A method of transmitting an amplitude shift keying signal comprises determining timing of an Orthogonal Frequency Division Multiplex, OFDM, transmission of a concurrently operating transmission system, wherein the OFDM transmission applies an extended representation for at least a part of the transmitted OFDM transmission, which extended representation comprises an extended part, representing a data signal to be transmitted by amplitude shift keying, and transmitting the amplitude shift keyed data signal intermittently aligned with the OFDM transmission such that symbols of the amplitude shift keyed data signal occurs only during the extended part of the OFDM transmission. The data signal may represent a wake-up signal arranged to address a wake-up radio. A transmitter, network node and computer program for implementing the method are also disclosed.