EM-based blind demodulation of synchronous CDMA

The problem of blind detection in a synchronous CDMA system when there is no knowledge of the users' spreading sequences is considered. An EM-based algorithm which exploits the finite alphabet property of the digital communications source is proposed. Simulations show that this approach, which makes use of knowledge of the subspace spanned by the signaling multiplex, achieves the Cramer-Rao lower bound. The issues of subspace estimation and timing acquisition are also considered.