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Articles 1 - 30 of 93
Full-Text Articles in Physical Sciences and Mathematics
A Study Of Umts Turbo Codes Across Space Time Spreading Channel With The Case Of M = 1 And M = 2, I. S. Raad, Peter James Vial, Tadeusz A. Wysocki
A Study Of Umts Turbo Codes Across Space Time Spreading Channel With The Case Of M = 1 And M = 2, I. S. Raad, Peter James Vial, Tadeusz A. Wysocki
Faculty of Informatics - Papers (Archive)
The study presented in this paper is that of Universal Mobile Telecommunications Systems (UMTS) Turbo Codes across Space Time Spreading channel with one transmitter antenna, one receiver (m = 1) and two transmitter antennas and one receiver (m = 2) to see to what extent the bit error rate (BER) can be improved. Using the Max-log decoding algorithm and 12 iterations it is shown in the simulation results that an extra 5 dB is achievable.
Extending Asterism Decoding To Qam And Its Complexity In Rician Fading Mimo Systems, P. Conder, Tadeusz A. Wysocki
Extending Asterism Decoding To Qam And Its Complexity In Rician Fading Mimo Systems, P. Conder, Tadeusz A. Wysocki
Faculty of Informatics - Papers (Archive)
The area of Multiple Input Multiple Output (MIMO) communications systems has received enormous attention recently as they can provide a roughly linear increase in data rate by using Multiple Transmit and Receive antennas. The optimal detection strategy for a MIMO receiver is to perform a Maximum-Likelihood (ML) search over all possible transmitted symbol combinations has an exponential complexity when the constellation size of number of transmit antennas increase. A number of sub-optimal decoders, such as VBLAST, provide linear decoding only where the number of receive antennas is at least equal to the number of transmit antennas . Asterism decoding proposed …
Load-Balanced Route Discovery For Mobile Ad Hoc Networks, Mehran Abolhasan, Justin Lipman, Tadeusz A. Wysocki
Load-Balanced Route Discovery For Mobile Ad Hoc Networks, Mehran Abolhasan, Justin Lipman, Tadeusz A. Wysocki
Faculty of Informatics - Papers (Archive)
This paper presents Flow-Aware Routing Protocol (FARP), a new routing strategy designed to improve load balancing and scalability in mobile ad hoc networks. FARP is a hop-by-hop routing protocol, which introduces a flow-aware route discovery strategy to reduce the number of control overheads propagating through the network and distributes the flow of data through least congested nodes to balance the network traffic. FARP was implemented in Glomosim and compared with AODV. To investigate the load distribution capability of FARP new performance metrics were introduced to measure the data packet flow distribution capability of the each routing protocol. The simulation results …
Observations On The Message Integrity Code In Ieee802.11wireless Lans, Jianyong Huang, Willy Susilo, Jennifer Seberry
Observations On The Message Integrity Code In Ieee802.11wireless Lans, Jianyong Huang, Willy Susilo, Jennifer Seberry
Faculty of Informatics - Papers (Archive)
This paper surveys the security of the message integrity code used in the IEEE802.11 Wireless LANs. To address the security flaws of Wired Equivalent Privacy (WEP), the IEEE802.11i draft defines two data confidentiality and integrity protocols, Temporal Key Integrity Protocol (TKIP) and Counter-Mode-CBC-MAC Protocol (CCMP). TKIP is based on RC4, andCCMP is based on the AES cipher. TKIP includes a keyed hash functions, called Michael, as the messag integrity code. The aim of this paper is to summarise the recent research results of Michael and analyse the practicability of two attacks against Michael.
Image Quality Assessment Using A Neural Network Approach, Abdesselam Bouzerdoum, A. Havstad, A. Beghdadi
Image Quality Assessment Using A Neural Network Approach, Abdesselam Bouzerdoum, A. Havstad, A. Beghdadi
Faculty of Informatics - Papers (Archive)
In this paper, we propose a neural network approach to image quality assessment. In particular, the neural network measures the quality of an image by predicting the mean opinion score (MOS) of human observers, using a set of key features extracted from the original and test images. Experimental results, using 352 JPEG/JPEG2000 compressed images, show that the neural network outputs correlate highly with the MOS scores, and therefore, the neural network can easily serve as a correlate to subjective image quality assessment. Using 10-fold cross-validation, the predicted MOS values have a linear correlation coefficient of 0.9744, a Spearman ranked correlation …
Ontology Trend Analysis Of Dynamic Signals, David A. Stirling, P. Zulli
Ontology Trend Analysis Of Dynamic Signals, David A. Stirling, P. Zulli
Faculty of Informatics - Papers (Archive)
This paper describes a novel approach to analysing trends of a performance signal indicator from an industrial metallurgical reactor over a number of years of operation. Using a minimum message length algorithm, a detailed ontology of the signal behaviours or modalities was established. An abstraction of these yielded a number of related super states that in turn provided an insightful correspondence for the domain experts. Further detailed identification of the likely composition and causal influences contributing to each mode was subsequently induced with supervised learning.
Distributed Range Assignment For Reliable Channel Access And Reuse In Ad-Hoc Networks, G. Srivastava, P. Boustead, Joe F. Chicharo
Distributed Range Assignment For Reliable Channel Access And Reuse In Ad-Hoc Networks, G. Srivastava, P. Boustead, Joe F. Chicharo
Faculty of Informatics - Papers (Archive)
The available bandwidth in an ad-hoc network can decrease rapidly due to the shared access to the communication channel. Power control can enhance the available bandwidth by allowing non-interfering nodes to communicate simultaneously. A number of power aware topology control algorithms have been proposed, where low power transmissions are used to forward duta. However, evaluating the power level for the data packets is not sufficient. Reliable transmission of the data packets in a shared channel network requires a number of signalling messages at the Medium Access Channel (MAC) layer. The trmsmission power of the signalling messages is crucial for both …
Accuracy Limitations Introduced By Digital Projection Sources In Profilometric Optical Metrology Systems, Matthew J. Baker, Joe F. Chicharo, Jiangtao Xi, Enbang Li
Accuracy Limitations Introduced By Digital Projection Sources In Profilometric Optical Metrology Systems, Matthew J. Baker, Joe F. Chicharo, Jiangtao Xi, Enbang Li
Faculty of Informatics - Papers (Archive)
The accuracy of profilometric optical metrology systems utilising Digital Fringe Projection (DFP) is analysed. An analytical model to describe theoretical accuracy limitation is derived and given as a function of object distance from the projector, projector resolution, projection angle and also object gradient. Associated limitations of the model are also discussed and analysed. The validity of the new model is demonstrated through practical experimentation.
Measuring Multiple Parameters In A Self-Mixing Optical Feedback System, Yanguang Yu, Jiangtao Xi, Enbang Li, Joe F. Chicharo, Thierry Bosch
Measuring Multiple Parameters In A Self-Mixing Optical Feedback System, Yanguang Yu, Jiangtao Xi, Enbang Li, Joe F. Chicharo, Thierry Bosch
Faculty of Informatics - Papers (Archive)
We propose a new approach that yields the values of multiple parameters at the same time for self-mixing optical feedback interferometric systems. These parameters are the linewidth enhancement factor of Semiconductor Lasers, the optical feedback level factor as well as vibration information of a target including the frequency and the amplitude. The method is based on optical feedback interferometry. Its effectiveness has been confirmed by computer simulations and experiments.
A Calibration Approach For Decoupling Colour Cross-Talk Using Nonlinear Blind Signal Separation Network, Y. Hu, Jiangtao Xi, Enbang Li, Joe F. Chicharo, Zongkai Yang, Yuanguang Yu
A Calibration Approach For Decoupling Colour Cross-Talk Using Nonlinear Blind Signal Separation Network, Y. Hu, Jiangtao Xi, Enbang Li, Joe F. Chicharo, Zongkai Yang, Yuanguang Yu
Faculty of Informatics - Papers (Archive)
We present a calibration approach to invert the nonlinear mixing process of colour cross-talk in multi-channel profilometry systems. Parameters of the inverse network are determined by a nonlinear blind signal separation algorithm. Experimental and simulation results demonstrate that proposed approach can effectively reduce colour leakages and improve the measurement accuracy.
Role Of Wavelet Transforms In Image Restoration, Prashan Premaratne, I. Burnett
Role Of Wavelet Transforms In Image Restoration, Prashan Premaratne, I. Burnett
Faculty of Informatics - Papers (Archive)
Image processing techniques including image restoration rely heavily on discrete Fourier transform (DFT) for frequency domain representation for analysis of its frequency content. Even though wavelet analysis has been around for more than a decade, much of its potential as a tool to analyze time-frequency localization of signal has not been properly tapped. In blind iterative deconvolution where a degraded image is restored with minimum a priori information about the original image or the point spread function (PSF), it is almost impossible to evaluate whether a restoration is achieved or not without human observation. We propose a new approach using …
Topology Control In Heterogeneous Ad-Hoc Networks, G. Srivastava, P. Boustead, Joe F. Chicharo
Topology Control In Heterogeneous Ad-Hoc Networks, G. Srivastava, P. Boustead, Joe F. Chicharo
Faculty of Informatics - Papers (Archive)
Topology control in an ad-hoc network can provide better spatial reuse of the wireless channel and conserve power. Topology construction and maintenance is a challenging issue. A number of distributed topology control algorithms have been proposed to remove the need of a centralised controller. Distributed algorithms such as location information no topology (LINT), location information link state topology (LILT) and mobile-grid (MG), aim to achieve overall network connectivity and low transmission range by maintaining a minimum node degree value. In the case of a non-uniform node distribution, maintaining a minimum node degree can unnecessarily partition a network. In this paper, …
Online Bandwidth Auctions For Efficient Allocation Of Bandwidth, Ying Peng Que, D. Platt
Online Bandwidth Auctions For Efficient Allocation Of Bandwidth, Ying Peng Que, D. Platt
Faculty of Informatics - Papers (Archive)
This paper describes an on-line auction process for dynamic bandwidth allocation in communication networks. The auction is intended to be repeated at short (perhaps ten minute) intervals. The outcome of the auction gives both the bandwidth allocation, and the price to be paid for it. The network is assumed to be MPLS capable, and two variations are provided, one in which a single LSP is available between each source/destination pair, and another in which multiple LSPs are available. We show that the present algorithms are scalable up to about 150 nodes.
The Price We Pay For Using Tcp, D. King, K. Walker, D. Platt
The Price We Pay For Using Tcp, D. King, K. Walker, D. Platt
Faculty of Informatics - Papers (Archive)
This paper examines a hop-by-hop flow control scheme and compares it with the operation of TCP end-to-end flow control. The individual link control scheme is described. Both schemes are simulated under bursty traffic in a network with 50 nodes and 96 links. It is found that the hop-by-hop scheme results in similar levels of utilization to TCP, but that the average queue size is 30 times smaller.
Don't Do What Australia Has Done, R. Nillsen
Don't Do What Australia Has Done, R. Nillsen
Faculty of Informatics - Papers (Archive)
The paper describes and analyses the environment in Australian universities since the changes initiated under the Labor government in 1988 by John Dawkins. It looks at the role and interplay of ideas in the changing intellectual culture in universities, in particular the common effect of the ideas of both liberal economics and postmodernism, and the tensions between corporate values and open enquiry. It raises the issues of the extent to which universities should have a distinct set of values from wider society, and the basis upon which universities should exist as distinctive institutions.
Weighted Segmented Digital Watermarking, Glen Wheeler, R. Safavi-Naini, N. P. Sheppard
Weighted Segmented Digital Watermarking, Glen Wheeler, R. Safavi-Naini, N. P. Sheppard
Faculty of Informatics - Papers (Archive)
We introduce the notion of weighted watermarking for proof-of-ownership watermark protection of multimedia works that are the product of more than one author and where each author is considered to be of different importance relative to the other authors. We specifically examine weighted segmented watermarking for still images and generalise previous work on performance measurement of watermark embedding patterns in the presence of cropping attacks.
Import/Export In Digital Rights Management, R. Safavi-Naini, N. P. Sheppard, Takeyuki Uehara
Import/Export In Digital Rights Management, R. Safavi-Naini, N. P. Sheppard, Takeyuki Uehara
Faculty of Informatics - Papers (Archive)
The inherently controlled nature of digital rights management systems does little to promote inter-operability of systems provided by different vendors. In this paper, we consider import and export functionality by which multimedia protected by one digital rights management regime can be made available to a multimedia device that supports a different digital rights management regime, without compromising the protection afforded to the content under the original regime. We first identify specific issues to be addressed by developers of digital rights management import/export regimes and outline a variety of methods by which these regimes may be implemented. We then apply our …
Image Database Retrieval Using Sketched Queries, A. Chalechale, G. Naghdy, Prashan Premaratne
Image Database Retrieval Using Sketched Queries, A. Chalechale, G. Naghdy, Prashan Premaratne
Faculty of Informatics - Papers (Archive)
This paper presents a novel approach for sketch-based image retrieval based on low-level features. It enables the measuring of the similarity among full color multi-component images within a database (models) and simple black and white user sketched queries. It needs no cost intensive image segmentation. Strong edges of the model image and morphologically thinned version of the query image are used for image abstraction. Angular-radial decomposition of pixels in the abstract images is used to extract new compact and affine invariant features. Comparative results, employing an art database (ArT BANK), show significant improvement in average normalized modified retrieval rank (ANMRR) …
De-Cumulant Based Approaches For Convolutive Blind Source Separation, T. Mei, Jiangtao Xi, Joe F. Chicharo, F. Yin
De-Cumulant Based Approaches For Convolutive Blind Source Separation, T. Mei, Jiangtao Xi, Joe F. Chicharo, F. Yin
Faculty of Informatics - Papers (Archive)
This paper studies the blind separation of signal sources (BSS) based on the approach of de-cumulant. It considers the cases where independent signal sources are mixed through convolutive mixing system with unity autochannel frequency responses and causal cross-channel FIR filters. Firstly, it tries to show that the de-cumulant is sufficient for separation. Secondly, novel algorithms are developed based on zero-forcing of cross-cumulant pairs. These algorithms are developed in the time-domain and so there is not the frequency permutation ambiguity problem usually suffered by most of the frequency-domain algorithms. Simulation results are presented to support the validity of the proposed algorithms.
Decorrelation: Sufficient For Convolutive Blind Source Separation?, Jiangtao Xi, T. Mei, Joe F. Chicharo, F. Yin
Decorrelation: Sufficient For Convolutive Blind Source Separation?, Jiangtao Xi, T. Mei, Joe F. Chicharo, F. Yin
Faculty of Informatics - Papers (Archive)
This paper considers blind separation of signal sources in a convolutive mixing environment. It tries to show that decorrelation is sufficient for separation of convolutively mixed sources. Two algorithms are also proposed and tested by computer simulations.
Blur Retrieval Via Separation Of Zeros Sheets From Noisy Blurred Images, Prashan Premaratne, I. Burnett, C. D. Liyanage
Blur Retrieval Via Separation Of Zeros Sheets From Noisy Blurred Images, Prashan Premaratne, I. Burnett, C. D. Liyanage
Faculty of Informatics - Papers (Archive)
A novel method of separating the point spread function from blurred images using zeros of the Z transform is presented when more than one blurred image is available. The proposed method is demonstrated to be effective with significant contamination with signal-to-noise ratios of over 30 dB. This method holds much promise as a blind deconvolution (i.e. problem of recovering two functions from their convolution) technique, as it does not impose any constraints on the point spread function, such as positivity. The article is presented with experimental results over different signal-to-noise ratios, depicting its effectiveness as a practical image restoration technique.
Power Quality Waveform Generator Based On The Csound Software Sound Synthesizer, J. P. Braun, V. J. Gosbell, S. Perera
Power Quality Waveform Generator Based On The Csound Software Sound Synthesizer, J. P. Braun, V. J. Gosbell, S. Perera
Faculty of Informatics - Papers (Archive)
Power quality investigations in the laboratory often require waveform generators capable of recreating the various disturbances present in an electrical system. These sources of waveforms are generally based on arbitrary waveform generators (AWG) because of the great flexibility they offer. However, AWGs are generally not well suited for time varying waveforms because of the limited size of their memory. To circumvent this limitation, a real time waveform synthesizer is required, but their applicability is generally limited by cost. This paper presents the use of CSound, a software sound synthesizer to achieve this aim in a cost effective manner. This paper …
Primary And Secondary Indices For Power Quality (Pq) Survey Reporting, V. J. Gosbell, S. Perera, Robert A. Barr, Alex Baitch
Primary And Secondary Indices For Power Quality (Pq) Survey Reporting, V. J. Gosbell, S. Perera, Robert A. Barr, Alex Baitch
Faculty of Informatics - Papers (Archive)
Routine monitoring involves many PQ monitors at fixed sites with readings able to be interrogated remotely and downloaded to a central database. The amount of data for one year is large, and innovative methods are needed to ensure that it can give useful insights. Primary indices are proposed to show whether a site is acceptable to specified standards and are mainly based on 95% values. Secondary indices are proposed to give additional insights. For variations, indices are proposed to give a measure of the impact on customer equipment beyond that incorporated in standards. Sag secondary indices are defined to give …
Benchmarking Utilities For The Impact Of Voltage Sags On Customers, H. M. Herath, V. J. Gosbell, S. Perera
Benchmarking Utilities For The Impact Of Voltage Sags On Customers, H. M. Herath, V. J. Gosbell, S. Perera
Faculty of Informatics - Papers (Archive)
Most utilities have increased their focus on voltage sags as the sags account for vast majority of recorded equipment trips. Although these events are not necessarily the most frequent, they have a tremendous economic impact on end-users. The process of benchmarking customer voltage sag levels generally requires voltage sag monitoring data for a period of minimum one year. This data can then be quantified to relate voltage sag performance with standardized limits for acceptable performance. This work suggests a methodology for benchmarking the impact of voltage sags on customers of different utilities by means of a three stage reporting procedure …
Computation Of The Free Distance And Low Weight Distribution Of Turbo Codes With Convolutional Interleavers, Sina Vafi, Tadeusz A. Wysocki
Computation Of The Free Distance And Low Weight Distribution Of Turbo Codes With Convolutional Interleavers, Sina Vafi, Tadeusz A. Wysocki
Faculty of Informatics - Papers (Archive)
This work presents an algorithm for computation of the free distance parameter of turbo codes with a convolutional interleaver implemented to act as a block interleaver. Based on the properties of the interleaver and the algorithm applied, we can also determine the other low weights of turbo codes and this is useful in determining the performance of the error floor of turbo codes. For different turbo code structures, the relevant parameters have been computed. The error rate simulations confirm the algorithm results.
A Scalable And Oblivious Digital Watermarking For Images, W. Lu, R. Safavi-Naini, Takeyuki Uehara, Wanqing Li
A Scalable And Oblivious Digital Watermarking For Images, W. Lu, R. Safavi-Naini, Takeyuki Uehara, Wanqing Li
Faculty of Informatics - Papers (Archive)
Scalable compression algorithms, such as JPEG, can compress images to different quality or resolution levels so that the target systems with different display capabilities, can display the image. Digital watermarking is widely used for protection of copyright and identification of ownership on digital images. It is desirable to have scalable watermarking systems, where the watermark is detectable when the watermarked image is at low quality or low resolution levels. This paper presents an oblivious block-based spread-spectrum-like watermarking system which is robust against scalable JPEG compression, cropping and shifting. The system is secure against the common watermarking attacks. Experimental results support …
A Semi-Supervised Map Segmentation Of Brain Tissues, Wanqing Li, C. Desilver, Y. Attikiouzel
A Semi-Supervised Map Segmentation Of Brain Tissues, Wanqing Li, C. Desilver, Y. Attikiouzel
Faculty of Informatics - Papers (Archive)
This paper presents a method for semi-supervised MAP (maximum a-posterior probability) segmentation of brain tissues where labelled data are available for either all types of tissues or only a few types of tissues possibly at different levels of quality. The proposed MAP segmentation takes supervised and unsupervised segmentation as its two special cases where, respectively, quality labelled data is available or there is no labelled data at all. Experiments on real MR images have shown that the proposed method improved the segmentation accuracy substantially with only a few labelled data in comparison with both fully supervised method with the same …
Space Time Spreading With Modified Walsh-Hadamard Sequences, Peter James Vial, Beata J. Wysocki, I. Raad, Tadeusz A. Wysocki
Space Time Spreading With Modified Walsh-Hadamard Sequences, Peter James Vial, Beata J. Wysocki, I. Raad, Tadeusz A. Wysocki
Faculty of Informatics - Papers (Archive)
Previous work has shown that the performance of a space time spreading (STS) system using Walsh codes with two transmit antennas at the base station (BS) is degraded in the presence of mutual interference from adjacent sectors in the same cell. We use modified Walsh-Hadamard sequences exhibiting improved cross-correlation performance, which potentially mitigates the effects of MAI (multiple access interference). The presented study also looks at variation of sets of different modified Walsh-Hadamard codes being used by the adjacent interferer, with a hundred randomly selected pairings being chosen, as well as the case where one set of alternate codes is …
Distributed, Collaborative Learning Environments Using Ad Hoc Networks, A. Fuller, Penelope Mcfarlane, D. F. Saffioti
Distributed, Collaborative Learning Environments Using Ad Hoc Networks, A. Fuller, Penelope Mcfarlane, D. F. Saffioti
Faculty of Informatics - Papers (Archive)
Computer assisted distributed or collaborative learning environments have been in existence for some time, however one impediment to more widespread use has been the need for a permanent wired network infrastructure. In this paper we discuss the development of a prototype tool that allows the formation of an ad hoc network at any time, and in any locale.
Living With Inconsistencies In A Multidatabase System, J. R. Getta
Living With Inconsistencies In A Multidatabase System, J. R. Getta
Faculty of Informatics - Papers (Archive)
Integration of autonomous sources of information is one of the most important problems in implementation of the global information systems. This paper considers multidatabase systems as one of the typical architectures of global information services and addresses a problem of storing and processing inconsistent information in such systems. A new data model proposed in the paper separates sure from inconsistent information and introduces a system of elementary operations on the containers with sure and inconsistent information. A review of the implementation aspects in an environment of a typical relational database management system concludes the paper.