Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for transmitting data. In one aspect, a method obtains a baseline data rate for transmissions from a node that are received over a channel of a power line communications system and a set of available modulation techniques for the node. The set of available modulation techniques can include at least two modulation techniques with which the node is configured to encode data that are transmitted over the channel. Using the set of available modulation techniques, a modulation technique that is capable of providing at least the baseline data rate with at least a threshold confidence for the node is selected. In turn, data is provided to the node specifying the selected modulation technique.