PERFORMANCE EVALUATION OF COFDM FOR DIGITAL AUDIO BROADCASTING .1. PARAMETRIC STUDY

This paper describes the performance of COFDM for digital audio broadc asting (DAB) over various multipath mobile radio channels. COFDM is a channel coding and modulation scheme which mitigates the adverse effec ts of fading by using wideband multicarrier modulation combined with t ime interleaving and a convolutional error correcting code. A guard in terval is inserted at the transition between successive symbols to abs orb the intersymbol interference created by the time domain spread of the mobile radio channel. The decoding process is performed using diff erential demodulation in conjunction with a soft decision Viterbi deco der. The COFDM evaluation is done by means of computer simulations. A parametric study of the proposed COFDM system is done in this first of a series of papers to determine the optimal system parameter values f or operation at a radio frequency of 1.5 GHz. The results show that th e parameter values proposed in the standard are indeed well suited for operation at 1.5 GHz. Using the set of optimal parameter values found , the COFDM performance is then evaluated in mobile radio channels typ ical of different geographical environments. Simulation results confir m the benefit that the system gains from frequency diversity found in the urban and hilly terrain areas.