-
[show abstract]
[hide abstract]
ABSTRACT: This paper presents two new open-loop synchronization algorithms for computing the satellite position. One is based on a three-rotational co-ordinate transformation, the other is based on a numerical iteration method. A detailed comparison of these two algorithms with other available algorithms is given with respect to accuracy of the computed separation distances between ground stations and the satellite, sensitivity to measurement and implementation errors, computation speed, and implementation complexity.
International Journal of Satellite Communications 03/2007; 10(2):81 - 91.
-
Pattern Recognition Letters. 01/2000; 21:1061-1069.
-
[show abstract]
[hide abstract]
ABSTRACT: A hardware implementation of an adaptive technique for reordering
of discrete cosine transform (DCT) coefficients, that are used in a
variety of transform-based image compression schemes such as JPEG, is
described. Efficient reordering is achieved for variable-size
rectangular sub-blocks using Boolean operations, that determine the
position of the next coefficient to be coded. The algorithm has been
developed for implementation in hardware using programmable logic
devices (PLDs). The implementation constitutes a Moore state machine
with binary inputs representing the number of rows and columns in the
sub-block to be reordered. Experimental results are presented which
demonstrate the potential advantages of this new technique, in terms of
a significant reduction in entropy
Image Processing and Its Applications, 1997., Sixth International Conference on; 08/1997
-
[show abstract]
[hide abstract]
ABSTRACT: A neural network technique for classification of blocks of
discrete cosine transform (DCT) coefficients using a backpropagation
algorithm is described. The DCT is employed in a variety of transform
based image compression schemes. In the authors' recent JPEG like image
compression scheme, efficient reordering of coefficients is achieved by
applying adaptive zigzag reordering to variable size rectangular sub
blocks. The additional neural network based sub block classification
discards isolated nonzero coefficients of small significance in some sub
blocks and therefore further reduces their sizes. Initial experimental
results are presented that demonstrate the potential of the additional
neural network based sub block classification in terms of improved
coding gain
Neural and Fuzzy Systems: Design, Hardware and Applications (Digest No: 1997/133), IEE Colloquium on; 06/1997
-
[show abstract]
[hide abstract]
ABSTRACT: The authors present a novel image coding technique which
explicitly aims to retain perceptually important features of the image.
The system exploits the psychovisual properties of the human visual
system, in that it identifies perceptually important vector patterns
(referred to as visual vectors) within small blocks of the image, and
codes these using a scheme similar to vector quantization (VQ). Thus the
system is referred to as visual vector quantization (VVQ). One of the
main advantages of the new VVQ scheme over traditional VQ is that it is
computationally much simpler, and yet its performance is comparable to
that of traditional VQ. Experimental results are presented which
demonstrate that the new technique can achieve visually satisfactory
image reconstruction at a compression ratio as high as 17:1. Comparison
of peak signal to noise ratio (PSNR) values shows that the performance
of the new technique is comparable to that of other VQ-based image
coders at a similar bit rate
Image Processing and its Applications, 1995., Fifth International Conference on; 08/1995
-
[show abstract]
[hide abstract]
ABSTRACT: The transmission and storage of a digital image requires
considerable expenditure in terms of bandwidth and/or memory resources.
Digital image compression is concerned with minimising the number of
bits used in representing an image, and is therefore a means of reducing
image data for economical storage or transmission. Image compression
techniques can be grouped into two broad classes: (a) lossless
techniques, and (b) lossy techniques. Some applications require lossless
compression of the image data, e.g., remote sensing, the main
application area of the work described in this paper. For multiband
satellite images redundancy exists in three forms, namely, statistical
redundancy, correlation redundancy, and interband redundancy. The
reduction of statistical redundancy and correlation redundancy within an
image has been extensively investigated by many researchers. The paper
explains that correlation redundancy was first exploited within each
band of a multiband image. A new stage exploiting interband redundancy
was then introduced. The final stage was the reduction of statistical
redundancy. Interband redundancy is quantitatively analysed, and two
schemes are developed to exploit it
Image Processing and its Applications, 1995., Fifth International Conference on; 08/1995
-
[show abstract]
[hide abstract]
ABSTRACT: The traditional fault detection and isolation techniques of the
avionics industry are rapidly becoming obsolete. To meet the modular
avionics system requirements of increased availability and reduced life
cycle costs, modules incorporating comprehensive built in self test
(BIST) capabilities are required. Only comprehensive fault detection and
isolation at component, module, sub-system and system level will enable
the criteria of fault tolerance, reconfiguration or intelligent
degradation to be achieved
Systems Design for Testability, IEE Colloquium on; 05/1995
-
International Journal of Remote Sensing 03/1995; 16(5):835-850. · 1.12 Impact Factor
-
Pattern Recognition Letters. 01/1994; 15:607-610.
-
Neural Network Applications and Tools. Workshop on (1993); 10/1993
-
[show abstract]
[hide abstract]
ABSTRACT: A Hopfield neural network based block truncation coding (BTC)
technique is presented in this paper. For this scheme, BTC is formulated
as the minimization of a cost function in which the bit map
distributions for the blocks are explicitly included. It is explained
that this cost function may also be interpreted as a measure of the
block detail. Based on the observation of the final value of the cost
function found by the Hopfield network, a block may be classified as a
high detail block or a low detail block, which are coded differently,
giving a different compression ratio for each type. It is shown that
using this new technique, compression ratios up to 7:1 with good
reconstructed image quality can be achieved. Experimental results are
presented to demonstrate the effectiveness of this new scheme
Artificial Neural Networks, 1993., Third International Conference on; 06/1993
-
[show abstract]
[hide abstract]
ABSTRACT: A new method for image compression using several multilayer perceptron (MLP) networks is described. Images to be compressed are divided into small sub-image blocks which are processed independently. The MLPs are used to code residual image blocks formed by subtracting the quantised block mean value from each pixel in the original block. To reduce edge degradation in the reconstructed images, several MLPs are used, each representing a different orientation of edge information. Simulation results are presented which demonstrate the effectiveness of this new technique.
Electronics Letters 05/1993; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The authors have developed a Hopfield (1982) neural network block
truncation coding (BTC) technique, which has been shown, in the mean
squared error sense, to improve coding performance over established BTC
techniques. A new development in using a Hopfield neural network BTC
scheme for image compression is described. Simulation results are
presented which show that the new technique provides improved coding
efficiency and maintains good visual quality in the reconstructed images
Neural Networks for Image Processing Applications, IEE Colloquium on; 11/1992
-
[show abstract]
[hide abstract]
ABSTRACT: To remove ambiguity in the information presented in the image, it is desirable to reduce its complexity to just the dominant features such as edges and homogeneous regions. The conventional techniques of image processing are an obvious starting point for such an operation and the paper assesses their effectiveness when applied to images from sensors with apertures as small as 80λ, which have just a small number of pixels per feature. The authors discuss the spatial frequency spectrum of a typical section of the image and how this relates to the low resolution of the sensor. A gradient (Sobel) operator is then demonstrated as a means of trying to reduce the image to areas of change in pixel intensity and making a first step towards a parametric representation of features within the image. A comparison is then made of the frequency spectra of two filters and the image to account for the filters' performance. They present an approach to segmentation of the image based on regional statistics and illustrate how an adaptive control of statistical parameters can result in a satisfactory segmentation. This technique also has the advantage of automatically providing a parametric representation of segmented regions and the statistical representation is readily extendable to multidimensional image data
Image Processing and its Applications, 1992., International Conference on; 05/1992
-
[show abstract]
[hide abstract]
ABSTRACT: Considerable research into the training of neural networks by the backpropagation technique has been undertaken in recent years. Introduction of a momentum term into the training equation can accelerate the training process. A new momentum step and a scheme for dynamically selecting the momentum rate are described. It is shown that these give improved acceleration of training and strong global convergence characteristics. Results are presented for four benchmark training tasks.
Electronics Letters 03/1992; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Block truncation coding (BTC), a recent technique used in the coding of image data, is based on the classification of pixels within a small image block into two classes. A new technique is introduced which uses a Hopfield neural network to define the pixel classes. Results are presented for four monochrome still images. The new algorithm is shown to provide improved performance when compared to the two previous BT algorithms.
Electronics Letters 11/1991; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Presents two new high-speed digital frame synchronisers incorporating adaptive operating strategies and postdetection processing techniques developed by the authors. These adaptive and postdetection processing frame synchronisers are shown to minimise both the false alarm probability and the misdetection probability. It is shown that the high speed can be achieved by means of time division multiplexing and a parallel implementation structure, thereby enabling low-speed integrated circuits to form the high-speed adaptive and postdetection processing frame synchronisers, which are capable of operating at bit rates as high as several hundred megabits per s.< >
Communications, Speech and Vision, IEE Proceedings I 09/1991;
-
T.J. Terrell
[show abstract]
[hide abstract]
ABSTRACT: The key points that could be addressed by lecturers engaged in DSP teaching practice at universities and polytechnics are presented. The following important considerations are discussed: students' prerequisite knowledge; course content; depth of treatment; teaching and tutorial materials; methods of presentation; knowledge consolidation and feedback; intellectual challenge; practical investigations; case studies; projects; assessment of knowledge and understanding; and curriculum development
Teaching of DSP in Universities and Polytechnics, IEE Colloquium on; 01/1991
-
Concurrency - Practice and Experience. 01/1991; 3:315-323.
-
[show abstract]
[hide abstract]
ABSTRACT: An approach to computing satellite position based on a three-dimensional
coordinate transformation is described. It is shown that the approach
results in ranging equations of reduced complexity in which neither
assumptions nor approximations are involved in the derivation of the
formulas for the satellite coordinates. Numerical examples are presented
demonstrating the accuracy of the approach, and errors in the calculated
satellite coordinates as a function of range measurement are analyzed.
An onboard open-loop ranging method for SSTDMA network synchronization
is also described. The formulation combines an onboard synchronization
concept with the conventional open-loop ranging method.
International Journal of Satellite Communications 07/1990; 8:323-332.
