Blind symbol identifiability of orthogonal space-time block codes

ABSTRACT This paper addresses the blind symbol identifiability of the orthogonal space-time block code (OSTBC) scheme. That is, the conditions under which OSTBC symbols can be identified without ambiguity when channel state information is not available. In many space-time communication schemes, achieving unique blind symbol identification requires certain assumptions on the number of receiver antennas and the rank of the channel matrix. In this paper we show that unique blind symbol identification of OSTBCs is possible for any number of receiver antennas and for any (nonzero) channel matrix. This attractive unique identifiability result is shown to be achieved by a class of OSTBCs that exhibit certain matrix non-rotational properties. Using these properties, we validate the identifiability of a number of commonly used OSTBCs

Efficient Blind Receiver Design for Orthogonal Space-Time Block Codes

We consider stochastic blind maximum-likelihood detection of orthogonal space-time block codes (OSTBCs) over a quasi-static flat multiple-input multiple-output (MIMO) Rayleigh fading channel. A general decision rule for stochastic blind maximum-likelihood OSTBC detection is derived. This rule is simplified using OSTBC linear dispersion matrices to realize a blind detector, which is implemented by semi-definite relaxation or sphere decoding. For the latter, the modifications necessary for both unitary and non-unitary constellations are developed. Two totally blind detectors using dual constellations or a superimposed training scheme are proposed. As a side product, two conditions for a rotatable OSTBC are also derived. A decision-directed, minimum mean-square-error (MMSE) channel estimator is developed. We also derive the Cramer-Rao bound (CRB) for channel estimation and discuss the optimal power allocation. Extensive simulation results are used to compare the different detectors in terms of complexity and performance