Detection of spread-spectrum signals in a multi-user environment

Code-division multiple-access (CDMA) is emerging as a desirable protocol by which multiple users can simultaneously share a communication channel. Motivated by a previous study of adaptive multi-user demodulators for direct-sequence spread-spectrum multiple access, detectors for spread-spectrum signals are investigated. Due to the prohibitive complexity of the locally optimum detector for such a stochastic multi-variate signal in impulsive channel noise, moderate complexity distribution-free detectors are pursued. In particular, the differential SNRs (processing gain) of correlator based structures are determined. This performance measure is apt given the relatively low signal strength of spread digital signals. The numerical results (in the context of the prior investigation of adaptive multi-user demodulators) impel the development of a hybrid detector which is composed of linear and nonlinear structures. The asymptotic normality of the test statistics under study is also examined.