Blind adaptive multiuser CDMA detection based on a linear projection constraint

Minimum output energy (MOE) detection has recently been proposed for code-division multiple-access (CDMA) systems. The MOE detector can be blindly adapted with standard adaptive algorithms without the knowledge of interferer´s parameters. But the performance of the MOE detector may degrade substantially if the multipath interference causes a signature mismatch. A projection-based blind adaptive multiuser detector is proposed. The proposed detector is motivated by the linearity of multipath interference. We construct a subspace that is orthogonal to the space spanned by the desired signature vector with different possible delays. If the steering vector is in the orthogonal subspace in each step of the adaptive algorithm, there is no cancellation of the desired signal. Thus better performance can be expected in the presence of linear multipath interferences.