Abstract: The establishment of an interactive broadcasting network requires not only a transmission channel from transmitter to receiver but also a transmission channel from receiver to transmitter. A novel method of creating a data feedback channel from receiver to transmitter is implemented in a common frequency network and involves the use of a transmission procedure in conformity with the DAB standard. Each receiver or user is assigned an identifier which is transmitted in the data feedback channel at specially reserved frequencies to request transmission capacity. A computer then allocates transmission capacity to the receiver. The signals received in the forward channel are evaluated using the synchronization symbols they contain in order to synchronize the transmitter component in the receiver. The novel process can be used in all common frequency networks which use data transmission in conformity with the DAB standard and ensures a particularly economical synchronization in the receiver.

Abstract: A DAB stream starts with a so-called null symbol for the receiver synchronization carrying a transmitter identification information, i.e. TII, signal. Each transmitter in the single frequency network is assigned a main id and a sub id for unique identification. This identification is mapped to a certain pattern with 16/8/4/2 set carrier pairs in the spectrum of the null symbol according to the DAB modes I-IV. Based on mode II which has 384 valid carriers a so called comb block is defined. For modes I and IV this block is repeated 4 and 2 times, respectively. For mode III only a half block is available. This pattern is transmitted every 2nd DAB frame in the null symbol.To detect the set carriers the steps of differential demodulation of TII pairs included in the spectrum (S.sub.1 (.omega.

Abstract: The common-wave broadcasting of radio programs is known in the art. Common-wave operation of radio transmitters allows the available transmission band width to be particularly well utilized, for example for national scale common-wave broadcasts. A new process now allows a stereo transmission channel to be divided into two mono transmission channels during radio broadcasts and to broadcast certain programs only through particular transmitters. Information concerning the division of the stereo transmission channel into two mono transmission channels is further broadcast over the entire common-wave transmission network. This information causes receivers tuned to this transmission channel to automatically switch to mono evaluation of the reception signal. On a regional level, information may also be broadcast concerning which of both mono transmission channels may be received. Alternatively, the receiver or user himself may select the mono transmission channel he wishes to receive.