1. A method for multiple access to a frequency band of a communication channel of a communication network with carrier sense and collision avoidance, said frequency band being divided into a set of sub-bands of the communication channel, the method comprising at a source node: detecting the availability of the communication channel; subsequent to detecting the availability of the communication channel, modifying a value of a backoff counter; and when the value of the backoff counter reaches a predetermined value, transmitting a destination node of a message requesting authorisation to send data on the communication channel, wherein said transmitting is performed on one or more sub-bands forming a sub-set of said set of sub-bands of the communication channel.