Abstract: Control of communication in a data communication system of at least two subsystems is presented. Scheduling transfer of data is performed from a transmitting subsystem to a receiving subsystem. The scheduling comprises determining at least one of a plurality of transfer conditions including a level of activity of each subsystem, a point in time when each subsystem is scheduled to be active, a time limit for receiving data, in the receiving subsystem, an amount of data the receiving subsystem need, and a maximum amount of outstanding data in transfer between said subsystem. In dependence on at least the determined transferring conditions is transferring of data from the transmitting subsystem to the receiving subsystem, the transfer being subject to a delay that depends on the determined at least one transfer condition.