Orthogonal Basis Functions and Equalizer Design for Multicarrier Transmission Systems

摘要

Multicarrier transmission systems represent a possible transmission concept for future mobile communication systems. In today's typical multicarrier system OFDM (orthogonal frequency division multiplex) a guard interval is used to maintain the orthogonality. The cancellation of this guard-interval allows higher information rates. However, intersymbol and interchannel disturbances (ISI and ICI) arise in the case, when a non-ideal channel is introduced. In this contribution different receiver concepts are analyzed, which enable a reliable data transmission in spite of disturbances (non-orthogonality, intersymbol interference, noise disturbances). We investigate different equalizer strategies (e.g. data-directed equalization) in combination with different pulse shaping concepts (e. g. filtered multitone modulation and wavelet-packet modulation) under non-ideal channel conditions. As a result of the investigations it is shown, that the equalizer has to take both disturbances (ISI and ICI) in a multicarrier system into account in order to obtain good results. The application of well-known equalizer strategies from the single-carrier transmission (per subchannel) leads only to poor results, since only one disturbance variable is considered in the equalizer design.