The present invention relates to a method for determining an operational channel c_op of a communication network comprising at least two potential proxies for an energy-restricted device to join the network, and a set C of radio channels, wherein an energy-restricted device is to join the network, the method comprising the following steps: —the energy-restricted device transmitting a first beacon message on a first channel succ(m−1)(c) in MAC broadcast, wherein c belongs to the set C, and switching to receiving mode on channel listen(c), wherein succ and listen is an arithmetical function, from C to C, and m is a positive integer, —the proxies receiving the beacon message sent on channel succ(m−1)(c), —the temporary master device switching its radio receiver to channel succm(c), —the energy-restricted device transmitting a second beacon message on a second channel succ(c) and switching to receiving mode on channel listen (succm(c)), —upon receipt of the second beacon, the temporary master device transmitting a response on a channel listen listen(succm(c)), 20 —the energy-restricted device receiving the beacon response on a channel listen listen(succm(c)), determining that c=c_op. The invention also relates to an energy-restricted device and a proxy device therefor.