46 research outputs found
Optimization of Fast-Decodable Full-Rate STBC with Non-Vanishing Determinants
Full-rate STBC (space-time block codes) with non-vanishing determinants
achieve the optimal diversity-multiplexing tradeoff but incur high decoding
complexity. To permit fast decoding, Sezginer, Sari and Biglieri proposed an
STBC structure with special QR decomposition characteristics. In this paper, we
adopt a simplified form of this fast-decodable code structure and present a new
way to optimize the code analytically. We show that the signal constellation
topology (such as QAM, APSK, or PSK) has a critical impact on the existence of
non-vanishing determinants of the full-rate STBC. In particular, we show for
the first time that, in order for APSK-STBC to achieve non-vanishing
determinant, an APSK constellation topology with constellation points lying on
square grid and ring radius \sqrt{m^2+n^2} (m,n\emph{\emph{integers}}) needs
to be used. For signal constellations with vanishing determinants, we present a
methodology to analytically optimize the full-rate STBC at specific
constellation dimension.Comment: Accepted by IEEE Transactions on Communication
Asymptotically-Optimal, Fast-Decodable, Full-Diversity STBCs
For a family/sequence of STBCs , with
increasing number of transmit antennas , with rates complex symbols
per channel use (cspcu), the asymptotic normalized rate is defined as . A family of STBCs is said to be
asymptotically-good if the asymptotic normalized rate is non-zero, i.e., when
the rate scales as a non-zero fraction of the number of transmit antennas, and
the family of STBCs is said to be asymptotically-optimal if the asymptotic
normalized rate is 1, which is the maximum possible value. In this paper, we
construct a new class of full-diversity STBCs that have the least ML decoding
complexity among all known codes for any number of transmit antennas and
rates cspcu. For a large set of pairs, the new codes
have lower ML decoding complexity than the codes already available in the
literature. Among the new codes, the class of full-rate codes () are
asymptotically-optimal and fast-decodable, and for have lower ML decoding
complexity than all other families of asymptotically-optimal, fast-decodable,
full-diversity STBCs available in the literature. The construction of the new
STBCs is facilitated by the following further contributions of this paper:(i)
For , we construct -group ML-decodable codes with rates greater than
one cspcu. These codes are asymptotically-good too. For , these are the
first instances of -group ML-decodable codes with rates greater than
cspcu presented in the literature. (ii) We construct a new class of
fast-group-decodable codes for all even number of transmit antennas and rates
.(iii) Given a design with full-rank linear dispersion
matrices, we show that a full-diversity STBC can be constructed from this
design by encoding the real symbols independently using only regular PAM
constellations.Comment: 16 pages, 3 tables. The title has been changed.The class of
asymptotically-good multigroup ML decodable codes has been extended to a
broader class of number of antennas. New fast-group-decodable codes and
asymptotically-optimal, fast-decodable codes have been include