A computer implemented method in a transmitter for transmitting information carried by a signal over a channel to a receiver, wherein signal processing by the transmitter and by the receiver is degraded by one or more hardware impairments, the method comprising receiving feedback data indicating contextual information of the hardware impairments, selecting a signal format for use in generating the signal based on a mapping between the contextual information of the hardware impairments and a pre-determined set of signal formats, generating the signal based on the information and on the selected signal format, and transmitting the signal to the receiver.