Using Walsh code selection to reduce the power variance of band-limited forward-link CDMA waveforms

摘要

This paper investigates the effects of Walsh code selection and baseband filtering on the statistical moments of the band-limited forward-link CDMA signal. A normalized moment, the "power variance," is proposed as a measure of the signal's sensitivity to nonlinear amplification. The estimation of the power variance for the case of a band-limited QPSK-modulated random waveform is presented as a baseline fur illustrating the effect of filtering on a sampled signal. The band-limited CDMA signal case illustrates the interaction between the Walsh codes and the wave-shaping filter, and quantifies the influence of "missing Hadamard basis functions. "Results verify the accuracy of the statistical models and illustrate the importance of Walsh code selection in the reduction of the power variance of a band-limited CDMA waveform.