A data transmission system includes a transmitter configured to transmit a data signal in the form of a data stream of data bursts in at least two transmission modes to a receiver, in the first mode a reference signal being transmitted by the transmitter in each data burst and being evaluated in the receiver, and in the second mode no reference signal being transmitted by the transmitter in each data burst. In the second mode, in place of the reference signal, additional redundancy data of the data signal are transmitted in each data burst.