Application of blind second order statistics MIMO identification methods to the blind CDMA forward link channel estimation

Blind channel estimation for periodic sequence DS-CDMA systems can be cast into the framework of "structured" blind estimation of multi-input/multi-output (MIMO) FIR systems, where the structure is imposed by the user's signatures. A possible approach to tackle this problem consists in looking for a structured solution to one of the so-called "blind" MIMO-FIR system identification techniques proposed previously. This is the approach undertaken, among others, by Wang and Poor (see IEEE Trans. on Communications, vol.46, no.1, p.92-103, 1998), who proposed an adaptation of the subspace method originally developed by Moulines et al. (see IEEE Trans. on Signal Processing, vol.43, no.2, p.516-25, 1995) for single-input multiple outputs (SIMO) FIR systems, and later extended by Abed-Meraim et al. (see IEEE Trans. on Information Theory, vol.43, no.2, p.499-511, 1997) to MIMO-FIR systems. In this article, we follow this approach to consider the particular blind forward channel estimation problem, and improve quite significantly the results presented by Wang and Poor.