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.