A method of channel selection in a wireless network, the method being performed at a first communications node i and comprising: (a) identifying a plurality of communications channels q n and, for each channel: determining a first interference measure U i S for the channel based on received energy or power from one or more other nodes j (104, 106) using said channel; and (b) selecting a channel from the plurality of communications channels q n characterised by: for each identified channel: (i) transmitting from the node i a modulated pulse of power P i effective to cause the or each other node j (104, 106) using said channel to issue a modulated echo pulse of power P j in reply; (ii) causing the or each other node j (104, 106) using said channel to transmit an echo signal in response to the transmitted modulated pulse of power P i; and receiving the echo signal(s) at the first communications node i; (iii) determining from the or each echo signal a second interference measure U i A representative of the interference that node i will cause on the node j (104, 106); (iv) determining a third interference measure U i based on a combination of the first and second interference measures; and wherein the selecting step comprises selecting a channel whose third interference measure meets a predetermined condition. (a) identifying a plurality of communications channels q n and, for each channel: determining a first interference measure U i S for the channel based on received energy or power from one or more other nodes j (104, 106) using said channel; and (b) selecting a channel from the plurality of communications channels q n characterised by: for each identified channel: (i) transmitting from the node i a modulated pulse of power P i effective to cause the or each other node j (104, 106) using said channel to issue a modulated echo pulse of power P j in reply; (ii) causing the or each other node j (104, 106) using said channel to transmit an echo signal in response to the transmitted modulated pulse of power P i; and receiving the echo signal(s) at the first communications node i; (iii) determining from the or each echo signal a second interference measure U i A representative of the interference that node i will cause on the node j (104, 106); (iv) determining a third interference measure U i based on a combination of the first and second interference measures; and wherein the selecting step comprises selecting a channel whose third interference measure meets a predetermined condition. (i) transmitting from the node i a modulated pulse of power P i effective to cause the or each other node j (104, 106) using said channel to issue a modulated echo pulse of power P j in reply; (ii) causing the or each other node j (104, 106) using said channel to transmit an echo signal in response to the transmitted modulated pulse of power P i; and receiving the echo signal(s) at the first communications node i; (iii) determining from the or each echo signal a second interference measure U i A representative of the interference that node i will cause on the node j (104, 106); (iv) determining a third interference measure U i based on a combination of the first and second interference measures; and