A transmission method is used by a node of a communications network, wherein nodes communicate with one another via a carrier-sense multiple-access channel, said method comprising a step of sending a signal at a given transmit power and a given data rate to a receiver node over the channel, and wherein the transmit power of the sent signal assumes successively a first power value during a first time period and then a second power value during a second time period, the two power values being different and one of them being equal to the given power, the first time period representing the given power and the second time period representing the data rate. The invention also relates to a method of receiving a signal sent by the transmission method enabling the transmit power and the data rate used by the sender node to be deduced from the received signal.