Further results on blind asynchronous CDMA receivers using code-constrained inverse filter criterion

A code-constrained inverse filter criterion (CC-IFC) based approach was presented Tugnait and Li (see Proc. IEEE 2000 ICASSP, p.V-246-64, Istanbul, Turkey, June 2000) for blind-detection of asynchronous short-code DS-CDMA (direct sequence code division multiple access) signals in multipath channels. Only the spreading code of the desired user is assumed to be known; its transmission delay may be unknown. The equalizer was determined by maximizing the magnitude of the normalized fourth cumulant of inverse filtered (equalized) data with respect to the equalizer coefficients subject to the fact that the equalizer lies in a subspace associated with the desired user's code sequence. In this paper we analyze the identifiability properties of the approach of Tugnait and Li. Global maxima and some of the local maxima of the cost function are investigated. These aspects were not discussed by Tugnait and Li. More extensive simulation comparisons with existing approaches are also provided