22 Signaling Overhead in Time-Invariant OFDM Systems with Adaptive Techniques

To realize “global information village (GIV)” the followed conditions must be fulfilled, high data rate wireless communication; high robustness; low cost. Orthogonal Frequency Division Multiplexing (OFDM) technique seems to be one of the best candidates to fulfill the above requirements. As a matter of fact, OFDM is the one candidate of 4G mobile communications. In this work one aspect of OFDM technique will be treated namely adaptive modulation techniques, where information is adaptively modulated on each subcarrier based on the current channel state. Emphasis will be put on the signaling overhead, which is necessary to inform the receiver which modulation method is applied on which subcarriers.