On Decoupling of Quasi-Orthogonal Space-Time Block Codes based on Inherent Structure

In this paper we propose a linear decoupling scheme for multiple-input multiple-output (MIMO) antenna systems where spatial diversity is exploited through complex orthogonal (COD) or quasi-orthogonal (CQOD) designs. The proposed scheme is based on rewriting the space-time block code (STBC) in an alternative form via generalized permutation matrices (GPM) and transforming the original system to an equivalent one, where all the transmitted symbols are decoupled, allowing thus a single symbol or symbol pair-wise maximum likelihood decoding (MLD) through a closed form expression (CFE).