Transmit Power Allocation among Orthogonal Pulse Wavelets for BER Performance Improvement in Cognitive UWB Radio

Abstract

Ultra Wideband (UWB) technology has been considered as one of the suitable transmission techniques for implementing a cognitive radio system, where spectrum-agile UWB waveforms achieve a number of spectral adaptation features. One approach for designing such waveforms relies on orthogonally combining PSWF (Prolate Spheroidal Wave Functions) based pulse wavelets. In a cognitive UWB radio environment when the transmit signal is M-ary pulse shape modulated, we can obtain M different eigenvalues corresponding to the M PSWF-based pulses while transmitting them through the multipath fading channel. Each eigenvalue represents the multipath channel gain for its corresponding pulse. We propose an optimal power allocation scheme depending on the eigenvalues to improve bit error rate (BER) performance in such a cognitive UWB radio environment. Numerical results show that the scheme outperforms the general equal power allocation scheme.