An overview of OFDM and related techniques towards development of future wireless multimedia communications

In future wireless broadband communication systems, to meet demands, data rates are expected to exceed several Mbps. Consequently, the delay time of the delayed waves can typically become greater than the duration of one symbol and delay spread handling by traditional adaptive equalization is not an easy task. OFDM (orthogonal frequency division multiplexing) is a spectrum efficient kind of multicarrier transmission. Using OFDM-techniques makes it possible to reduce the effects of multipath fading and thus complex equalizers at the receiver side can be avoided. The principles, technology and limits of OFDM are introduced and discussed. Special attention is given to SNR-problems and to synchronization in time and frequency at the receiver. OFDM is a strong candidate for the future generation of wireless communications. The performance of an OFDM-based system is limited by the system speed and the synchronization-ability and also by the given antenna concept. Thus the required future communication performance is not obtained only by improvements of the OFDM-concept but also by advanced diversity techniques and adaptive antenna technology.