A communication device arranged to communicate data with another device at a given time instant according to either a first communication protocol or a second communication protocol, the communication device being constrained to transmit data according to the first communication protocol during a transmission window of predetermined duration that commences at a predetermined time instant and being arranged to, in dependence on a data communication according to the second communication protocol to be made by the communication device during that transmission window, select a time instant in that same transmission window for commencing a data transmission according to the first communication protocol.