METHOD AND DEVICE FOR TRANSMITTING A MESSAGE

Description

TECHNICAL FIELD

[0001] At least one embodiment relates to a method of transmitting a message from a first node device to a second node device belonging to a neighborhood of the first node device, said first and second node devices belonging to a hybrid RF power line communication network. At least one embodiment relates to a device implementing the method. STATE OF PRIOR ART

[0002] Powerline communications (PLC) are developing, particularly in the context of AMM (Automated Meter Management) power supply networks. Communication networks are thus implemented in power supply networks for the automated collection by a basic node device (also called a "data concentrator") of the network, from smart electricity meters, of energy consumption reading data that said smart electricity meters are respectively responsible for monitoring.

[0003] The G3-PLC communication standard is defined to allow the various node devices (including data concentrators and smart electricity meters) of such a network to communicate with each other. The standard is specified in the ITU-T G.9903 recommendation, which describes in particular the physical layer (PHY) and the data link layer (DLL) of the OSI model (acronym for "Open Systems Interconnection"). The G3-PLC standard is intended to be used in frequency bands ranging from 10 to 490 kHz. It supports the following frequency bands in particular: the CENELEC A frequency band, which ranges from approximately 35 kHz to 91 kHz; the FCC frequency band, which ranges from approximately 150 kHz to 480 kHz; the ARIB frequency band, which ranges from approximately 150 kHz to 400 kHz; and the CENELEC B frequency band, which ranges from approximately 98 kHz to 122 kHz.These different frequency bands have different characteristics in terms of flow rate, range, and resistance to interference, in particular.

[0004] In an evolution of the G3-PLC standard defined in Annex H of the ITU-T recommendation G.9903 (2017) Amendment 1 (05 / 2021), called G3-PLC Hybrid PLC & RF, an RF radio channel (acronym for radio frequency) can be used instead of one of the said PLC frequency bands. More precisely, this version of the standard allows the occasional use of a secondary radio physical layer based on SUN FSK modulation as defined in the IEEE 802.15.4:2015 standard. Thus, by using the different G3-PLC and RF media to transmit data, the power supply network maximizes its coverage and resilience. A power supply network node capable of transmitting and receiving data using both media (PLC and RF) is called a hybrid node.

[0005] However, in G3-PLC Hybrid PLC & RF, the choice of communicating between two hybrid nodes in the communication network using either a PLC frequency band or an RF radio channel is determined at the time of construction or reconstruction of the communication routes.

[0006] For example, discovery messages (beacon request in English) or broadcast messages (broadcast frame in English) are sent by a hybrid node simultaneously on both PLC and RF media while messages intended for a single node (unicast frame in English) are only transmitted on one of the two media and the acknowledgment of messages intended for a single node is only carried out on the media on which the message was received.

[0007] This choice of communication medium used between two hybrid network nodes is generally fixed for several hours. The G3-PLC Hybrid PLC & RF standard defined in Amendment 1 (05 / 2021) therefore does not allow the full flexibility offered by PLC / RF hybridization to be used.

[0008] It is desirable to overcome these various drawbacks of the state of the art. In particular, it is desirable to propose a communication method which allows the dynamic use of both communication media, in this case at least one frequency band of the power supply network using power line communications and a radio channel.

[0009] US patent application 2012 134395 A1 discloses power line communications over different voltage ranges using multiple frequency sub-bands. STATEMENT OF THE INVENTION

[0010] To this end, according to a first aspect, the invention proposes a method for transmitting a message from a first node device to a second node device belonging to a neighborhood of said first node device, said first and second node devices belonging to an electrical power supply network using power line carrier communications, characterized in that the first node device is capable of transmitting and receiving fragments of the message on at least one frequency band of the electrical power supply network using power line carrier communications and on a radio channel and in that the method is executed by the first node device and comprises the steps, prior to the transmission of the fragment, of: estimation, for the radio channel, of the theoretical transmission duration of the fragment on the radio channel, estimation of a cumulative utilization rate, by the node device, of the radio channel considering that the fragment is transmitted on the radio channel and if the estimated utilization rate is lower than a maximum utilization threshold, the method comprises the steps of: estimation, for the at least one frequency band, of the theoretical transmission duration of the fragment on the at least one frequency band, obtaining a database, of the result of integration of the occupancy rate of the at least one frequency band determined over several time scales corresponding to the theoretical transmission duration of the fragment on the at least one frequency band, obtaining from the database, of the result of integration of the occupancy rate of the radio channel determined over several time scales corresponding to the theoretical transmission duration of the fragment on the at least one frequency band,selection from the rate integration results of the at least one frequency band or the radio channel, transmission of the fragment on the at least one frequency band or on the radio channel depending on the selection.

[0011] The invention also relates to a device for transmitting a message from a first node device to a second node device belonging to a neighborhood of said first node device, said first and second node devices belonging to an electrical power supply network using power line carrier communications, characterized in that the first node device is capable of transmitting and receiving fragments of the message on at least one frequency band of the electrical power supply network using power line carrier communications and on a radio channel and in that the first node device activates prior to the transmission of the fragment: means for estimating, for the radio channel, the theoretical transmission duration of the fragment on the radio channel, means for estimating a cumulative utilization rate, by the node device, of the radio channel considering that the fragment is transmitted on the radio channel and if the estimated utilization rate is lower than a maximum utilization threshold, the first node device activates: means for estimating, for the at least one frequency band, the theoretical transmission duration of the fragment on the at least one frequency band, means for obtaining a database, the result of integrating the occupancy rate of the at least one frequency band determined over several time scales corresponding to the theoretical transmission duration of the fragment on the at least one frequency band, means for obtaining the database,of the result of integration of the occupancy rate of the radio channel determined over several time scales corresponding to the theoretical transmission duration of the fragment on the radio channel, means of selection from the results of integration of the rate of the at least one frequency band or of the radio channel, means of transmission of the fragment on the at least one frequency band or on the radio channel depending on the selection.

[0012] Thus, the present invention makes it possible to benefit from the advantages, in terms of flow rate, range, resistance to interference, of at least one frequency band or radio channel.

[0013] Furthermore, by determining occupancy rates of at least one frequency band and the radio channel over several time scales, it is possible to take into account and anticipate cyclical variations in the occupancy of the communication network. Cyclical variations in the occupancy of the communication network are linked, for example, to cyclical interrogations by a concentrator to obtain meter load curves. These interrogations can be carried out according to an hourly, daily or other periodicity.

[0014] According to a particular embodiment of the invention, if the estimated utilization rate is not less than a maximum utilization threshold, the method comprises the step of transmitting the fragment on the frequency band.

[0015] According to a particular embodiment of the invention, the results of integration of the occupancy rate of the or each frequency band and of the radio channel are determined over three time scales, a second time scale being greater than a first time scale and less than a third time scale.

[0016] According to a particular embodiment of the invention, the first time scale is the minute, the second time scale is the hour, the third time scale is the day.

[0017] According to a particular embodiment of the invention, the database stores results of integration of occupancy rates of the at least one frequency band and of the radio channel determined during the first time scale over a period of one hour, stores results of integration of occupancy rates of the at least one frequency band and of the radio channel determined during the second time scale over a period of twenty-four hours and stores results of integration of occupancy rates of the at least one frequency band and of the radio channel determined during the third time scale over a period of one week.

[0018] According to a particular embodiment of the invention, the at least one frequency band is part of a set of frequency bands comprising: the CENELEC A frequency band; the CENELEC B frequency band; and the FCC frequency band or the ARIB frequency band.

[0019] The present invention also relates to a computer program product. It comprises instructions for implementing, by a node device, the method according to one of the preceding embodiments, when said program is executed by a processor of the node device.

[0020] The present invention also relates to a storage medium. It stores a computer program comprising instructions for implementing, by a node device, the method according to one of the preceding embodiments, when said program is executed by a processor of the node device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above-mentioned and other features of the invention will become more clearly apparent from the following description of an exemplary embodiment, said description being given in relation to the accompanying drawings, among which: [ Fig. 1 ] schematically illustrates a communication network according to one embodiment; [ Fig. 2 ] schematically illustrates the different layers of an OSI model in the particular case of the G3-PLC Hybrid PLC & RF standard; [ Fig. 3 ] schematically illustrates a method for generating and updating a database for at least one frequency band or for the radio channel of the communication network according to the present invention; [ Fig. 4 ] schematically illustrates a method for selecting at least one frequency band or radio channel of the communication network for the transmission of a message according to the present invention; [ Fig. 5 ] schematically illustrates an example of hardware architecture of a node device of the communication network according to one embodiment. DETAILED PRESENTATION OF IMPLEMENTATION METHODS

[0022] There Fig. 1 schematically illustrates a mesh communication network 120. The mesh communication network 120 is for example an AMM type electrical power supply network. The mesh communication network 120 relies on PLC power line communications or RF radio frequencies to allow a base node device (also called a “data concentrator”) to collect, from smart electricity meters, energy consumption reading data from electrical installations that said smart electricity meters are respectively responsible for monitoring. The data concentrator and the smart electricity meters are thus node devices of the mesh communication network 120. The mesh communication network 120 may include other node devices, for example installed at electrical transformers.The communication network 120 therefore has a mesh structure, as shown schematically in the . Fig. 1 using the arrows, where node devices act as relays to increase the range of communications in the mesh communication network 120, as detailed below. Thus, a single smart electricity meter potentially has multiple paths to reach the data concentrator, and vice versa. In the remainder of the document, the terms “smart electricity meter” and “meter” are used interchangeably.

[0023] The present invention is thus particularly suited to the context of G3-PLC Hybrid PLC & RF technology as defined in recommendation ITU-T G.9903 (2017) Amendment 1 (05 / 2021) and more particularly in Annex H.

[0024] The mesh communication network 120 thus comprises a plurality of node devices 130, 131, 132, 133, 134, 135, 136, 137, 138, 139. Each node device of the mesh communication network 120 is associated with a network neighborhood. On the Fig. 1 , the node device 133 is associated with a network neighborhood 110 encompassing the node devices 130, 134 and 137. Indeed, in the mesh communication network 120, a signal or a message broadcast by a node device (such as the node device 133) is generally not visible at every point of said communication network. Each node device transmitting signals or messages then has a network neighborhood, that is to say a subset of said mesh communication network 120 in which any node device can intelligibly receive said signals or messages directly from the node device having broadcast said signals or messages. The network neighborhood corresponds to the range of the signals transmitted, according to predetermined transmission parameters (e.g. power, modulation and coding scheme, network topology, etc.)) of the node device at the source of said signals and also potentially depending on characteristics of the communication channel (attenuation, noise, impedance, etc.).

[0025] The mesh communication network 120 is based on a reactive routing protocol, such as the LOADng protocol (Lightweight On-demand Ad hoc Distance-vector Routing Protocol - Next Generation). Unlike proactive routing protocols that rely on global knowledge of network topology, reactive routing protocols rely on on-demand route discovery, each node device of the network then only needs to be aware of its own network neighborhood to route data in the mesh communication network 120.

[0026] In terms of frequency bands that can be used in the implementation of the mesh communication network 120, we can cite: the CENELEC A frequency band, which ranges from approximately 35 kHz to 91 kHz; the FCC frequency band, which ranges from approximately 150 kHz to 480 kHz; the ARIB frequency band, which ranges from approximately 150 kHz to 400 kHz; the CENELEC B frequency band, which ranges from approximately 98 kHz to 122 kHz and the RF radio channel which ranges from approximately 863 MHz to 870 MHz.It is then possible to use: a first modulation scheme with thirty-six carriers in the CENELEC A frequency band; a second modulation scheme with seventy-two carriers in the FCC frequency band; a third modulation scheme with fifty-four carriers in the ARIB frequency band; a fourth modulation scheme with sixteen carriers in the CENELEC B frequency band and a fifth modulation scheme of the SUN-FSK type for the RF radio channel of G3-PLC Hybrid PLC & RF. The SUN-FSK modulation is defined in section 20 of the IEEE 802.15.4:2015 document.

[0027] There Fig. 2 schematically illustrates the different layers of an OSI model in the particular case of the G3-PLC Hybrid PLC & RF standard as defined in Annex H of Recommendation ITU-T G.9903 (2017) Amendment 1 (05 / 2021).

[0028] A message to be transmitted from an application layer 200 is transmitted to a transport layer 201. The transport layer 201 groups together all the protocols responsible for error management and network flow control. The two main protocols used are TCP and UDP. The transport layer 201 creates packets by adding headers to the data coming from the application layer 200. The packets are then transmitted to the IP layer, e.g. IPv6 202. The IP layer 202 encapsulates the packets coming from the transport layer 201 by adding, in particular, an IPv6 header. An IPv6 packet can be up to 1400 bytes. In the case where the packet is larger than a threshold value, this packet is fragmented into at least two fragments in order to adapt it to the constraints of the MAC layer (acronym for "Media Access Control"), in particular the size of the MAC frames.

[0029] To this end, the G3-PLC Hybrid PLC & RF standard incorporates the 6LoWPAN protocol, which allows IPv6 data packets to be adapted to the constraints of the MAC layers, in particular by fragmenting them. Indeed, the MAC frames used are much smaller (maximum 400 bytes available per packet for the IP part) than the 1,400-byte IPv6 packets.

[0030] IPv6 packets are passed to an adaptation sublayer 203a which incorporates the 6LoWPAN protocol which fragments them if necessary. Of course, in the case of an IPv6 packet small enough to be contained in a single G3-PLC MAC or RF MAC frame, no fragmentation is performed.

[0031] A hybrid abstraction layer 203b then forwards the fragment or IP packet in the absence of fragmentation to the appropriate MAC sublayer 204a or 204b, depending on the medium chosen for its transmission.

[0032] In the following, the term fragment is used to refer to both a fragment obtained from a fragmented IP packet or the IP packet itself in the absence of fragmentation.

[0033] The transmission of a fragment on the PLC medium, i.e. on the power line, typically includes different steps, including segmentation of the fragments to adapt them to the G3-PLC PHY 205a physical layer and OFDM modulation of the signal. Segmentation consists of partitioning a MAC frame into PSDUs (acronym for "PHY Service Data Unit"). All PSDUs from the same fragment are modulated using the same modulation scheme.

[0034] The transmission of a fragment on the RF radio channel includes different steps, including segmentation of the fragments to adapt them to the RF radio physical layer PHY 205b and SUN-FSK modulation of the signal. As in the PLC case, segmentation consists of partitioning a MAC (Media Access Control) frame into PSDUs (PHY Service Data Unit). All PSDUs from the same fragment are modulated using the same modulation scheme. The specification of the RF radio physical layer PHY 205b is given in sections 10, 11 and 20 of the IEEE 802.15.4-2015 standard as modified by the IEEE 802.15.4v:2017 document and supplemented by Table H-5-1 of the ITU-T recommendation G.9903 (2017) Amendment 1 (05 / 2021).

[0035] It should be noted that the G3-PLC Hybrid PLC & RF standard defined in Table H.6.8 of Annex H imposes constraints on the usage time, over a sliding time window, of the RF radio channel by each node device. For this purpose, three predetermined values and a rate are defined: macDutyCyclePeriod_RF: a first predetermined value that defines a duration of a sliding time window in seconds (for example: 3600), macDutyCycleLimit_RF: a second predetermined value that defines an absolute limit of authorized usage time on the sliding time window in seconds (for example: 90 for the meters and 360 for the data concentrator), macDutyCycleThreshold_RF: a third predetermined value that defines, for each meter and each concentrator, a maximum threshold of authorized usage time before interrupting any RF transmission, expressed in percents (for example: 90, which means that transmissions are stopped when 90% of 90 seconds are reached over the last 3600 seconds for the meters, or 90% of 360 seconds over the last 3600 seconds for the data concentrator), macDutyCycleUsage_RF: a transmission usage rate per radio frequencies.This utilization rate is calculated over the sliding window relative to the second predetermined value, i.e. macDutyCycleLimit_RF. ITU-T Recommendation G.9903 (2017) Amendment 1 (05 / 2021) states in table H.6.8 that macDutyCycleUsage_RF = tps / macDutyCycleLimit_RF*100 where tps is the current time of use of the radio-frequency transmission accumulated over the sliding time window by the node device.

[0036] In order to use all the flexibility offered by PLC / RF hybridization, the communication methods described with reference to Figs. 3 And 4 are implemented to distribute the fragments provided by the adaptation sublayer between the two RF MAC and PLC MAC layers in an optimal manner. More precisely, the described methods are implemented at the hybrid abstraction layer.

[0037] There Fig. 3 schematically illustrates a method for generating and updating a database for at least one frequency band or for the radio channel of the communication network according to the present invention.

[0038] The method is executed continuously by each node device which is capable of transmitting and receiving messages on at least one frequency band and the radio channel of the communication network.

[0039] The at least one frequency band is selected from the set of frequency bands authorized by G3-PLC, ie CENELEC A, CENELEC B, and ARIB or FCC. In a particular embodiment, the method is executed continuously for several frequency bands of the set of frequency bands by G3-PLC, ie CENELEC A, CENELEC B, and ARIB or FCC.

[0040] In step E30, the node device determines the occupancy rate of a frequency band or of the radio channel. The occupancy rate of a G3-PLC frequency band is for example determined by using the mechanism used in the listening method of a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) medium. The mechanism makes it possible to check at any time whether the frequency band is occupied or not. The occupancy rate is calculated by measuring the occupation time of the frequency band during the time window.

[0041] The radio channel occupancy rate is determined, for example, by measuring the radio channel occupancy time during the time window.

[0042] For example, the time window is equal to one minute and the occupancy rate indicates, for the minute, the number of seconds during which the frequency band or radio channel is occupied.

[0043] In step E31, the node device integrates the occupancy rates determined during a first time scale. The first time scale is for example equal to one minute. For example, the node device calculates the average of the sixty occupancy rates determined during the minute.

[0044] The result of the integration is then stored in step E34 in a database in association with a time marker.

[0045] The database contains a first given number of integration results during the first time scale over a first duration. For example, the first duration is equal to one hour and the first given number is equal to sixty.

[0046] For example, the first duration is equal to twenty-four hours and the first number given is equal to one thousand four hundred.

[0047] In step E32, the node device integrates the occupancy rates determined during a second time scale. The second time scale is greater than the first time scale. The second time scale is, for example, equal to one hour. For example, the node device calculates the average of the three thousand six hundred occupancy rates determined during the hour.

[0048] The result of the integration is then stored in step E34 in a database in association with a timestamp.

[0049] The database contains a second given number of integration results during the second timescale over a second duration. For example, the second duration is equal to twenty-four hours and the second given number is equal to twenty-four. For example, the second duration is equal to twenty-four hours and the second given number is equal to one hundred and sixty-eight.

[0050] In step E33, the node device integrates the occupancy rates determined over a third time scale. The third time scale is greater than the second time scale. The third time scale is, for example, equal to twenty-four hours. For example, the node device calculates the average of the two hundred and sixteen thousand occupancy rates determined over twenty-four hours.

[0051] The result of the integration is then stored in step E34 in a database in association with a time marker.

[0052] The database has a third given number of integration results during the third timescale over a third duration. For example, the third duration is equal to seven days and the third given number is equal to seven.

[0053] For example, the third duration is equal to seven days and the third given number is equal to twenty-eight.

[0054] There Fig. 4 schematically illustrates a method for selecting at least one frequency band or radio channel of the communication network for the transmission of a message according to the present invention.

[0055] The method is executed each time a message is sent by each node device which is capable of transmitting and receiving messages on at least one frequency band and on the radio channel of the communication network.

[0056] The associated frequency bands are for example selected from the set of frequency bands authorized by G3-PLC, i.e. CENELEC A, CENELEC B, and ARIB or FCC.

[0057] At step E400, the node device has a fragment to send over the communication network.

[0058] In step E401, the node device obtains the theoretical throughput of the radio channel.

[0059] In step E402, the node device estimates, for the radio channel, the theoretical transmission duration of the fragment on the radio channel.

[0060] In step E403, the node device estimates the cumulative utilization rate, by the node device, of the RF radio channel in percent considering that the fragment is transmitted on the radio channel.

[0061] In step E404, the node device checks whether the estimated usage rate macDutyCycleUsage_RF is less than the third predetermined value macDutyCycleThreshold_RF.

[0062] If yes, the node device proceeds to step E406. If no, the node device proceeds to step E405.

[0063] In step E405, the node device prohibits the selection of the radio channel for the transmission of the fragment and proceeds to step E406.

[0064] In step E406, the node device obtains the theoretical throughput of one or more frequency bands on which the node device is able to transmit and receive messages.

[0065] As mentioned previously, each frequency band has, for each type of modulation used on the frequency band, a given theoretical throughput. The node device obtains the theoretical throughput of the or each frequency band on which the node device is able to transmit and receive messages corresponding to the modulation used for sending the fragment to the node to which the fragment is to be transferred.

[0066] In step E407, the node device estimates, for the or each frequency band, the theoretical emission duration of the fragment on the or each frequency band.

[0067] In step E408, the node device queries the database to obtain the integration results corresponding to the theoretical transmission duration of the fragment in each frequency band and on the radio channel if the selection of the radio channel is not prohibited. Thus, the node device obtains, for the radio channel if the selection of the radio channel is not prohibited and for the or each frequency band, the number of integration results during the first time scale corresponding to the theoretical transmission duration of the fragment in the frequency band and in the radio channel if the selection of the radio channel is not prohibited. The node device obtains the number of integration results during the second time scale corresponding to the time at which the fragment must be sent. The node device obtains the number of integration results during the third time scale corresponding to the day on which the fragment must be sent.

[0068] In step E409, the node device selects the frequency band or the frequency band among the frequency bands or the radio channel if the selection of the radio channel is not prohibited for which the integration results are the lowest. For example, the node device calculates for the or each frequency band and for the radio channel if the selection of the radio channel is not prohibited, the average of the integration results during the first, second and third time scales and selects the frequency band for which the calculated average is the lowest.

[0069] Alternatively, a weight is assigned to the results of integrations during the first, second, and third time scales before averaging.

[0070] For example, a weight of 10 is assigned to the results of integrations during the first time scale, a weight of 12 is assigned to the results of integrations during the second time scale, and a weight of 7 is assigned to the results of integrations during the third time scale.

[0071] In step E410, the node device transfers the fragment to the selected frequency band or to the radio channel if the radio channel has been selected.

[0072] It should be noted here that if the node device is able to transmit and / or receive messages on a single frequency band and the selection of the radio channel is prohibited, the node device does not execute steps E406 to E409 and transfers the fragment to the frequency band where it is able to transmit and / or receive messages.

[0073] There Fig. 5 schematically illustrates an example of hardware architecture of a node device of the communication network according to one embodiment.

[0074] Such a node device is called multi-band because it is capable of transmitting a message on several frequency bands. Note that the Fig. 5 could also schematically illustrate an example of hardware architecture of a processing module included in the node device.

[0075] According to the hardware architecture example shown in Fig. 5 , the node device 130 then comprises, connected by a communication bus 1300: a processor or CPU (“Central Processing Unit” in English) 1301; a RAM (“Random Access Memory” in English) 1302; a ROM (“Read Only Memory” in English) 1303; a storage unit such as a hard disk (or a storage media reader, such as an SD (“Secure Digital” in English) card reader) 1304; at least one communication interface 1305 allowing the node device 130 to communicate with the node devices belonging to its neighborhood, eg the nodes 131 and 133.

[0076] The processor 1301 is capable of executing instructions loaded into the RAM 1302 from the ROM 1303, an external memory (not shown), a storage medium (such as an SD card), or a communications network. When the node device is powered on, the processor 1301 is capable of reading instructions from the RAM 1302 and executing them. These instructions form a computer program causing the processor 1301 to implement some or all of the methods described in connection with the Figs. 3 And 4 .

[0077] The methods described below in relation to the Figs. 3 And 4can be implemented in software form by executing a set of instructions by a programmable machine, for example a DSP (Digital Signal Processor) or a microcontroller, or be implemented in hardware form by a machine or a dedicated component, for example an FPGA (Field-Programmable Gate Array) or an ASIC (Application-Specific Integrated Circuit). In general, the node device 130 comprises electronic circuitry configured to implement the methods described in relation to the Figs. 3 And 4 .

Claims

1. Method for transmitting a message from a first node device to a second node device belonging to a neighbourhood of said first node device, said first and second node devices belonging to an electrical supply network using powerline communications, characterised in that the first node device is able to send and receive fragments of the message on at least one frequency band of the electrical supply network using powerline communications and over a radio channel and in that the method is executed by the first node device and comprises the steps, prior to the transmission of the fragment, of: - estimating (E402), for the radio channel, the theoretical duration of transmission of the fragment over the radio channel, - estimating (E403) a total degree of use, by the node device, of the radio channel while considering that the fragment is transmitted over the radio channel and, if the degree of use estimated is below a maximum use threshold, the method comprising the steps of: - estimating (E407), for the at least one frequency band, the theoretical duration of transmission of the fragment on the at least one frequency band, - obtaining (E408), from a database, the result of integration of the degree of occupation of the at least one frequency band determined during several timescales corresponding to the theoretical duration of transmission of the fragment on the at least one frequency band, - obtaining (E408), from the database, the result of integration of the degree of occupation of the radio channel determined during several timescales corresponding to the theoretical duration of transmission of the fragment over the radio channel, - selecting (E409), from the results of integration of the degree, the at least one frequency band or the radio channel, - transmitting (E410) the fragment on the at least one frequency band or over the radio channel according to the selection.

2. Method according to claim 1, characterised in that, if the degree of use estimated is not below a maximum use threshold, the method comprises the step of transmitting the fragment on the frequency band.

3. Method according to claim 1 or 2, characterised in that the results of integration of the degree of occupation of the or each frequency band and of the radio channel are determined during three timescales, a second timescale being longer than a first timescale and shorter than a third timescale.

4. Method according to claim 3, characterised in that the first timescale is the minute, the second timescale is the hour, and the third timescale is the day.

5. Method according to claim 3 or 4, characterised in that the database stores results of integration of the degree of occupation of the at least one frequency band and of the radio channel determined during the first timescale over a period of one hour, stores results of integration of the degree of occupation of the at least one frequency band and of the radio channel determined during the second timescale over a period of twenty-four hours, and stores results of integration of the degree of occupation of the at least one frequency band and of the radio channel determined during the third timescale over a period of one week.

6. Method according to any one of claims 1 to 5, characterised in that the at least one frequency band forms part of a set of frequency bands comprising: - the CENELEC A frequency band; - the CENELEC B frequency band; and - the FCC frequency band or the ARIB frequency band.

7. Device for transmitting a message from a first node device to a second node device belonging to a neighbourhood of said first node device, said first and second node devices belonging to an electrical supply network using powerline communications, characterised in that the first node device is able to send and receive fragments of the message on at least one frequency band of the electrical supply network using powerline communications and over a radio channel, and in that the first node device, prior to the transmission of the fragment, activates: - means (1301) for estimating, for the radio channel, the theoretical duration of transmission of the fragment over the radio channel, - means (1301) for estimating a total degree of use, by the node device, of the radio channel while considering that the fragment is transmitted over the radio channel and, if the degree of use estimated is below a maximum use threshold, the first node device activates: - means (1301) for estimating, for the at least one frequency band, the theoretical duration of transmission of the fragment on the at least one frequency band, - means (1301) for obtaining, from a database, the result of integration of the degree of occupation of the at least one frequency band determined during several timescales corresponding to the theoretical duration of transmission of the fragment on the at least one frequency band, - means (1301) for obtaining, from the database, the result of integration of the degree of occupation of the radio channel determined during several timescales corresponding to the theoretical duration of transmission of the fragment over the radio channel, - means (1301) for selecting, from the results of integration of the degree, the at least one frequency band or the radio channel, - means (1301) for transmitting the fragment on the at least one frequency band or over the radio channel according to the selection.

8. A computer program product, characterised in that it comprises instructions for implementing, by a node device (130), the method according to any one of claims 1 to 6, when said program is executed by a processor of the node device.

9. A storage medium, characterised in that it stores a computer program comprising instructions for implementing, by a node device (130), the method according to any one of claims 1 to 6, when said program is executed by a processor of the node device.