An apparatus and a corresponding method for mapping payload data of mapping input data streams onto a mapping output data stream having a channel bandwidth for transmission in a multi-carrier broadcast system includes first and second frame forming mechanisms. The first frame forming mechanism is adapted to form first frames having a first frame structure and the second frame forming mechanism is adapted to form second frames having a second frame structure. Preferably, in a second frame structure the data blocks of a particular mapping input data stream are spread in time and frequency over various data symbols and various data segments of the second frames to provide high robustness against disturbances. The payload portion of the second frame is preferably segmented into various data segments enabling use of a narrow-band receiver, even if both the first and second frames cover the same total channel bandwidth.