11,188 research outputs found
Low-delay, High-rate Non-square Complex Orthogonal Designs
The maximal rate of a non-square complex orthogonal design for transmit
antennas is if is even and if is
odd and the codes have been constructed for all by Liang (IEEE Trans.
Inform. Theory, 2003) and Lu et al. (IEEE Trans. Inform. Theory, 2005) to
achieve this rate. A lower bound on the decoding delay of maximal-rate complex
orthogonal designs has been obtained by Adams et al. (IEEE Trans. Inform.
Theory, 2007) and it is observed that Liang's construction achieves the bound
on delay for equal to 1 and 3 modulo 4 while Lu et al.'s construction
achieves the bound for mod 4. For mod 4, Adams et al. (IEEE
Trans. Inform. Theory, 2010) have shown that the minimal decoding delay is
twice the lower bound, in which case, both Liang's and Lu at al.'s construction
achieve the minimum decoding delay. % when mod 4. For large value of ,
it is observed that the rate is close to half and the decoding delay is very
large. A class of rate-1/2 codes with low decoding delay for all has been
constructed by Tarokh et al. (IEEE Trans. Inform. Theory, 1999). % have
constructed a class of rate-1/2 codes with low decoding delay for all . In
this paper, another class of rate-1/2 codes is constructed for all in which
case the decoding delay is half the decoding delay of the rate-1/2 codes given
by Tarokh et al. This is achieved by giving first a general construction of
square real orthogonal designs which includes as special cases the well-known
constructions of Adams, Lax and Phillips and the construction of Geramita and
Pullman, and then making use of it to obtain the desired rate-1/2 codes. For
the case of 9 transmit antennas, the proposed rate-1/2 code is shown to be of
minimal-delay.Comment: To appear in IEEE Transactions on Information Theor
High Rate Single-Symbol Decodable Precoded DSTBCs for Cooperative Networks
Distributed Orthogonal Space-Time Block Codes (DOSTBCs) achieving full
diversity order and single-symbol ML decodability have been introduced recently
for cooperative networks and an upper-bound on the maximal rate of such codes
along with code constructions has been presented. In this report, we introduce
a new class of Distributed STBCs called Semi-orthogonal Precoded Distributed
Single-Symbol Decodable STBCs (S-PDSSDC) wherein, the source performs
co-ordinate interleaving of information symbols appropriately before
transmitting it to all the relays. It is shown that DOSTBCs are a special case
of S-PDSSDCs. A special class of S-PDSSDCs having diagonal covariance matrix at
the destination is studied and an upper bound on the maximal rate of such codes
is derived. The bounds obtained are approximately twice larger than that of the
DOSTBCs. A systematic construction of S-PDSSDCs is presented when the number of
relays . The constructed codes are shown to achieve the upper-bound
on the rate when is of the form 0 modulo 4 or 3 modulo 4. For the rest of
the values of , the constructed codes are shown to have rates higher than
that of DOSTBCs. It is also shown that S-PDSSDCs cannot be constructed with any
form of linear processing at the relays when the source doesn't perform
co-ordinate interleaving of the information symbols.Comment: A technical report of DRDO-IISc Programme on Advanced Research in
Mathematical Engineerin
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
Four-Group Decodable Space-Time Block Codes
Two new rate-one full-diversity space-time block codes (STBC) are proposed.
They are characterized by the \emph{lowest decoding complexity} among the known
rate-one STBC, arising due to the complete separability of the transmitted
symbols into four groups for maximum likelihood detection. The first and the
second codes are delay-optimal if the number of transmit antennas is a power of
2 and even, respectively. The exact pair-wise error probability is derived to
allow for the performance optimization of the two codes. Compared with existing
low-decoding complexity STBC, the two new codes offer several advantages such
as higher code rate, lower encoding/decoding delay and complexity, lower
peak-to-average power ratio, and better performance.Comment: 1 figure. Accepted for publication in IEEE Trans. on Signal
Processin
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