2 research outputs found
Generalized Silver Codes
For an transmit, receive antenna system (
system), a {\it{full-rate}} space time block code (STBC) transmits complex symbols per channel use. The well known Golden code is an
example of a full-rate, full-diversity STBC for 2 transmit antennas. Its
ML-decoding complexity is of the order of for square -QAM. The
Silver code for 2 transmit antennas has all the desirable properties of the
Golden code except its coding gain, but offers lower ML-decoding complexity of
the order of . Importantly, the slight loss in coding gain is negligible
compared to the advantage it offers in terms of lowering the ML-decoding
complexity. For higher number of transmit antennas, the best known codes are
the Perfect codes, which are full-rate, full-diversity, information lossless
codes (for ) but have a high ML-decoding complexity of the order
of (for , the punctured Perfect codes are
considered). In this paper, a scheme to obtain full-rate STBCs for
transmit antennas and any with reduced ML-decoding complexity of the
order of , is presented. The codes constructed are
also information lossless for , like the Perfect codes and allow
higher mutual information than the comparable punctured Perfect codes for . These codes are referred to as the {\it generalized Silver codes},
since they enjoy the same desirable properties as the comparable Perfect codes
(except possibly the coding gain) with lower ML-decoding complexity, analogous
to the Silver-Golden codes for 2 transmit antennas. Simulation results of the
symbol error rates for 4 and 8 transmit antennas show that the generalized
Silver codes match the punctured Perfect codes in error performance while
offering lower ML-decoding complexity.Comment: Accepted for publication in the IEEE Transactions on Information
Theory. This revised version has 30 pages, 7 figures and Section III has been
completely revise
Block-Orthogonal Space-Time Code Structure and Its Impact on QRDM Decoding Complexity Reduction
Full-rate space time codes (STC) with rate = number of transmit antennas have
high multiplexing gain, but high decoding complexity even when decoded using
reduced-complexity decoders such as sphere or QRDM decoders. In this paper, we
introduce a new code property of STC called block-orthogonal property, which
can be exploited by QR-decomposition-based decoders to achieve significant
decoding complexity reduction without performance loss. We show that such
complexity reduction principle can benefit the existing algebraic codes such as
Perfect and DjABBA codes due to their inherent (but previously undiscovered)
block-orthogonal property. In addition, we construct and optimize new full-rate
BOSTC (Block-Orthogonal STC) that further maximize the QRDM complexity
reduction potential. Simulation results of bit error rate (BER) performance
against decoding complexity show that the new BOSTC outperforms all previously
known codes as long as the QRDM decoder operates in reduced-complexity mode,
and the code exhibits a desirable complexity saturation property.Comment: IEEE Journal of Selected Topics in Signal Processing, Vol. 5, No. 8,
December 201