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Using Walsh Code Selection to Reduce the Power Variance of Bandlimited Forward-link CDMA Waveforms
Braithwaite, R. Neil
HPL-1999-87
Keyword(s): wireless communications; CDMA; multiaccess communication; intermodulation distortion
Abstract: This paper investigates the effects of Walsh code selection and baseband filtering on the statistical moments of the bandlimited 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 bandlimited QPSK-modulated random waveform is presented as a baseline for illustrating the effect of filtering on a sampled signal. The bandlimited 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 bandlimited CDMA waveform.
25 Pages
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