11,089 research outputs found
Algebraic Hybrid Satellite-Terrestrial Space-Time Codes for Digital Broadcasting in SFN
Lately, different methods for broadcasting future digital TV in a single
frequency network (SFN) have been under an intensive study. To improve the
transmission to also cover suburban and rural areas, a hybrid scheme may be
used. In hybrid transmission, the signal is transmitted both from a satellite
and from a terrestrial site. In 2008, Y. Nasser et al. proposed to use a double
layer 3D space-time (ST) code in the hybrid 4 x 2 MIMO transmission of digital
TV. In this paper, alternative codes with simpler structure are proposed for
the 4 x 2 hybrid system, and new codes are constructed for the 3 x 2 system.
The performance of the proposed codes is analyzed through computer simulations,
showing a significant improvement over simple repetition schemes. The proposed
codes prove in addition to be very robust in the presence of power imbalance
between the two sites.Comment: 14 pages, 2 figures, submitted to ISIT 201
Cyclic division algebras: a tool for space-time coding
Multiple antennas at both the transmitter and receiver ends of a wireless digital transmission channel may increase both data rate and reliability. Reliable high rate transmission over such channels can only be achieved through Space–Time coding. Rank and determinant code design criteria have been proposed to enhance diversity and coding gain. The special case of full-diversity criterion requires that the difference of any two distinct codewords has full rank.
Extensive work has been done on Space–Time coding, aiming at
finding fully diverse codes with high rate. Division algebras have been proposed as a new tool for constructing Space–Time codes, since they are non-commutative algebras that naturally yield linear fully diverse codes. Their algebraic properties can thus be further exploited to
improve the design of good codes.
The aim of this work is to provide a tutorial introduction to the algebraic tools involved in the design of codes based on cyclic division algebras. The different design criteria involved will be illustrated, including the constellation shaping, the information lossless property, the non-vanishing determinant property, and the diversity multiplexing trade-off. The final target is to give the complete mathematical background underlying the construction of the Golden code and the other Perfect Space–Time block codes
Studies on the Seismic Design of Low-Rise Steel Buildings
The behavior of low-rise steel shear buildings, moment frame buildings,
and X-braced buildings, subjected to earthquake base motion, is studied using inelastic
time-history analysis. Two simpler methods of analysis, the modal method
and the quasi-static building code approach, are evaluated for practical use in
calculating. response quantities. The application of the results of these studies
to the practical design of buildings is discussed.National Science Foundation Grant No. AEN 75-0845
Diversity gain for DVB-H by using transmitter/receiver cyclic delay diversity
The objective of this paper is to investigate different diversity techniques for broadcast networks that will minimize the complexity and improve received SNR of broadcast systems.
Resultant digital broadcast networks would require fewer transmitter sites and thus be more cost-effective and have less environmental impact. The techniques can be applied to DVB-T,
DVB-H and DAB systems that use Orthogonal Frequency Division Multplexing (OFDM). These are key radio broadcast network technologies, which are expected to complement emerging technologies
such as WiMAX and future 4G networks for delivery
of broadband content. Transmitter and receiver diversity technologies can increase the frequency and time selectivity of the resulting channel transfer function at the receiver. Diversity exploits the statistical nature of fading due to multipath and reduces the likelihood of deep fading by providing a diversity of transmission signals. Multiple signals are transmitted in such
a way as to ensure that several signals reach the receiver each with uncorrelated fading. Transmit diversity is more practical than receive diversity due to the difficulty of locating two receive antennas far enough apart in a small mobile device. The schemes examined here comply with existing DVB standards and can be incorporated into existing systems without change. The diversity techniques introduced in this paper are applied to the DVB-H system. Bit error performance investigations were conducted by
simulation for different DVB-H and diversity parameters
Analysis and Design of Tuned Turbo Codes
It has been widely observed that there exists a fundamental trade-off between
the minimum (Hamming) distance properties and the iterative decoding
convergence behavior of turbo-like codes. While capacity achieving code
ensembles typically are asymptotically bad in the sense that their minimum
distance does not grow linearly with block length, and they therefore exhibit
an error floor at moderate-to-high signal to noise ratios, asymptotically good
codes usually converge further away from channel capacity. In this paper, we
introduce the concept of tuned turbo codes, a family of asymptotically good
hybrid concatenated code ensembles, where asymptotic minimum distance growth
rates, convergence thresholds, and code rates can be traded-off using two
tuning parameters, {\lambda} and {\mu}. By decreasing {\lambda}, the asymptotic
minimum distance growth rate is reduced in exchange for improved iterative
decoding convergence behavior, while increasing {\lambda} raises the asymptotic
minimum distance growth rate at the expense of worse convergence behavior, and
thus the code performance can be tuned to fit the desired application. By
decreasing {\mu}, a similar tuning behavior can be achieved for higher rate
code ensembles.Comment: Accepted for publication in IEEE Transactions on Information Theor
- …