975 research outputs found
Square Complex Orthogonal Designs with Low PAPR and Signaling Complexity
Space-Time Block Codes from square complex orthogonal designs (SCOD) have
been extensively studied and most of the existing SCODs contain large number of
zero. The zeros in the designs result in high peak-to-average power ratio
(PAPR) and also impose a severe constraint on hardware implementation of the
code when turning off some of the transmitting antennas whenever a zero is
transmitted. Recently, rate 1/2 SCODs with no zero entry have been reported for
8 transmit antennas. In this paper, SCODs with no zero entry for transmit
antennas whenever is a power of 2, are constructed which includes the 8
transmit antennas case as a special case. More generally, for arbitrary values
of , explicit construction of rate SCODs
with the ratio of number of zero entries to the total number of entries equal
to is reported,
whereas for standard known constructions, the ratio is . The
codes presented do not result in increased signaling complexity. Simulation
results show that the codes constructed in this paper outperform the codes
using the standard construction under peak power constraint while performing
the same under average power constraint.Comment: Accepted for publication in IEEE Transactions on Wireless
Communication. 10 pages, 6 figure
A New Low-Complexity Decodable Rate-1 Full-Diversity 4 x 4 STBC with Nonvanishing Determinants
Space-time coding techniques have become common-place in wireless
communication standards as they provide an effective way to mitigate the fading
phenomena inherent in wireless channels. However, the use of Space-Time Block
Codes (STBCs) increases significantly the optimal detection complexity at the
receiver unless the low complexity decodability property is taken into
consideration in the STBC design. In this letter we propose a new
low-complexity decodable rate-1 full-diversity 4 x 4 STBC. We provide an
analytical proof that the proposed code has the Non-Vanishing-Determinant (NVD)
property, a property that can be exploited through the use of adaptive
modulation which changes the transmission rate according to the wireless
channel quality. We compare the proposed code to existing low-complexity
decodable rate-1 full-diversity 4 x 4 STBCs in terms of performance over
quasi-static Rayleigh fading channels, detection complexity and Peak-to-Average
Power Ratio (PAPR). Our code is found to provide the best performance and the
smallest PAPR which is that of the used QAM constellation at the expense of a
slight increase in detection complexity w.r.t. certain previous codes but this
will only penalize the proposed code for high-order QAM constellations.Comment: 5 pages, 3 figures, and 1 table; IEEE Transactions on Wireless
Communications, Vol. 10, No. 8, AUGUST 201
A New Low-Complexity Decodable Rate-5/4 STBC for Four Transmit Antennas with Nonvanishing Determinants
The use of Space-Time Block Codes (STBCs) increases significantly the optimal
detection complexity at the receiver unless the low-complexity decodability
property is taken into consideration in the STBC design. In this paper we
propose a new low-complexity decodable rate-5/4 full-diversity 4 x 4 STBC. We
provide an analytical proof that the proposed code has the
Non-Vanishing-Determinant (NVD) property, a property that can be exploited
through the use of adaptive modulation which changes the transmission rate
according to the wireless channel quality. We compare the proposed code to the
best existing low-complexity decodable rate-5/4 full-diversity 4 x 4 STBC in
terms of performance over quasi-static Rayleigh fading channels, worst- case
complexity, average complexity, and Peak-to-Average Power Ratio (PAPR). Our
code is found to provide better performance, lower average decoding complexity,
and lower PAPR at the expense of a slight increase in worst-case decoding
complexity.Comment: 5 pages, 2 figures and 1 table; IEEE Global Telecommunications
Conference (GLOBECOM 2011), 201
Algebraic Distributed Space-Time Codes with Low ML Decoding Complexity
"Extended Clifford algebras" are introduced as a means to obtain low ML
decoding complexity space-time block codes. Using left regular matrix
representations of two specific classes of extended Clifford algebras, two
systematic algebraic constructions of full diversity Distributed Space-Time
Codes (DSTCs) are provided for any power of two number of relays. The left
regular matrix representation has been shown to naturally result in space-time
codes meeting the additional constraints required for DSTCs. The DSTCs so
constructed have the salient feature of reduced Maximum Likelihood (ML)
decoding complexity. In particular, the ML decoding of these codes can be
performed by applying the lattice decoder algorithm on a lattice of four times
lesser dimension than what is required in general. Moreover these codes have a
uniform distribution of power among the relays and in time, thus leading to a
low Peak to Average Power Ratio at the relays.Comment: 5 pages, no figures. To appear in Proceedings of IEEE ISIT 2007,
Nice, Franc
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