Method and device for transmitting a message

A 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, wherein 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 the first node device comprises circuitry causing the first node device, prior to the transmission of the fragment, to perform:

• estimating, for the radio channel, the theoretical duration of transmission of the fragment over the radio channel,
• estimating a cumulative 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 comprises the steps of:
• estimating, for the at least one frequency band, the theoretical duration of transmission of the fragment on the at least one frequency band,
• 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,
• 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,
• selecting, from the results of integration of the degree, the at least one frequency band or the radio channel,
• transmitting the fragment on the at least one frequency band or over the radio channel according to the selection.