A blind adaptive interference cancellation scheme for CDMA systems

Abstract

An interference cancellation scheme for CDMA communication systems is presented. The algorithm is based on constrained optimization where receiver output power is minimized subject to the constraint that a desired code be passed with no distortion. Output power minimization (OPM) schemes have been shown to be equivalent to minimum mean square error (MMSE) approaches. Like MMSE approaches, OPM schemes do not require explicit knowledge of the interference structure. Unlike most MMSE approaches, however, OPM schemes do not require training. The algorithms are blind in the sense that only knowledge of the desired user's code (not the actual transmitted bit sequence) and associated timing is necessary. Moreover, the algorithms are linear and, therefore, not susceptible to misconvergence. The particular OPM implementation presented is based on the generalized sidelobe canceller structure which was originally developed for adaptive cancellation of spatial interference in array signal processing applications. Algorithm performance results are presented in the form of signal to interference ratios and bit error rate curves.