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ABSTRACT: An efficient soft-input soft-output iterative decoding algorithm
for block turbo codes (BTCs) is proposed. The proposed algorithm
utilizes Kaneko's (1994) decoding algorithm for soft-input hard-output
decoding. These hard outputs are converted to soft-decisions using
reliability calculations. Three different schemes for reliability
calculations incorporating different levels of approximation are
suggested. The algorithm proposed here presents a major advantage over
existing decoding algorithms for BTCs by providing ample flexibility in
terms of performance-complexity tradeoff. This makes the algorithm well
suited for wireless multimedia applications. The algorithm can be used
for optimal as well as suboptimal decoding. The suboptimal versions of
the algorithm can be developed by changing a single parameter (the
number of error patterns to be generated). For any performance, the
computational complexity of the proposed algorithm is less than the
computational complexity of similar existing algorithms. Simulation
results for the decoding algorithm for different two-dimensional BTCs
over an additive white Gaussian noise channel are shown. A performance
comparison of the proposed algorithm with similar existing algorithms is
also presented
IEEE Transactions on Communications 02/2001; · 1.68 Impact Factor
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ABSTRACT: A novel compression scheme for video sequences that is robust to
fading errors in a spread spectrum environment is presented. A 3D coder
has been designed in which the sequence was decomposed into
spatio-temporal sub-bands and encoded using vector quantisation. Channel
simulation shows good image reconstruction with a PSNR of 27 dB under
the worst-case channel conditions of 18 dB
Electronics Letters 04/2000; · 0.96 Impact Factor
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ABSTRACT: An efficient soft-input-soft-output (SISO) iterative decoding
method using Kaneko's algorithm for block turbo codes (BTCs) is
proposed. Hard outputs are converted to soft-decisions using reliability
calculations. The algorithm presents a major advantage over the existing
decoding algorithms for BTCs by providing ample flexibility in terms of
performance-complexity trade-off. For any performance, the computational
complexity of the proposed algorithm is less than the computational
complexity of the similar existing algorithms. The simulation results
for the decoding algorithm for different two-dimensional BTCs over an
AWGN channel are shown
MILCOM 2000. 21st Century Military Communications Conference Proceedings; 02/2000
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ABSTRACT: Turbo codes can deliver performance that is very close to the Shannon limit. This report investigates algorithms for convolutional turbo codes and block turbo codes. Both coding schemes can achieve performance near Shannon limit. The performance of the schemes is obtained using computer simulations. There are three sections in this report. First section is the introduction. The fundamental knowledge about coding, block coding and convolutional coding is discussed. In the second section, the basic concepts of convolutional turbo codes are introduced and the performance of turbo codes, especially high rate turbo codes, is provided from the simulation results. After introducing all the parameters that help turbo codes achieve such a good performance, it is concluded that output weight distribution should be the main consideration in designing turbo codes. Based on the output weight distribution, the performance bounds for turbo codes are given. Then, the relationships between the output weight distribution and the factors like generator polynomial, interleaver and puncturing pattern are examined. The criterion for the best selection of system components is provided. The puncturing pattern algorithm is discussed in detail. Different puncturing patterns are compared for each high rate. For most of the high rate codes, the puncturing pattern does not show any significant effect on the code performance if pseudo - random interleaver is used in the system. For some special rate codes with poor performance, an alternative puncturing algorithm is designed which restores their performance close to the Shannon limit. Finally, in section three, for iterative decoding of block codes, the method of building trellis for block codes, the structure of the iterative decoding system and the calculation of extrinsic values are discussed.
10/1999;
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ABSTRACT: A computationally simple algorithm for video compression is
presented in this paper. The algorithm gives excellent quality image
sequence reconstruction at a peak-signal-to-noise-ratio (PSNR) of
approximately 37 decibels (dB) and a very low bit rate of 0.2
bits-per-pixel (bpp). The scheme utilizes absolute moment block
truncation coding (AMBTC) for intraframe coding, in conjunction with a
three step algorithm for block based motion compensation, and a simple
quantization scheme for interframe error coding. The procedural steps in
the algorithm are very similar to the MPEG standard, which can
facilitate the implementation of the proposed algorithm in the existing
infrastructure. The results of the simulations performed on three
different image sequences depicting different amounts of motion and
background activity are presented. The qualitative and quantitative
comparisons of the proposed algorithm, with an existing video
compression standard and with other similar research are presented. The
significant advantage gained in terms of computational complexity and
the probable use of the algorithm for progressive transmission of video
is illustrated. The modifications of the basic algorithm are also
presented in this paper
Military Communications Conference Proceedings, 1999. MILCOM 1999. IEEE; 02/1999
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ABSTRACT: Turbo codes have performance superior than all other coding
techniques. The main factors that make turbo codes so efficient include,
parallel concatenation structure of the encoding system, recursive
convolutional encoder, interleaver, puncturing pattern and iterative
decoding. In this research, we have investigated the effect of the
puncturing pattern on the performance of high rate turbo codes. Based on
simulation results, we claim that for most of the code rates, when a
pseudo random interleaver is applied, the selection of puncturing
pattern does not have significant effect on the code performance.
However, for some rates, a commonly used puncturing patterns does cause
much poorer performance. For these rates, a modified puncturing pattern
is proposed which restores the performance back to the Shannon limit
Military Communications Conference Proceedings, 1999. MILCOM 1999. IEEE; 02/1999
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ABSTRACT: One of the sub-systems used in on board processing for satellite channels is a Multicarrier Demodulator (MCD). The MCD consists of a demultiplexer followed by a demodulator. The demultiplexer is used to separate the frequency division multiple access signals into individual channels. The demodulator is used to bring the separated frequency division multiple access signals into baseband signals. The architecture has four modules namely a polyphase filter module, an FFT module, an interpolator network and the demodulator all operating in parallel and pipeline fashion. The VLSI implementation of a multicarrier demodulator for on-board satellite communication is presented
Circuits and Systems, 1996., IEEE 39th Midwest symposium on; 09/1996
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ABSTRACT: Intended for generated layout in embedded designs, an 11-transistor design gives one write port and three read ports. Single-sided writing and reading are done by overpowering weak feedback in the memory flip-flop's and output data latches. Transistors are scaled and layout developed to form 64-word by 16-column blocks in 0.8 μm CMOS. The four-fold decoder and I/O requirements are partially integrated into the layout
Circuits and Systems, 1996., IEEE 39th Midwest symposium on; 09/1996
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ABSTRACT: The VLSI implementation of a digital demultiplexer for on-board
satellite communication is presented. The demultiplexer is used to
separate the frequency division multiple access signals into individual
channels. The architecture has two modules namely polyphase filter
module and a FFT module operating in pipeline fashion. Architecture and
the VLSI implementation for demultiplexing 800 channels have been
developed and simulated. A module generation scheme is used that has
advantages over the full custom approach with automated generation
techniques. The module generation scheme uses a flexible cell based
design. It has an advantage of being flexible, efficient and reliable.
Various CAD tools from Mentor Graphics and 0.8 micron CMOS process from
Hewlett Packard have been used for the layout
Circuits and Systems, 1996. ISCAS '96., Connecting the World., 1996 IEEE International Symposium on; 06/1996
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ABSTRACT: Quadrature amplitude modulation schemes with modified signal
constellation are proposed. Under the peak power constraint, modified
QAM schemes can achieve a significant power gain over conventional QAM
schemes in the satellite channel
Military Communications Conference, 1995. MILCOM '95, Conference Record, IEEE; 12/1995
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ABSTRACT: One of today's problems in signal processing is the identification of direction of arrival (DOA). Many algorithms have been proposed in the literature. However, the algorithms are highly complex and require a lot of computing power. This paper presents a multiprocessor architecture that is capable of computing DOA in real time
OCEANS '95. MTS/IEEE. Challenges of Our Changing Global Environment. Conference Proceedings.; 11/1995
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ABSTRACT: An 8PSK scheme with the least significant bit (LSB) Golay coded is
proposed and its performance is analyzed. With hard decision decoding,
the proposed scheme can achieve 1 dB asymptotic coding gain and also
save 26% bandwidth, as compared with uncoded QPSK scheme
IEEE Transactions on Communications 03/1995; · 1.68 Impact Factor
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ABSTRACT: A Reed-Solomon/trellis coded concatenated (RS/TCM) scheme is investigated for a land mobile satellite system (LMSS). The inner code of the RS/TCM is a rate 2/3, 4-state TCM and the outer code is a rate 56/63 RS code. The modulation scheme used is differential 8 phase shift keying (D8PSK). Performance of this scheme is investigated by computer simulation for a vegetatively shadowed (VS) channel that typifies a satellite to mobile down-link. It is shown that the proposed RS/TCM scheme performs 4 dB better than rate 4/6, multiplicity 2, TCM (MTCM) and 10 dB better than conventional rate 2/3 TCM at a BER of 10<sup>-3 </sup>
Military Communications Conference, 1994. MILCOM '94. Conference Record, 1994 IEEE; 11/1994
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ABSTRACT: The quality of visual communications has greatly improved with
HDTV. Due to the advantages of digital communications, and the trend
towards it, it is desirable to develop a cost effective digital codec
for HDTV signals. One of the criteria in the transmission of digital
signals via satellites is the transmission bandwidth which dictates the
transmission costs. Apart from development of good compression schemes,
due consideration should also be given to the ease of hardware
implementation, which is crucial in deciding factors like processing
delay and the level of encoder/decoder complexity. With the above
mentioned factors in mind a cost-effective HDTV codec is proposed. Few
US organizations have addressed the problem of HDTV distribution via
communication satellites. The majority of efforts in the development of
an HDTV codec have been aimed at the 100 to 140 Mbits/sec data rate. To
facilitate cost effective satellite transmission, the DS3 rate of 45
Mbits/sec, is desirable. The purpose of the present research is to
compress the HDTV signals to around 20 Mbits/sec so that 2 HDTV channels
can be transmitted through the DS3 rate channel. To achieve this degree
of compression a new scheme is proposed. First subband coding is used to
decompose the image into different frequency bands. Next motion
compensation is applied to the low band, and the resulting interframe
difference is discrete cosine transform (DCT) coded. The high bands are
also DCT coded. The DCT coefficients of the difference signal of the low
band and the DCT coefficients of the high band are then vector quantized
Data Compression Conference, 1994. DCC '94. Proceedings; 04/1994
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ABSTRACT: A wideband communications satellite is designed to operate in a
satellite-only configuration for the National Research and Education
Network (NREN). On-board processing and signal regeneration are used to
increase satellite throughput and decrease satellite transmit power.
Channels supporting datagram and virtual circuit routing are provided
for lower data rate services. Dedicated channels are implemented for
higher data rate services. Satellite power, mass and cost estimates are
given. Earth station parameters and costs are also derived. A user cost
per minute is given for two different types of users
Global Telecommunications Conference, 1993, including a Communications Theory Mini-Conference. Technical Program Conference Record, IEEE in Houston. GLOBECOM '93., IEEE; 01/1994
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ABSTRACT: High-resolution direction-of-arrival (DOA) estimation is important
in many sensory systems like radars, sonars and seismic exploration.
With the advances in the area of VLSI it is now possible to design a
special purpose hardware for DOA estimation which will be suitable for
real-time sonar applications. One of the methods for DOA estimation for
broad-band sources proposed by Buckley and Griffiths [1988] has been
selected for hardware implementation. This BASS-ALE algorithm has been
simplified, parallelized and is mapped on an architecture suitable for
real time processing
OCEANS '93. Engineering in Harmony with Ocean. Proceedings; 11/1993
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ABSTRACT: All of the various research networks throughout the US are planned
to be integrated into a single, nationwide research network by the mid
1990's. This network will be the third stage of what will be called the
National Research and Education Network (NREN). A wide-band
communications satellite creates a distance insensitive link between all
users, regardless of their locations. In order to assure that a
realistic satellite is designed for the NREN, good estimates of the
network requirements are needed. This paper outlines the results of a
study performed to determine the NREN requirements
Military Communications Conference, 1993. MILCOM '93. Conference record. 'Communications on the Move'., IEEE; 11/1993
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ABSTRACT: A future National Research and Education Network (NREN) is planned to integrate all of the US research networks. A geostationary communications satellite is investigated for use with the NREN in a satellite-only configuration. Both conventional and advanced satellite designs are examined, and user costs are derived for both government and commercial system operation. The resulting costs are compared with the costs for an equivalent terrestrial network
Networks, 1993. International Conference on Information Engineering '93. 'Communications and Networks for the Year 2000', Proceedings of IEEE Singapore International Conference on; 10/1993
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ABSTRACT: The high resolution direction-of-arrival (DOA) estimation is important in many sensor systems. It is based on the processing of the received signal and extracting the desired parameters of the DOA of plane waves. Many approaches have been used for the purpose of implementing the function required for the DOA estimation. The Multiple Signal Classification (MUSIC) and the Estimation of Signal Parameters by Rotational Invariance techniques (ESPRIT) algorithms are two novel approaches used recently to provide asymptotically unbiased and efficient estimates of the DOA. They are believed to be promising and appropriate for hardware implementation for real time applications. They estimate the so called signal subspace from the array measurements. The parameters of interest (i.e. determining of the DOA) are then estimated from the intersection between the array manifold and the estimated subspace
07/1993;
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ABSTRACT: High resolution direction-of-arrival (DOA) estimation is important in many sensor systems. It is based on the processing of the received signal and extracting the desired parameters of the DOA of plane waves. The estimation of angle of arrivals of multiple broadband sources has been carried out in a variety of ways over the past few years. In this research an algorithm for broadband DOA estimation using a simple bilinear transformation matrix is investigated and a parallel and pipelined architecture is developed. When compared to other coherent approaches, this algorithm has the advantages of being non-iterative and does not require any initial estimates of the angles of arrival and all angles are computed from a single step of coherent subspace calculations. Hence it is a very suitable algorithm for computation of DOA using dedicated hardware. The advances in the area of Very Large Scale Integration (VLSI) have made it possible to design special purpose hardware which has the advantage of very high speed and overall lower system cost when compared to a system which runs off a general purpose computer.
07/1993;
