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Blind adaptive and iterative algorithms for decision feedback DS-CDMA receivers in dispersive channels

In this paper we examine blind adaptive and iterative decision feedback (DF) receivers for direct sequence code division multiple access (DS-CDMA) systems in frequency selective channels. Code-constrained minimum variance (CMV) and constant modulus (CCM) design criteria for DF receivers based on constrained optimization techniques are investigated for scenarios subject to multipath. Computationally efficient blind adaptive recursive least squares (RLS) algorithms are developed for estimating the parameters of DF detectors along with successive, parallel and iterative DF structures. A new successive parallel arbitrated DF scheme is presented and combined with iterative techniques for use with cascaded DF stages for mitigating the deleterious effects of error propagation. Simulations for an uplink scenario assess the new blind algorithms, DF structures and the effects of error propagation of the new techniques