A New Approach to Fast Decode Quasi-Orthogonal Space-Time Block Codes

Motivated by the statistical correspondence between phases of the transmitted and received vectors, we present a fast decoding method for quasi-orthogonal space-time block codes (QOSTBCs) in this paper. The proposed decoder selects proper candidates from precomputed and sorted sets by focusing on the phase of a specific entry of the combined and decoupled vector. The ML metric of the most probable candidates is first evaluated, and then, the remaining candidates are assessed based on the similarity between the phases. The new algorithm can work with any type of constellation such as QAM and PSK and supports generalized block-diagonal QOSTBCs. Theoretical results backed by simulation tests confirm the solution's superior performance in terms of the decoder complexity compared with popular approaches found in the literature. This feature is achieved through far fewer computations operations compared with many of the state-of-the-art models reported in the literature.