CDMA over QAM and other Arbitrary Energy Constellations

Abstract

Welch and Sidelnikov lower bounds on the maximum nontrivial correlations of complex signal sets apply to the constrained case of uniform signal energy and have long been used as a benchmark for testing the merit of signal sets in the design of good CDMA sequence families. Welch's lower bound is generalized here to the arbitrary signal energy case and applied to CDMA over QAM modulation. The generalized lower bound is compared to the original bound and an explicit QAM-CDMA family is constructed.