Blind and semiblind optimum demodulation in multiuser communications

This paper addresses the problem of blind and semiblind channel estimation and detection in multiuser communications. The proposed receivers are optimum in the sense that they make full use of the available statistical information to compute the maximum likelihood (ML) estimate of the multiuser channel using the expectation maximization (EM) algorithm and perform ML detection of the transmitted symbols. Computer simulations show that both proposed demodulators attain optimum performance in code division multiple access (CDMA) time dispersive channels. The semiblind approach, in addition, is highly robust to the local misconvergence problems of the EM algorithm