Closed-form blind and semi-blind estimation of linear receivers for space-time coding

This paper exploits a special class of space-time codes in which linearly transformed versions of a given data sequence are transmitted from multiple antennas. Several recently proposed codes, including space-time block codes, are members of this class. The redundancy introduced by the transformations imposes structure on the received data that under certain conditions can be exploited for direct blind (and semi-blind) estimation of a linear zero-forcing receiver that recovers the original data sequence. If the transmitted symbols are constant modulus, the space-time code structure can be exploited by the analytic constant modulus (ACM) algorithm to simplify the separation of multiple co-channel users. If each user employs a different code or only one user is present, the ACM joint diagonalization step can be eliminated even though multiple constant modulus data streams are received