Optimal Power Allocation in SVD Equalized Multicarrier Systems

Multicarrier transmission is an established technique for radio transmission systems and it can be considered as a promising approach for next generation wireless systems. In channel situations with high delay-spreads, OFDM requires large guard interval lengths which decrease the spectral efficiency significantly. Therefore, alternative multicarrier transmission systems are of great practical interest, which guarantee a reliable transmission without a guard interval. In multicarrier systems the subcarriers are weighted in a quite different way by the frequency selective channel, based on the inherent structure of the multicarrier transmission system. If the transmitter knows the channel, the subchannel´s transmission parameters such as transmit power or modulation alphabets can be adapted. In this contribution, transmit power allocation schemes for BER performance improvements in a wavelet-based multicarrier transmission system with SVD equalization (singular value decomposition) are investigated under the constraints of a limited total transmit power and a given data rate. Thereby the differences between the optimal but highly complex solution and suboptimal but complexity-reduced solutions are analyzed. Numerical results are obtained by simulations assuming different time-variant channel characteristics, with delays larger than the multicarrier symbol duration.