Blind space-time detection in asynchronous multipath CDMA channels

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