railway stations, a reservation server, a traffic server, etc. Where appropriate, the on-board radio communications equipment 101 can be connected to the remote radio communications 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 onboard radiocommunication equipment 101 can be connected to one or more access networks enabling it to establish a communications link with the ground radiocommunication equipment 110. It therefore includes at a minimum a radio antenna, one or more analog transmission and / or reception chains, and computing means enabling it 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 computing means can, for example, be a microprocessor, a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), an ASIC (Application-Specific Integrated Circuit), any combination of these means, or any hardware component that can perform the aforementioned functions.

[0031] The method for selecting an access network from among a plurality of access networks according to the invention differs from the prior art in that it includes calculating a density score associated with the available access networks (131, 132, 133), and using this density score when making a decision regarding the configuration of the edge-to-ground communications link when several access networks are available, namely the access network to use and possibly the bandwidth.

[0032] Figure 2 is a synoptic diagram representing the steps of a process of selection of an access network according to an embodiment of the invention when several access networks are available for the implementation of the communication link between on-board equipment and ground equipment.

[0033] The method includes a step 201 of measuring a density score associated with each of the available access networks, based on various sources of density and radio cell occupancy metrics collected. Indeed, for most access networks, the available bandwidth decreases as the number, and therefore the density, of users increases. The technical solution proposed here exploits the determinism of a train's route and the potential availability of information specific or non-specific to the railway domain to anticipate reconfigurations of the hybrid communications system. The density score is understood to be a qualitative value regarding the density of potential users of the access network.

[0034] The user density associated with an access network is linked to network occupancy. It can be evaluated using methods specific to access networks, for example, specific applications that query the core network to obtain information about the number of users in 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 edge radiocommunication equipment 101 is located, and to deduce a density score associated with the access network in question, for example, by calculating a density by dividing the available bandwidth 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 evaluated by methods specific to railway applications, for example: - based on CCTV (closed-circuit television) data, which allows for the assessment of train occupancy. This information can be used to approximate the number of users utilizing available public access networks and to estimate an associated density score. - using CCTV data from the platforms, which allows for an assessment of platform occupancy. Advantageously, a crowd counting solution makes it possible to accurately count the number of people on the platforms. It is then possible to estimate a density score associated with the available public access networks. - based on station / train occupancy information obtained from a Remote server. For example, it's possible to know fairly precisely the number of people on the train and on nearby trains, using information from the ticketing system. It's also possible to know approximately the number of people on the platforms from information provided by access gates. It's 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 near the routes that may impact user density, such as road traffic, the presence of demonstrations, 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 comparing, for each access network, the density score with a threshold. The threshold associated with each access network can take into account the specific characteristics 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 data rates required for the edge-to-ground communication link. It can be established in such a way 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 data rate, and network availability.The threshold should be positioned so that a density score exceeding it indicates that the access network is highly 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 includes a step 202 for evaluating the optimal configuration of the edge-to-ground communications link, taking into account the results of step 201. This step consists of determining the most suitable access network, and possibly the data rates, for implementing the edge-to-ground communications link. It can be implemented in various ways.

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

[0041] Advantageously, when two access networks with density scores below the threshold have the same characteristics (same radio link quality, and / or same cost of use, ....), the access network to be preferred for implementing the edge / ground communications link is the one with the lowest density score.

[0042] According to one embodiment, access networks whose density score is greater than the threshold in step 201 are eliminated from a list of usable access networks for the implementation of 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 according to the geographical position of the on-board radio communications equipment 101.

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

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

[0045] Reducing the communication link speed can be done in various ways, such as: - by transmitting only priority services (voice, data, signaling, etc.) over the ship-to-ground communication 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 includes a step 203 of configuration of the edge / ground communications link in accordance with the access network and transmission parameters (rate) determined during the second step 202. This step includes, when necessary, the re-parameterization and reconfiguration of the communications link ensuring edge / ground connectivity.

[0048] The method for selecting an access network according to the invention can be implemented by the onboard radiocommunication equipment 101, but also by remote equipment, transmitting the configuration calculated during step 202 to the onboard radiocommunication equipment 101 so that it can implement step 203 of the process. This equipment can, for example, be ground station 111 or any device with computing means capable of retrieving the metrics necessary for the implementation of the process, executing steps 201 and 202, and transmitting information on the configuration of the onboard / ground communications link to the onboard equipment 101.

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

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

[0051] The method for selecting an access network according to the invention makes it possible to obtain higher quality network connectivity than state-of-the-art methods for train-to-ground communication links, while minimizing the risk of service interruptions. It leverages the determinism of railway routes to define simple and effective criteria for reassessing / reconfiguring train-to-ground connectivity. It makes it possible to anticipate network congestion and availability issues and to dynamically adapt the hybridization strategy to the environment of the onboard radiocommunication equipment. Unlike hybridization based exclusively on network metrics, it can be implemented non-intrusively. Indeed, the information necessary for density calculation is available from railway operators and radiocommunication operators.

[0052] Advantageously, the method of selecting an access network according to the invention includes an additional step 204 of verifying the applicability of the optimal configuration of the edge / ground communications link determined during step 202. This step is a prerequisite to step 203 of configuring the edge / ground communications link.

[0053] It consists of verifying whether the configuration determined during step 202 is compatible with the environment of the onboard radiocommunication equipment 101, for example by checking that: - The recommended access network is indeed available, - The required bandwidth is compatible with the selected access network. - the technology in question is compatible with the speed of the train (so as to rule out, for example, a situation where a train passing through the station without stopping would switch to the station's wifi network), - The availability period of the selected access network is sufficient with regard to the movement of the rail 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 over links with limited bandwidth, or over links particularly susceptible to congestion, - etc.

[0054] If the optimal configuration is applicable for the radiocommunication equipment 101, then the process proceeds to the next step 203. Otherwise, the process returns to step 202, with the aim of finding another configuration of the edge / ground communications link.

[0055] The invention relates to the method for selecting an access network described above, but also to: - an onboard radiocommunications equipment 101, configured to implement a method for selecting an access network according to an embodiment of the invention, - a system, comprising a computing means configured to implement steps 201, 202 and optionally 204 of a method for selecting an access network according to the invention, and then to transmit the resulting configuration to onboard radiocommunication 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 process when 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 density score associated with said access networks, and using this density score when making a decision concerning the configuration of said communications link.

2. Method for selecting an access network according to claim 1, comprising: - a first step (201) of determining a density score and comparing said 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 by taking into account the results of the first step, - a third step (203) of configuring said communications link in accordance with the optimal configuration evaluated during the second step.

3. A method of selecting an access network according to claim 2, wherein the density score calculated in the first step (201) is used in the second step (202) to select the access networks that can be used to implement said communications link.

4. Method for selecting an access network according to one of claims 2 and 3, in which the second step (202) comprises adapting the flow rate of said communications link as a function of the density score calculated during the first step (201).

5. Method for selecting an access network according to one of claims 2 to 4, in which the second step (202) further comprises measurements of the quality of radio links on the different access networks.

6. Method for selecting an access network according to one of claims 2 to 5, in which the threshold used during the first step (201) is depending on the type of access network.

7. Method for selecting an access network according to one of claims 2 to 6, further comprising a step (204) of verifying the applicability of the optimal configuration evaluated during the second step (202).

8. 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).

9. 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 8.

10. 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 8.

11. 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 8 when said computer program is executed on a computing means. 13

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