Blind space-time detection in asynchronous multipath CDMA channels
JITENDRA K. TUGNAIT · 2002
A code-constrained inverse filter criterion based approach is presented for blind detection of asynchronous short-code DS-CDMA (direct sequence code division multiple access) signals in multipath channels using a receiver antenna array. Only the spreading code of the desired user is assumed to be known; its transmission delay may be unknown. We exploit maximization of the normalized fourth cumulant of inverse filtered (equalized) data w.r.t. the equalizer coefficients subject to the equalizer lying in a subspace associated with the desired user's code sequence. Constrained maximization leads to extraction of the desired user's signal whereas unconstrained maximization leads to the extraction of any one of the existing users. An illustrative simulation example is provided.