Broad-band OFDM radio transmission for multimedia applications

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Abstract
Future multimedia services will require the transmission of very high data rates over broad-band radio channels. In order to provide these services to mobile users, an appropriate transmission technique has to cope with frequency-selective and time-variant radio channels. The computation complexity for an equalizer in- creases in a frequency-selective radio channel for high data-rate applications. Furthermore, the overhead for channel estimation procedures increases in time-variant channels. To overcome these drawbacks orthogonal frequency division multiplexing (OFDM) has been considered for broad-band appli- cations in many publications. The objective of this paper is to describe the large potential, the flexibility and adaptivity of the OFDM transmission technique in frequency-selective and time- variant radio channels. In this paper several technical aspects of OFDM transmission systems are discussed, especially the topics of differential modulation for which we compare different demod- ulation methods and channel coding with soft decision decoding. For higher level differential modulation, multilevel coding is taken into consideration.