The invention relates to a data transmission method and a radio system implementing method. A transmitter has at least two modulation methods by which it can modulate a signal. One or more demodulators (106) of the receiver demodulates the received signal in a manner which corresponds to each modulation method used. The modulation method used for the signal is inferred in a reference block (110) from the impulse response estimate. The signal according to the inferred modulation method is detected in a detector (114).