6,132 research outputs found
Orthogonal Designs and a Cubic Binary Function
Orthogonal designs are fundamental mathematical notions used in the
construction of space time block codes for wireless transmissions. Designs have
two important parameters, the rate and the decoding delay; the main problem of
the theory is to construct designs maximizing the rate and minimizing the
decoding delay. All known constructions of CODs are inductive or algorithmic.
In this paper, we present an explicit construction of optimal CODs. We do not
apply recurrent procedures and do calculate the matrix elements directly. Our
formula is based on a cubic function in two binary n-vectors. In our previous
work (Comm. Math. Phys., 2010, and J. Pure and Appl. Algebra, 2011), we used
this function to define a series of non-associative algebras generalizing the
classical algebra of octonions and to obtain sum of squares identities of
Hurwitz-Radon type
Structure theorem of square complex orthogonal design
Square COD (complex orthogonal design) with size is an matrix , where each entry is a complex linear combination of
and their conjugations , , such that
. Closely
following the work of Hottinen and Tirkkonen, which proved an upper bound of
by making a crucial observation between square COD and group
representation, we prove the structure theorem of square COD
Space Frequency Codes from Spherical Codes
A new design method for high rate, fully diverse ('spherical') space
frequency codes for MIMO-OFDM systems is proposed, which works for arbitrary
numbers of antennas and subcarriers. The construction exploits a differential
geometric connection between spherical codes and space time codes. The former
are well studied e.g. in the context of optimal sequence design in CDMA
systems, while the latter serve as basic building blocks for space frequency
codes. In addition a decoding algorithm with moderate complexity is presented.
This is achieved by a lattice based construction of spherical codes, which
permits lattice decoding algorithms and thus offers a substantial reduction of
complexity.Comment: 5 pages. Final version for the 2005 IEEE International Symposium on
Information Theor
Quasi-orthogonal space-frequency coding in non-coherent cooperative broadband networks
© 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.So far, complex valued orthogonal codes have been used differentially in cooperative broadband networks. These codes however achieve less than unitary code rate when utilized in cooperative networks with more than two relays. Therefore, the main challenge is how to construct unitary rate codes for non-coherent cooperative broadband networks with more than two relays while exploiting the achievable spatial and frequency diversity. In this paper, we extend full rate quasi-orthogonal codes to differential cooperative broadband networks where channel information is unavailable. From this, we propose a generalized differential distributed quasi-orthogonal space-frequency coding (DQSFC) protocol for cooperative broadband networks. Our proposed scheme is able to achieve full rate, and full spatial and frequency diversity in cooperative networks with any number of relays. Through pairwise error probability analysis we show that the diversity gain of our scheme can be improved by appropriate code construction and sub-carrier allocation. Based on this, we derive sufficient conditions for the proposed code structure at the source node and relay nodes to achieve full spatial and frequency diversity.Peer reviewe
A High-Diversity Transceiver Design for MISO Broadcast Channels
In this paper, the outage behavior and diversity order of the mixture
transceiver architecture for multiple-input single-output broadcast channels
are analyzed. The mixture scheme groups users with closely-aligned channels and
applies superposition coding and successive interference cancellation decoding
to each group composed of users with closely-aligned channels, while applying
zero-forcing beamforming across semi-orthogonal user groups. In order to enable
such analysis, closed-form lower bounds on the achievable rates of a general
multiple-input single-output broadcast channel with superposition coding and
successive interference cancellation are newly derived. By employing
channel-adaptive user grouping and proper power allocation, which ensures that
the channel subspaces of user groups have angle larger than a certain
threshold, it is shown that the mixture transceiver architecture achieves full
diversity order in multiple-input single-output broadcast channels and
opportunistically increases the multiplexing gain while achieving full
diversity order. Furthermore, the achieved full diversity order is the same as
that of the single-user maximum ratio transmit beamforming. Hence, the mixture
scheme can provide reliable communication under channel fading for
ultra-reliable low latency communication. Numerical results validate our
analysis and show the outage superiority of the mixture scheme over
conventional transceiver designs for multiple-input single-output broadcast
channels.Comment: The inner region is evaluated. The single-group SIC performance is
evaluate
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