On the reduction of the out-of-band radiation of OFDM-signals

OFDM is very suitable as a modulation scheme for future indoor mobile radio systems due to its simple realization and the resistance to interference caused by frequency-selective fading. Opposed to the various advantages of OFDM there is the disadvantage of a nonconstant envelope that, in the case of a nonlinear characteristic of the transmitter amplifier, leads to undesirable out-of-band radiation. Results concerning the reduction of out-of-band radiation are presented which were achieved by a new method we call BERC (bandwidth efficient reduction of the crest factor). Furthermore, the performance of an algorithm to decrease the out-of-band radiation caused by the rectangular shape of the basic pulse is investigated.