DETECTION METHOD FOR THE TRANSMITTER IDENTIFICATION INFORMATION SIGNAL IN THE NULL SYMBOL OF A DAB STREAM

摘要

A DAB stream starts with a so-called null symbol for the receiver synchroniz a- tion 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 patter n 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 an d 2 times, respectively. For mode III only a half block is available. This patte rn is transmitted every 2nd DAB frame in the null symbol. To detect the set carriers the steps of differential demodulation of TII pai rs in-cluded in the spectrum (S1(.omega.)) of every second null symbol of the incoming DAB stream (S1, S2, S3) to respectively obtain a demodulated null symbol, correction of carrier phases of the demodulated null symbol spectrum (S4), de-termination of a threshold. (S7), and decision if a carrier is set or not by com-paring the carrier level to the determined threshold (56) are performe d.