Evaluation of protection ratios on COFDM for in-band adjacent-channel digital audio broadcasting

The IBAC (in-band adjacent-channel) DAB (digital audio broadcasting) system proposed is able to provide simultaneously multichannel CD quality audio services and multimedia data services including text and pictures in the FM band. As the FM band is being used by the existing analog radio broadcasting, interference between IBAC DAB and analog FM signals may occur. Therefore, the protection ratios should be evaluated to verify the system compatibility and to allocate the new IBAC DAB channel in the FM band. This paper presents the derivation of protection ratios of the IBAC DAB system for FM and IBAC DAB interferer under EIA Rayleigh multipath channel. The simulation results show that the protection ratios of the IBAC DAB system with time interleaving depth of 256ms for co-channel FM and DAB interference are 16.3 to 18.6dB and 18.5 to 20.3dB respectively in four different multipath channels