On-board method and system for selecting communication channel between aircraft and remote station

Abstract

The invention relates to an onboard method and system for selecting a communication channel between an aircraft and a remote station. The method for selecting a communication channel, referred to as a utilization channel, comprises: a step of determining, for each communication channel, one or more items of information representing the transmission quality of a message, where the message is a "useful" message received by an onboard system, or a probe message, referred to as "ping" message; a step of classifying the communication channels according to indicators indicating transmission quality, respectively, on the basis of the information; a step of selecting a utilization channel as a communication channel exhibiting the optimal transmission quality on the basis of the index; a step (101) of determining a buffer time for each received useful message; and a step (102) of transmitting a useful message, referred to as a qualified useful message, rather than a ping message, if the time is non-zero.

Description

Technical Field

[0001] The present invention relates to an onboard method and system for selecting a communication channel from a plurality of communication channels between an onboard communication system of an aircraft and a communication station located remote from the aircraft, for example on the ground. Background Art

[0002] Aircraft most often use systems for transmitting data to one or more ground stations, allowing operators to establish radio monitoring of the aircraft by obtaining various items of operational and logistical information in a detailed manner, such as, for example, the aircraft's location and its status, as well as information about any malfunctions. This allows maintenance actions to be organized in advance and carried out after the aircraft has returned to the ground. A known system of this type is generally known as ACARS (Aircraft Communications Addressing and Reporting System). This system relies on communication means initially based on HF and VHF communication channels and more recently on SATCOM-type satellite links, particularly in oceanic areas.

[0003] In many flight situations, several communication channels are available simultaneously, and the transmission quality on these channels can vary depending on the type of channel. In some applications, a list defining channel usage preferences is statically defined in a database onboard the aircraft. Furthermore, sometimes a channel can be selected over another based on operational cost.

[0004] However, such practice may result in the use of a transmission channel that is not the most efficient at a given moment. Furthermore, depending on the method used to monitor and manage transmission quality, the continuous switching of transmission channels may prove to be counterproductive, and a good balance must be found between the advantages that a change of channel can provide and the risks inherent in switching too frequently.

[0005] Document FR 2202302 discloses a method for selecting a channel (referred to as a utilization channel) from among a plurality of communication channels between an aircraft and a remote station, which method associates a transmission quality indicator with each channel and allows the selection of the best communication channel in real time. This method ensures increased reliability of data transmission between an aircraft and a remote station by optimizing the selection of a transmission channel and the conditions for switching from one channel to another, thereby minimizing any risk of service interruption.

[0006] To this end, the prior art method envisions analyzing the transmission of two types of messages. The first type of message consists of so-called useful messages, which contain information that must be sent from the aircraft to the remote station. The second type of message consists of ping messages, which are sent periodically and are intended to be analyzed to determine transmission quality indicators. These ping messages ensure that the selection method is functioning properly even when no useful messages are being sent.

[0007] However, this method involves sending ping messages at regular intervals in addition to useful messages, and it would be beneficial to limit the increase in information traffic that results from this.

[0008] The object of the present invention is to at least partially overcome these disadvantages. Summary of the Invention

[0009] To this end, a method is proposed for selecting a communication channel, referred to as a utilized channel, from a plurality of communication channels between an onboard communication system of an aircraft and a communication station, referred to as a remote station, located at a certain distance from the aircraft. The method comprises:

[0010] - a step of determining, for each of the communication channels, one or more items of information representative of the transmission quality of messages between the onboard communication system and the remote station, the messages being "useful" messages received by the onboard communication system or probing messages known as "ping" messages, which are sent within a given period of time;

[0011] - a step of classifying the communication channels according to an indicator respectively representative of the transmission quality determined for each of the communication channels, based on the determined information, wherein a single indicator is assigned to each communication channel;

[0012] - Step of: selecting the utilization channel as the communication channel exhibiting the best transmission quality among the communication channels based on the indicator;

[0013] The method further includes:

[0014] - step of determining a buffer time called qualification time for each received useful message; and, if the qualification time is non-zero,

[0015] - Step: Sending a useful message, called a qualified useful message, instead of a ping message via the utilization channel.

[0016] Thus, by means of the method according to the invention, the ping message traffic is reduced, which limits the mobility of the communication system and ensures a good quality of the communication network, while reducing the costs resulting from the selection of better channels.

[0017] It should be noted that "useful" messages received by the onboard communication system are understood to mean messages sent to the onboard communication system by the source transmission application itself onboard the aircraft, that is, messages entrusted by the source transmission application to the onboard communication system to be sent to the remote station, which should not be confused with messages received from the ground station.

[0018] According to another aspect, the method comprises a step of analyzing the buffer of qualified useful messages, including a checking step that depends on the state of the buffer memory and on parameters associated with the qualified useful messages.

[0019] According to another aspect, the onboard communication system comprises at least one buffer memory, wherein the step of analyzing the buffer of qualified useful messages comprises the step of determining a sequence for filling the at least one buffer memory.

[0020] According to another aspect, the onboard communication system comprises a respective buffer memory for each channel, wherein the step of analyzing the buffer comprises the step of determining an order for filling said buffer memories.

[0021] According to another aspect, the step of determining the filling order comprises the steps of calculating the duration between the transmission of at least the next ping message on each channel and the time of reception of a qualified useful message by the onboard communication system, and sorting the obtained durations in ascending order, wherein the buffer memory filling order follows the obtained sorting.

[0022] “Receiving time” is understood to mean the maximum time for storing an eligible useful message.

[0023] According to another aspect, during the step of comparing the state of the buffer memory with the parameters of the qualified useful message, for the communication channel whose buffer memory is to be filled first according to the order obtained when the step of determining the filling order is completed, if the buffer memory is empty and if the maximum message buffering time is greater than the duration remaining until the next transmission of the ping message, the qualified useful message is placed in the buffer memory during the step of analyzing the buffer.

[0024] According to another aspect, if the maximum message buffer time is less than or equal to the duration remaining until the next sending of a ping message, the eligible useful message is not placed in the buffer memory and is sent as a useful message during the sending step.

[0025] According to another aspect, in which the onboard communication system comprises a buffer memory common to all communication channels, during the step of comparing the state of the buffer memory with the parameters of qualified useful messages, the number of messages contained in the buffer memory, referred to as the number of messages, is compared with the total number of ping messages, referred to as the number of pings, to be sent within a time equal to the maximum message buffering time, and if the number of pings is greater than the number of messages, then during the step of analyzing the buffer, the qualified useful message is placed in the buffer memory.

[0026] According to another aspect, if the number of pings is less than or equal to the number of messages, the eligible useful message is not placed in the buffer memory and is sent as a useful message during the sending step.

[0027] Another object of the invention is an onboard communication system intended to equip an aircraft, configured to establish communication with a remote communication station via a communication channel, called the "best channel", among a plurality of communication channels, wherein the onboard communication system comprises electronic and electromagnetic circuits configured to implement the following steps:

[0028] - a step of determining, for each of the communication channels, one or more items of information representative of the transmission quality of messages between the aircraft and the remote station, the messages being "useful" messages received by the onboard communication system or being probe messages, known as "ping" messages, sent within a given period of time;

[0029] - a step of classifying the communication channels according to an indicator respectively representative of the end-to-end transmission quality determined for each of the communication channels based on the determined information, wherein a single indicator is assigned to each communication channel;

[0030] - Step of: selecting the utilization channel as the communication channel exhibiting the best transmission quality among the communication channels based on the indicator;

[0031] - step of determining a buffer time, called qualifying time, for each received useful message; and, if the qualifying time is non-zero, step of sending a useful message, called qualifying useful message, instead of a ping message.

[0032] More generally, the onboard communication system is configured to implement the selection method as described above.

[0033] Another object of the invention is an aircraft comprising an on-board communication system.

[0034] Another object of the invention is a computer-readable medium comprising instructions for executing the method as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Further features, details, and advantages will become apparent from reading the following detailed description and from analyzing the accompanying drawings, in which:

[0036] Figure 1 is a schematic representation of a communication system for transmitting data between an aircraft operating on the ground or in flight and a communication station remote from the aircraft;

[0037] Figure 2 is shown for evaluation Figure 1A flowchart of the overall sequence of a method for determining the performance of each of the available communication channels between the aircraft and the remote station 3;

[0038] Figure 3 shows the step of selecting, from channels C1 , C2 and C3 , a communication channel known as the best available communication channel between the aircraft 2 and the remote station 3 ;

[0039] Figure 4 A flow chart showing a selection method according to the present invention is shown;

[0040] Figure 5 According to the first embodiment, Figure 4 Examples of methods;

[0041] Figure 6 According to the second embodiment, Figure 4 Examples of methods;

[0042] Figure 7 An example of the internal architecture of an onboard system according to the present invention is shown. DETAILED DESCRIPTION

[0043] The examples and associated conditions described herein are primarily intended to help the reader understand the principles of the present invention, rather than to limit the scope of the present invention to these specific examples and conditions. It should be understood that those skilled in the art may envision various arrangements that, although not explicitly described or represented herein, embody the principles of the present invention and are included within the spirit and scope of the present invention.

[0044] In addition, for ease of understanding, the following description may describe a relatively simplified implementation of the present invention. As those skilled in the art will appreciate, other implementations of the present invention may be more complex.

[0045] In some cases, variations of the present invention may be presented. This is intended to aid understanding and is not intended to limit the scope of the invention or to establish limitations thereto. These modifications are not an exhaustive list, and those skilled in the art will be able to make other modifications while remaining within the scope of the invention.

[0046] In addition, all statements below relating to the principles, aspects, and implementations of the present invention, as well as specific examples of the present invention, are intended to encompass both structural and functional equivalents of the present invention, whether currently known or developed in the future. Thus, for example, it will be understood by those skilled in the art that all functional diagrams represent conceptual views of examples of circuits incorporating the principles of the present invention. Similarly, it will be clearly understood that all flow charts, state transition diagrams, pseudocode, etc. represent various methods that can be implemented on a computer-readable medium and, therefore, can be executed by a computer or processor, whether or not such a computer or processor is shown in the accompanying drawings.

[0047] The functions of the various elements shown in the drawings (including any functional blocks) can be provided by using dedicated hardware as well as hardware capable of executing appropriate software. These functions can also be performed by a processor. Other conventional and / or custom hardware can also be used.

[0048] A software module, or a module considered to be software, may be represented herein as a combination of flow chart elements, or a combination of other elements indicating the execution of steps of a process, and / or as a textual description. Such a module can be executed by hardware that may or may not be explicitly represented. Furthermore, it should be understood that a "module" may include, for example, but not limited to, computer program logic, computer program instructions, software, a software stack, firmware, hardware circuitry, or a combination of these various elements that provide the desired capabilities.

[0049] As can be seen from the accompanying drawings, the present invention relates to a method 100 for communicating from a communication system 1 of an aircraft 2 to a communication station located at a certain distance from the aircraft (at Figure 1 Another object of the present invention is a communication system 1 for implementing the method 100 .

[0050] In the following description, it is assumed but not limited that the system 1 includes three communication channels C1 , C2 and C3 .

[0051] Communication system 1 comprises an onboard communication system 4 equipping aircraft 2, and a system 5 (referred to as a ground system) equipping remote stations 3, located at a distance from onboard system 4. System 1 also comprises transmission equipment 6 for channels C1 to C3 for transmitting information between aircraft 2 and remote stations 3.

[0052] Preferably, the onboard system 4 comprises a router 7. The system 4 also comprises an onboard application configured to ensure any downlink of information traffic to the ground and optionally to receive information from the onboard system 5.

[0053] Preferably, the ground system 5 comprises a router 9. The system 5 also comprises an application for receiving information traffic originating from the onboard system 4 and optionally for sending uplinks to the onboard system 4.

[0054] The transmission equipment 6 comprises communication means originally based on HF and / or VHF and / or SATCOM type transmission channels, and / or any other communication means used in aviation, such as an L-DAC, for example, or a "virtual" communication channel, such as a local link (in particular of Ethernet type) to the cabin system, as seen from a router, which agnostically provides multiple physical links.

[0055] Advantageously, and with the aid of communication system 1, aircraft 2 can transmit a wide variety of data to remote station 3, in particular for the purpose of accurately locating the aircraft during flight or after returning to the ground, and also for the organization of management, operational, and maintenance activities. Furthermore, the aircraft's communication system allows for the provision of relevant information useful for the operation of the aircraft, such as, for example, meteorological information or information related to the flight plan of the aircraft or of third-party aircraft.

[0056] The onboard system 4 is configured to perform the method 100 .

[0057] As known from document FR 2202302, the “best channel” is selected based on at least one primary communication performance criterion and optionally other secondary communication criteria. The term “performance criterion” as used herein refers to a criterion used to assess the end-to-end (between an aircraft and a remote communication station) transmission quality or the quality of a transmission link.

[0058] Preferably, the primary communication performance criterion is the latency of the channel under consideration, while secondary criteria that are optionally considered are communication performance quality criteria, such as, for example, the signal-to-noise ratio or information representing the use of the channel (usage rate, duration of continuous use, error rate, etc.).

[0059] According to a variant, the main performance criterion used to evaluate the end-to-end transmission quality is a criterion other than latency, representing the quality of transmission via the communication channel, such as, for example, the signal-to-noise ratio or information representing the use of the channel (usage rate, duration of continuous use, error rate, etc.), optionally weighted by one or more secondary criteria.

[0060] The latency of a channel is defined herein as the total travel time for data sent from aircraft 2 to remote station 3 and then sent back from remote station 3 to aircraft 2. The latency thus defined can be expressed as the sum of the "downlink" latency (from aircraft 2 to station 3) and the "uplink" latency (from station 3 to aircraft 2), preferably ignoring the local processing time of remote station 3.

[0061] According to one embodiment, the delay of a channel is determined by an indicator representing a determined delay value or a set of continuously determined delay values. The determined delay values ​​primarily form information for determining a single delay indicator for each channel. In other words, a delay indicator specific to a given channel, such as, for example, a minimum delay, a maximum delay, or even an average or median delay, can be determined based on the determined delay value or based on a set of determined delay values ​​for a given channel within a given time interval. When the delay indicator is determined for each of the communication channels, the communication channels are classified by the indicator. Therefore, the lowest delay indicator corresponds to the delay indicator of the communication channel that is detected as providing the best communication performance from the available channels, while the highest delay indicator corresponds to the delay indicator of the communication channel that is detected as providing the worst communication performance, or vice versa. According to one embodiment, information representing the delay of the channel at a given moment is determined from the transmission that has just been established by determining the end-to-end travel time of the data packet.

[0062] According to another embodiment, information representing the latency of a channel at a given moment is determined by using a "ping" function commonly used in communication networks, in particular computer networks, and based on a communication protocol such as TCP (Transmission Control Protocol) or ICMP (Internet Control Message Protocol). Generally, the ping function is a computer command designed to test the accessibility of a remote machine through a communication network and, if the remote machine is accessible, measures the time it takes to receive a response, also known as the "round trip time" (RTT).

[0063] According to another embodiment, the latency of the communication channel is determined based on "useful" communication established via the communication channel, and in the absence of sufficient regular communication, a ping function is used in addition to the "useful" communication. When the latency is defined based on "useful" communication established via the communication channel, the one or more data packets used to determine the latency include information similar to that used in the message implementing the ping function.

[0064] The distribution between the transmission of user messages and ping messages is described below in conjunction with the description of method 100 .

[0065] After characterizing the latency of the various communication channels available between aircraft 2 and remote station 3, and therefore the performance capabilities of these various channels (i.e., channels C1, C2, and C3), onboard system 4 can check whether the channel providing the best communication performance is still the channel initially used (i.e., at the beginning of activation of method 100, for simplicity, it is assumed to be the first channel C1), and if applicable, change the utilized channel. Thus, if onboard system 4 detects that the channel determined to be the best channel is not the channel through (via) which the first communication was established, the system, while simultaneously establishing the first communication through the first channel, begins establishing the second communication through the second communication channel that is the best detected communication channel. In this configuration, the transmissions established between aircraft 2 and remote station 3 are redundant, and the remote ground station manages the redundancy of the data it receives by eliminating duplication.

[0066] The onboard system 4 scans the evolution of the classifications it has assigned to the channels according to their performance over a predetermined period DP, so that if, at the end of the period DP, the second channel is still the best channel, the first communication established via the first channel is interrupted. In this case, the second communication channel, which is now the only communication channel, "becomes" the first channel, and the second communication "becomes" the first communication, and the method for determining the best channel continues to operate on this new basis. Otherwise, the onboard communication system 4 continues to establish the first communication via the first communication channel. According to one variant, in order for the onboard communication system 4 to stop establishing the first communication and switch channels between the first communication channel and the second communication channel (determined to be the best communication channel), the second channel must not only be the best channel at the end of the delay DP, but also remain the best channel throughout the delay DP, which tends to indicate and means that it can be checked that the second communication channel is sufficiently reliable at that moment, or at least that it provides performance capabilities that meet expectations at that moment. This also allows the creation of a time filter that avoids switching channels when the relative situation of the various channels is not fundamentally stable in terms of performance capabilities (transient phenomena).

[0067] According to one embodiment, the onboard system 4 of the aircraft 2 transmits the classification of the channels by performance indicators to the remote station 3, so that the remote station 3 is informed of the relative quality of the communication channels evaluated by the aircraft 2. This information can be sent to the remote station 3 in the form of data encoded and identified according to a predetermined protocol. For example, the packet header has an identifiable identifier and includes several channels, followed by a list of channel identifiers classified in ascending or descending order of performance. Thus, in the case where uplink communication is not established via the same communication channel as the communication channel used to establish downlink communication, the remote station 3 can select the communication channel used to establish the uplink communication. According to one embodiment of the present invention, the remote station 3 establishes any uplink communication on the last channel used for downlink communication. According to a variant, the remote station 3 uses the channel performance related information received from the aircraft to select the channel to be used for subsequent uplink communication.

[0068] Advantageously, various channel delay estimation techniques can be implemented to estimate delays depending on the type of channel being used. For example, a delay estimation for a first channel can be performed using a ping network command (or function) based on the ICMP protocol, and a delay estimation for a second communication channel can be performed using a ping network command based on the TCP protocol. Following similar reasoning, only downlink delay is used to classify channels according to performance capabilities.

[0069] According to one example, in terms of downlink latency, the latency of the communication channel can be determined by subtracting the time it takes for the remote station 3 to send a message from the onboard system 4 from the time it receives the same message. According to another example, the latency of the channel can be determined by subtracting the time it takes for the remote station 3 to receive a confirmation of receipt of the message sent by the aircraft from the time it is sent by the aircraft's onboard system 4. Furthermore, an approximation can be made to determine the latency of the uplink or downlink as half the round-trip time (RTT).

[0070] In the case where a ping function is used to determine latency, the ping network command or function includes information useful for its correct execution, namely, a ping command identifier, a sender identifier, a receiver identifier, a sending time, a receiving time by the receiver, a link type, one or more message (command) routing device identifiers, a quality indicator determined by the aircraft for the channel being used, etc. This list of examples is not exhaustive.

[0071] Advantageously, the evaluation of the channel performed by the onboard system 4 may include other parameters such as, for example, a link quality indicator (e.g., signal-to-noise ratio), a transmission error rate via the relevant link, "jitter" (which is defined as the variation of the delay over time), a number of delay measurements performed within a predetermined time interval (in order to indicate the reliability of the determined delay), and the occupancy rate of the communication channel. For example, the delay indicator determined for each channel may be weighted by a weighting factor defined for each channel by a transmission quality indicator and / or by an indicator representing the use of the channel under consideration within a predefined time interval.

[0072] According to one embodiment, onboard system 4 simultaneously executes a first method for evaluating the performance of each channel and classifying the channels according to a metric determined for each channel primarily based on the channel's latency, and a second method for selecting the best communication channel from the classification performed in the background. These two methods are actually two sub-methods of the overall method for selecting a communication channel according to the present invention.

[0073] Figure 2 1 is a flowchart showing the overall sequence of a method (or more specifically, a sub-method) for evaluating the performance of each communication channel available between an aircraft 2 and a remote station 3, for defining a single indicator for each channel determined according to the channel's latency, optionally weighted by another transmission performance indicator, and then for sorting the communication channels according to the determined indicator in order to define a predetermined order from the best communication channel to the worst communication channel, or vice versa.

[0074] As in Figure 2 As can be seen in FIG, step S0 is a step of initializing the aircraft system 2, at the end of which the aircraft system is supplied with electrical energy, initialized and operating normally. In particular, the onboard system 4 is configured to be able to establish a first communication, in particular a first communication to the remote station 3, on a first available and selected communication channel.

[0075] During a step S1 , ping commands are executed at regular intervals on all communication channels available between the aircraft 2 and the remote station 3 in order to define one or more items of delay information for each channel.

[0076] According to one example, the ping command execution frequency is such that the ping command is sent once every x seconds, where x ranges, for example, between 1 second and 60 seconds, such as 2 seconds, 6 seconds, 8 seconds, 10 seconds, or 30 seconds. However, the frequency of measuring the time delay of the communication channel can be increased or decreased based on the results observed on each communication channel. In addition, the evaluation frequency of each channel can vary from one channel to another, particularly depending on the type of channel.

[0077] According to method 100, as will be described below, "useful" communications can be sent instead of ping messages, or even frequently enough to avoid the use of ping commands, and the current communications are used to define the latency of each of the available communication channels. The data packets exchanged through the channels then contain all the useful information required to determine the latency, i.e., information equivalent to the information present in the ping command used to calculate the latency. A range of latency values ​​and an average latency value can be defined for each communication channel C1, C2, C3, and a latency metric can be determined based on this latency information. For example, the latency metric can be determined so that the channel with the highest latency is assigned a latency metric of 10 and the channel with the lowest latency is assigned a latency metric of 0, or vice versa, depending on the metric definition convention used. Typically, in the airborne communication system 4, the latency values ​​are expressed in seconds. Therefore, the latency of each channel is evaluated over a duration T1 (typically several minutes).

[0078] During step S2, the delay indicators defined for each channel are recorded in a table, and the channels are sorted in this table in order of performance (delay or weighted delay). The channel sorting table is stored, for example, in a volatile or non-volatile memory of the onboard communication system 4 of the aircraft 1. Step S3 involves identifying the communication channel whose indicator represents the best communication performance, so that the improved method for selecting a communication channel executed by the onboard system 4 can identify the channel exhibiting the best communication conditions to the remote station 3 by sampling the memory.

[0079] After step S3, the method loops back to step S1, meaning that the channel delay is continuously evaluated in the background by the onboard system 4 of the aircraft 2. These operations are performed during step S1, with secondary information representing the transmission quality of the channel being used to weight the channel's delay indicator, and the weighted indicator is taken into account in the classification performed in step S2. In this case, the information representing the transmission quality is defined as a protocol and is transmitted during the message exchange between the aircraft 2 and the remote station 3, but can also optionally be transmitted from a third-party communication to a reference device.

[0080] Figure 3The step of selecting a communication channel, cited as the best available communication channel between aircraft 2 and remote station 3, from channels C1, C2, and C3 is shown. Again, more precisely, this is a sub-method of the improved method for selecting a communication channel according to the present invention, since, according to the described embodiment, the two sub-methods, executed simultaneously, perform the steps of the complete method. Step S0' corresponds to the step of initializing the systems of aircraft 2, at the end of which the systems are supplied with energy, initialized, and operating normally. In particular, onboard system 4 is configured to establish a first communication, in particular, to remote station 3, on the first available and selected communication channel. According to one embodiment, steps S0 and S0' are combined into a single step of the aircraft, referred to as the "startup" step. During step S10, after selecting the first communication channel to remote station 3, onboard communication system 4 of aircraft 2 sends initial information (data) to remote station 3. Then, during step S20, it waits for a duration DP1 (typically ranging from several seconds to several minutes) until the best channel can be determined in the background, so that, at the end of step S30, it can be determined whether the first channel selected for establishing the first communication is the best channel. If, in step S30, the channel currently in use (i.e., the first channel) is determined to be the optimal channel, the method loops back to step S10 and thus continues to establish communication with the remote station via the first channel. Otherwise, that is, if the current channel is not the optimal channel, the method initiates an additional communication (in this case, again referred to as the second communication) during step S40 via a second communication channel, which is precisely the channel determined to be the optimal channel by reading information contained in the memory of the onboard system 4 and updated by the successive executions of method 100. A new waiting phase of duration DP2 is then executed during step S50, the purpose of which is to create a "time filter," that is, to be able to check whether the second channel continues to provide optimal communication performance capabilities at the end of delay DP2. To this end, at the end of delay DP2, a new phase of reading the optimal communication channel is executed during step S60. According to one embodiment of the invention, duration DP2 ranges, for example, from 1 minute to 4 minutes, for example 2 minutes.

[0081] In the event that the second channel is still the best channel at the end of delay DP2, the first communication established on the first channel is stopped during step S70 and the method loops back to step S10. In this case, the second channel is then considered to be the first channel for repeating the described sub-method and the second communication is then considered to be the first communication. Otherwise, that is, if during step S60 another channel is determined to be the best communication channel at the end of delay DP2, the second communication established on the second channel is stopped during step S80 and the first communication continues to be established on the first channel, and the method loops back to step S10. Advantageously, and according to one embodiment of the invention, steps S50 and S60 involve checking that the second communication channel remains the best communication channel for the entire duration of delay DP2. Otherwise, additional information is defined (an indicator of the change of the best channel during delay DP2) allowing the result of the test performed during step S60 to be enforced.

[0082] According to one embodiment of the invention, the described selection method can be deactivated by an operator in the aircraft or on the ground in order to then select a communication channel from a second selection method using, for example, statically defined communication channel preference criteria.

[0083] Now refer to Figure 4 .

[0084] As can be seen from the figure, during step S1, the method 100 further comprises:

[0085] - a step (101-TAMP) of determining a time Tbx (called eligibility time) for buffering each received useful message Mx; and, if the eligibility time is non-zero,

[0086] - A step of sending a useful message as a PING message (ie, instead of a PING message) (102-ENV ping).

[0087] The buffering time Tbx may be, for example, a maximum possible buffering time, taking into account a delay considered acceptable for the message and optionally a transmission delay of the communication network. More generally, the buffering time may be any time characteristic of an acceptable buffering time.

[0088] A "non-qualified message" is a useful message with a zero buffer time. A "qualified message" is a useful message with a non-zero buffer time. For these messages, method 100 preferably includes a step (103-RAM) of analyzing the buffer of useful messages in step S1, wherein the message (instead of the ping message) has been sent at the appropriate time during step 102, as will be described below.

[0089] Thus, by buffering useful messages to be sent as quickly as possible instead of ping messages, method 100 reduces the number of messages exchanged between aircraft 2 and remote station 3 , which preserves communication network 1 , reduces the energy required to operate system 1 , and reduces associated costs.

[0090] As a reminder, for each channel C1, C2, C3, the system 4 sends pings at a set frequency. Tp1 indicates the period during which ping P1 is sent on channel C1, Tp2 indicates the period during which ping P2 is sent on channel C2, and Tp3 indicates the period during which ping P3 is sent on channel C3.

[0091] from Figure 4 It can also be seen that, since the system 4 includes at least one buffer memory, the step 103 of analyzing the buffer of qualified useful messages includes a step (104-ORD TAMP) of determining the order for filling the at least one buffer memory, which step (104-ORDTAMP) is described below for each of the two described embodiments.

[0092] from Figure 4 It can also be seen that step 103 of analyzing the buffer of qualified useful messages includes a checking step (105-VER) depending on the state of the buffer memory and parameters related to the qualified useful messages, which step (105-VER) is described below for each of the two described embodiments.

[0093] A first embodiment will now be described.

[0094] According to a first embodiment, each channel C1 , C2, C3 has a corresponding buffer memory, denoted B1 , B2, B3. According to this non-limiting embodiment, the buffer memories B1 to B3 have space for only one message.

[0095] According to this embodiment, Figure 4 and Figure 5 As shown in , step 103 comprises a preliminary step (104-ORD TAMP) of determining the order for filling memories B1, B2, B3. Memories B1, B2, B3 are filled in an order following a rule called the next ping rule, which will be explained below.

[0096] During a step 104 , the method 100 calculates, for each channel and at a given time T0 for receiving a message, the duration remaining until the subsequent ping or pings are sent.

[0097] It should be noted that in this specification, "receiving a useful message" or "receiving a useful message" corresponds to a message initiated by an onboard source application of the message and received by (or sent to) an onboard communication system responsible for managing communications with the ground.

[0098] In other words, the time difference between each of the times Tp1, Tp2, Tp3 and T0 is determined, and if applicable, the time difference between the periods Tp1 (Tp1', Tp1") to Tp3 and multiples of T0 is determined, and each difference D is sorted in ascending order.

[0099] The order for filling the buffer memories B1, B2, B3 is derived from this: the memory to be filled first or the priority memory is the memory that exhibits the smallest time difference Tmin for its channel, the second priority memory is the memory other than the priority memory that exhibits a smaller time difference (after Tmin) for its channel, and so on, until all memories are evaluated.

[0100] Each time a qualified useful message Mx is received by the onboard system 4 , the method 100 comprises a step ( 105 -VER) of checking the filling status of the priority buffer memory Bi.

[0101] If the fill status is not empty, the fill status of the second priority buffer memory is checked.

[0102] If the fill status is empty, method 100 includes a step of comparing the time D remaining until the next ping message is sent on channel Ci of buffer memory Bi with the maximum message buffer time Tbx. If time Tbx is greater than time D, message Mx is placed in buffer memory Bi during step 103. Otherwise, during a sending step (106-ENVut), message Mx can no longer be delayed and is sent as a useful message.

[0103] The method 100 then includes the step of reinitializing the sequence of ping messages (107-INIT).

[0104] With particular reference Figure 5 , which shows an example of implementation of a first embodiment of the method 100 , which is of course not limiting.

[0105] As can be seen from the figure, three communication channels C1, C2 and C3 are considered. Each channel has a "ping" period of 2s (for C1), 4s (for C2) and 8s (for C3) respectively.

[0106] Three consecutive messages, denoted as Ma, Mb, and Mc, will be considered. Each of the messages Ma, Mb, and Mc has a maximum buffering time, denoted as Tba, Tbb, and Tbc respectively, such that Tba = 8s, Tbb = 10s, and Tbc = 1s.

[0107] Message Ma is received by the airborne system 4 at T0. Message Mb is received by the system 4 at T0 + 0.5s. Message Mc is received by the airborne system 4 at T0 + 3.5s.

[0108] In Figure 5 , Tp1 represents the transmission time of the first "ping" P1 on channel C1 immediately following T0, Tp'1 represents the transmission time of the "ping" P'1 after the "ping" P1 on channel C1, Tp2 represents the transmission time of the first "ping" P2 on channel C2 immediately following T0, and Tp3 represents the transmission time of the first "ping" P3 on channel C3 immediately following T0.

[0109] In Figure 6 it is selected that T0 = Tp1 – 1s = Tp2 – 2s = Tpз – 3.5s.

[0110] In Figure 6 the example in, four "pings" are considered.

[0111] During step 104, the priority order for filling the buffer memory is defined according to the next "ping" to occur. As already indicated, during step 101, each of the following differences is calculated: D1 = Tp1 – T0 = 1s; D2 = Tp2 – T0 = 2s; D3 = Tp3 – T0 = 3.5s; D1' = Tp1' – T0 = 3s.

[0112] In this case, D1 < D2 < D1' < D3. Therefore, the "pings" will be P1, P2, P1', and P3 in sequence. This results in the following order for filling the memory: B1, then B2 and B3.

[0113] Step 105 involves determining whether message Ma can be buffered and, if so, on which channel.

[0114] In this case, according to the established order for filling the memory, this involves knowing whether message Ma can be buffered in memory B1. Two conditions must be met, namely:

[0115] - B1 is empty, which is the case here; and

[0116] - the maximum buffering time is greater than the ping time P1.

[0117] By comparing D1 with Tba, it can be seen that D1 = 1s < Tba = 8s. Therefore, the message Ma is effectively buffered in the memory B1.

[0118] The message Mb is received by the system 4 at time T0 + 0.5s.

[0119] Since the memory B1 is full, if B2 is empty and the maximum time Tbb of the message Mb is greater than the ping time P2, the message Mb can be buffered in the memory B2, that is, in this case, because DD2 = Tp2 – (T0 + 0.5) = 1.5s < Tbb = 10s.

[0120] Therefore, the message Mb is buffered in the memory B2.

[0121] At time T0 + 1s, the message Ma instead of the "ping" P1 is sent to the remote station 3 through the channel C1.

[0122] At time T0 + 2s, the message Mb instead of the "ping" P2 is sent to the remote station 3 through the channel C2.

[0123] At time T0 + 3s, it is the turn of the first channel C1 to send a "ping" again. Since the memory B1 is empty, no message can be sent as a "ping", and then a "ping" is sent through the channel C1.

[0124] At time T0 + 3.5s, the message Mc is received by the system 4. ​​​​​​​​​​​​​​​​Then, in step 107 , the timing of the “ping” period of channel C2 is reset to the sending time of message Mc. Upon receipt of the next useful message, method 100 can re-establish the order for filling memories B1 , B2 , B3 according to step 104 .

[0131] According to a second embodiment, the buffer memory B is shared by the three channels C1, C2, and C3. It should be noted that according to this embodiment, the method 100 always maintains the temporal order of the pings. It should also be noted that according to this embodiment, the buffer memory has a variable size.

[0132] According to this embodiment, Figure 4 and Figure 6 As shown in , method 100 comprises a step (105-VER) of comparing the state of buffer memory B with a parameter associated with qualified useful messages. The state of buffer memory B corresponds to the number Nm of useful messages contained in buffer memory B. The parameter associated with qualified useful messages is the number of pings to be sent on the three channels C1, C2, C3 during the maximum buffer time Tb, Np.

[0133] If the number Np of pings is greater than the number Nm of messages, then during step 103 of analyzing the buffer, qualified useful messages are placed in the buffer memory.

[0134] If the number of pings Np is less than or equal to the number of messages Nm, the eligible useful message is not placed in the buffer memory and is sent as a useful message during the sending step (106-ENVut).

[0135] like Figure 4 As shown in FIG, method 100 further includes a step 104 of sorting the transmission of messages contained in buffer memory B. The messages contained in the buffer memory are sorted according to a parameter, which is the time difference between the maximum buffering time of the memory and the time at which method 100 is performed (which is the time for the onboard system 4 to receive the message). The time differences are sorted in ascending order. It is this order that determines the order in which the messages are processed, from the highest priority message (corresponding to the smallest time difference) to the lowest priority message (corresponding to the largest time difference).

[0136] Now refer to Figure 6 An example illustrating this second embodiment is described. In this example, the ping periods on channels C1, C2 and C3 are respectively: Tp1 = 2s, Tp2 = 4s, Tp3 = 8s.

[0137] As already indicated, the method 100 always maintains the temporal order of the pings. In this example, the sequence is as follows: Tp1, Tp2, Tp1, Tp3, Tp1, Tp2, etc. Figure 6 and summarized in the following table:

[0138] Next ping time Tp1 3s Tp2 4s Tp1 5s Tp3 6s Tp1 7s Tp2 8s Tp1 9s Tp1 11s Tp2 12s Tp1 13s Tp3 14s

[0139] Three messages will be considered, a first message Ma received by the onboard system 4 at T0 with a maximum buffer time Tba=8s, a second message Mb received at T0+2s with a maximum buffer time Tbb=10s, and a third message Mc received by the onboard system 4 at T0+3.5s with a maximum buffer time Tbc=5s.

[0140] At time T0 , the message Ma is received by the onboard system 4 .

[0141] If the number of useful messages in the buffer memory is less than the number of pings to be performed in the time interval Tba, the message Ma is placed in the buffer memory. In this case, the buffer memory is empty, so the message Ma is placed in the buffer memory, wherein its initial time Tba is equal to 8s.

[0142] At time T0+2s, the message Mb is received by the onboard system 4 .

[0143] If the number of useful messages in the buffer is less than the number of pings to be performed in the time interval Tbb, the message Mb is placed in the buffer. In this case, the buffer contains one message (Ma), and the number of pings to be performed within 10 seconds is 7. Therefore, the message Mb is placed in the buffer.

[0144] The buffer time of the message Ma at t0+2s is Tba(T0+2s)=8−2=6s, which is less than the maximum time Tbb of 10s. The message Mb is then placed in the second position after the message Ma in the buffer memory.

[0145] At T0+3s, a message Ma is sent over channel C1 instead of ping P1. It should be noted that Tbb(T0+3s)=9s. One second has passed since the buffering of the message Mb began.

[0146] At T0+3.5s, the message Mc is received by the onboard system 4 .

[0147] In the next 5 seconds, 2 pings are to be sent while the buffer contains a single message (Mb). Therefore, message Mc is placed in the buffer.

[0148] The buffer time of message Mb at T0+3.5s is Tbb(T0+3.5s)=10−3.5+2=10−1.5s=8.5s, which is greater than the maximum time Tbc of 5s. Therefore, message Mb is placed in the second position in the buffer memory, while message MC is placed in the first position.

[0149] The next ping arrives at T0+4s. The first message in the buffer is sent as a ping. This is message Mc, so it is delayed 0.5s before being sent at Tp2. Message Mb, originally scheduled to be sent at T0+4s (i.e., a 2-second delay), spends 3 seconds in the buffer. Therefore, it will be delayed by 3 seconds.

[0150] It should be noted that when a non-qualified useful message is sent over the utilized channel or the best channel, the timing of the channel "ping" period is reset (step 107) to the time at which the message was sent.

[0151] For example, when the priority channel is C3 and a non-qualified message arrives at T0, the sent non-qualified message acts as a ping and is not placed in the buffer memory. Since it is non-qualified, it is sent directly. Its transmission is still used as a measurement.

[0152] At this point (T0 in the example), look at the timing of the pings. Link C3 benefits from the measurement at T0. Given its ping period of Tp3 = 8 seconds, its next ping will occur at T0 + 8 seconds, then T0 + 16 seconds, then T0 + 24 seconds, and so on. The pings for the other channels remain unchanged. Therefore, as Tp3s slide towards the bottom of the list, the list for the next ping changes slightly. It should be noted that the system then checks that there are not too many messages in the buffer memory. If there are too many messages, the first message in the buffer is sent immediately.

[0153] It should be noted that, regardless of the embodiment, the number of ping messages required for the communication system 1 to function properly is reduced, which frees up bandwidth and reduces the energy to be supplied and the associated costs.

[0154] Figure 7An example of the internal architecture of an onboard system 4 of an aircraft 2 is schematically shown. As can be seen from this figure, the onboard system 4 comprises: a processor or CPU (Central Processing Unit) 1001; RAM (Random Access Memory) 1002; ROM (Read Only Memory) 1003; a storage unit (e.g., a hard disk (or a storage medium reader such as an SD (Secure Digital) card reader) 1004); and communication interfaces 1005, 1006, and 1007, which are configured to establish communication over communication channels C1, C2, and C3, respectively, connected via a communication bus 1000. The onboard communication system 4 also includes interfaces of the input / output port type, in particular for receiving signals from and sending signals to third-party equipment of the aircraft.

[0155] The processor 1001 is capable of executing instructions loaded into the RAM 1002 from the ROM 1003, an external memory (not shown), a storage medium (e.g., an SD card), or an attached communication network. When the onboard system 4 is powered on, the processor 1001 is capable of reading instructions from the RAM 1002 and executing them. These instructions form a computer program that causes the processor 1001 to implement the method 100.

[0156] The random access memory comprises at least one buffer memory, a respective memory for each channel C1 , C2 , C3 according to the first embodiment, and a memory common to the three channels C1 , C2 and C3 according to the second embodiment.

[0157] All or some of the methods implemented by the onboard system 4 or its described variants may be implemented in software by executing instruction sets using a programmable machine such as a DSP ("digital signal processor") or a microcontroller, or in hardware by a machine or dedicated component such as an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit). In general, the onboard system 4 comprises an electronic circuit system configured to implement the methods and sub-methods described in connection therewith, allowing communication to be established between the aircraft 2 and the remote station 3. Of course, the onboard communication system 4 also includes all the elements typically present in a system comprising a control unit and its peripherals, such as, in particular, power supply circuits, power supply monitoring circuits, one or more clock circuits, reset circuits, input / output ports, interrupt inputs, bus drivers, digital-to-analog and analog-to-digital converters (ideally fast converters), without this list being exhaustive.

[0158] Although the above implementation has been described and illustrated with reference to specific steps performed in a specific order, it should be understood that these steps may be combined, subdivided, or reordered without departing from the teachings of the present disclosure. At least some of the steps may be performed in parallel or serially. Therefore, the order and grouping of the steps do not constitute a limitation of the present invention.

[0159] For those skilled in the art, modifications and improvements to the implementation of the present invention described above may become obvious. The above description is by way of example and not by way of limitation. Therefore, the scope of the present invention is limited only by the scope of the appended claims.

Claims

1. A method (100) for selecting a communication channel, referred to as a utilized channel, from a plurality of communication channels (C1, C2, C3) between an onboard communication system (4) of an aircraft (2) and a communication station (3), referred to as a remote station (3), located at a distance from the aircraft (2), the method (100) comprising: - Step (S1): determining, for each of the communication channels (C1, C2, C3), one or more items of information representative of the transmission quality of messages between the onboard communication system (4) and the remote station (3), the messages being "useful" messages received by the onboard communication system (4) or being probe messages known as "ping" messages, wherein the useful messages are messages sent to the onboard communication system (4) by a source transmission application onboard the aircraft (2), wherein the ping messages are sent within a given period of time; - a step (S2) of classifying the communication channels (C1, C2, C3) based on the determined information according to an indicator respectively representative of the transmission quality determined for each of the communication channels (C1, C2, C3), wherein a single indicator is assigned to each communication channel; - Step (S3): selecting the utilization channel as the communication channel exhibiting the best transmission quality among the communication channels (C1, C2, C3) based on the indicator; The method further comprises: - Step (101): determining a buffer time called qualification time for each received useful message; and, if said qualification time is non-zero, - Step (102): Sending said useful message, called qualified useful message, instead of a ping message via said utilization channel.

2. The selection method according to claim 1, comprising a step (103) of analyzing the buffer of the qualified useful messages, including a check step (105, 106) depending on the state of the buffer memory and parameters related to the qualified useful messages.

3. The selection method according to the preceding claim, wherein the onboard communication system (4) comprises at least one buffer memory, wherein The step (103) of analyzing the buffer of qualified useful messages comprises the step (104) of determining a sequence for filling the at least one buffer memory.

4. Selection method according to the preceding claim, the onboard communication system (4) comprising a buffer memory dedicated to each communication channel (C1, C2, C3), wherein During the checking steps (105, 106), for the communication channels whose buffer memories are to be filled first according to the order obtained when the step (104) of determining the filling order is completed, if the buffer memories are empty and if the maximum message buffering time (Tbx) is greater than the duration (D) remaining until the next sending of the ping message, the qualified useful message is placed in the buffer memory during the step (103) of analyzing the buffer.

5. Selection method according to the preceding claim, wherein If the maximum message buffer time (Tbx) is less than or equal to the duration (D) remaining until the next transmission of a ping message, the eligible useful message is not placed in the buffer memory and is transmitted as a useful message during a transmission step (106).

6. The selection method according to claim 2 or 3, wherein the onboard communication system (4) comprises a buffer memory (B) shared by all the communication channels (C1, C2, C3), wherein: During a step of comparison between the state of the buffer memory and the parameters of the qualified useful message, the number of messages contained in the buffer memory (B), called the number of messages (Nm), is compared with the total number of ping messages, called the number of pings (Np), to be sent within a time equal to the maximum message buffering time (Tbx), and if the number of pings (Np) is greater than the number of messages (Nm), the qualified useful message is placed in the buffer memory during a step of analyzing the buffer (103).

7. Selection method according to the preceding claim, wherein If the number of pings (Np) is less than or equal to the number of messages (Nm), the qualified useful message is not placed in the buffer memory and is sent as a useful message during a sending step (106).

8. An onboard communication system (4) intended to equip an aircraft (2), said onboard communication system (4) being configured to establish communication with a remote communication station (3) via a communication channel (C1, C2, C3) called "optimal channel" among a plurality of communication channels (C1, C2, C3), wherein The onboard communication system (4) is configured to implement the following steps: - step (S1): determining, for each of the communication channels (C1, C2, C3), one or more items of information representative of the transmission quality of messages between the aircraft (2) and the remote station (3), the messages being "useful" messages received by the onboard communication system (4) or being probe messages known as "ping" messages, wherein the useful messages are messages sent to the onboard communication system (4) by a source transmission application onboard the aircraft (2), wherein the ping messages are sent within a given period of time; - a step (S2) of classifying the communication channels (C1, C2, C3) based on the determined information according to an indicator respectively representing the end-to-end transmission quality determined for each of the communication channels (C1, C2, C3), wherein a single indicator is assigned to each communication channel; - Step (S3): selecting the utilization channel as the communication channel exhibiting the best transmission quality among the communication channels (C1, C2, C3) based on the indicator; - Step (101): determining a buffer time called qualification time for each received useful message; and, if said qualification time is non-zero, - Step (102): Sending said useful message, called qualified useful message, instead of a ping message.

9. An aircraft (2) comprising an on-board communication system (4) according to the preceding claim.

10. A computer-readable medium comprising instructions for executing the method according to any one of claims 1 to 7.

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