Constellation space invariance of orthogonal space-time block codes

• Published in: IEEE transactions on information theory Vol. 51; no. 1; pp. 331 - 334
• Main Authors: Gharavi-Alkhansari, M., Gershman, A.B.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.01.2005; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Additive white noise; Applied sciences; Block codes; Blocking; Channels; Codes; Coding, codes; Communication systems; Constellation diagram; Constellation space invariance; Constellations; Decoders; Decoding; Educational programs; Exact sciences and technology; Fading; Information systems; Information, signal and communications theory; Invariants; Maximum likelihood decoding; maximum-likelihood (ML) decoding; Mechanical factors; MIMO; Optimization; orthogonal space-time block codes (OSTBCs); Signal and communications theory; Telecommunications and information theory; Transmitters; Wireless networks; Fading channels; MIMO system; Block code; orthogonal space-time block codes (OSTBCs); Space time; Constellation space invariance; maximum-likelihood (ML) decoding; Maximum likelihood decoding
• ISSN: 0018-9448; 1557-9654
• DOI: 10.1109/TIT.2004.839533

In this correspondence, we prove an interesting property of orthogonal space-time block codes (OSTBCs). For flat block-fading channels, it is shown that the internal structure of the vector space of the input constellation remains invariant to the effects of both the OSTBC and the channel except for certain scaling factors. This property sheds light on the mechanism of maximum-likelihood (ML) decoding of OSTBCs and, in particular, provides an alternative explanation of why optimal decoding can be reduced to symbol-by-symbol decoding. New simple expressions for the ML decoder are obtained which clarify its intrinsic structure.