A method and apparatus for data transmission between a transmitter-side data transmission unit and a receiver-side data transmission unit is provided. The method includes transmitting a first portion of a data packet from a real-time application to the receiver-side data transmission unit, receiving a communication channel availability indicator from the receiver-side data transmission unit, and, if the availability indicator shows that the communication channel is available, adjusting the configuration of the remaining data of the data packet to be transmitted within the maximum permissible data transmission time which is still available for the data packet and transmitting the remaining data to the receiver-side data transmission unit. A transmitter-side data transmission unit and a receiver-side data transmission unit configured to execute the data transmission method are also provided.