Physical Sciences and Mathematics Commons^™

Unfairness And Capture Behaviour In 802.11 Adhoc Networks, C. Ware, J. Judge, Joe F. Chicharo, E. Dutkiewicz

Faculty of Informatics - Papers (Archive)

We address issues with the performance of IEEE 802.11, when used in the adhoc mode, in the presence of hidden terminals. We present results illustrating the strong dependence of channel capture behavior on the SNR observed on contending hidden connections. Experimental work has illustrated that in a hidden terminal scenario, the connection having the strongest SNR is able to capture the channel, despite the use of the RTS-CTS-DATA-ACK 4-way handshake designed to alleviate this problem. Our results indicate that the near-far SNR problem may have a significant effect on the performance of an adhoc 802.11 network.

Linear Prediction Incorporating Simultaneous Masking, J Lukasiak, I. S. Burnett, Joe F. Chicharo, M. M. Thomson

Faculty of Informatics - Papers (Archive)

Whilst linear prediction is the cornerstone of most modern speech coders, few of these coders incorporate the perceptual characteristics of hearing into the calculation of the linear predictor coefficients (LPCs). This paper proposes a method of incorporating simultaneous masking into the calculation of the LPCs. This modification requires only a modest increase in computational complexity and results in the linear predictor removing more perceptually important information from the input speech signal. This results in a filter that better models the formants of the input speech spectrum. The net effect is that an improvement in quality is achieved for a given …

The Second International Symposium On Constructing Software Engineering Tools (Coset2000), J. Gray, L. Scott, I. Ferguson

Faculty of Informatics - Papers (Archive)

No abstract provided.

Computing Running Dcts And Dsts Based On Their Second-Order Shift Properties, Jiangtao Xi, Joe F. Chicharo

Faculty of Informatics - Papers (Archive)

This paper presents a set of second-order recursive equations which are referred to as the second-order shift (SOS) properties of the discrete cosine transform (DCT) and the discrete sine transform (DST). The proposed SOS properties enable independent updating of the respective DCT and DST coefficients. This is in direct contrast with existing methodology for computing the running DCT and DST where there is an inherent interdependency between the DCT and DST coefficients. The SOS properties provide more efficient algorithms in terms of computational burden and memory requirements when implementing running DCTs and DSTs.

A New Waveform Interpolation Coding Scheme Based On Pitch Synchronous Wavelet Transform Decomposition, N. R. Chong, I. Burnett, Joe F. Chicharo

Faculty of Informatics - Papers (Archive)

This correspondence uses a pitch synchronous wavelet transform (PSWT) as an alternative characteristic waveform decomposition method for the waveform interpolation (WI) paradigm. The proposed method has the benefit of providing additional scalability in quantization than the existing WI decomposition to meet desired quality requirements. The PSWT is implemented as a quadrature mirror filter bank and decomposes the characteristic waveform surface into a series of reduced time resolution surfaces. Efficient quantization of these surfaces is achieved by exploiting their perceptual importance and inherent transmission rate requirements. The multiresolution representation has the additional benefit of more flexible parameter quantization, allowing a more …

Bounds On The Maximum Determinant For (1,-1) Matrices, C Koukouvinos, M Mitrouli, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

We suppose the Hadamard conjecture is true and an Hadamard matrix of order 4t, exists for all t ≥ 1. We use the results for the equivalent SBIBD(4t –1, 2t–1, t–1) to establish the maximum determinant or a lower bound for the maximum determinant for all ±1 matrices. In particular we give numerical results for all orders ≤100.

A New And Efficient Fail—Stop Signature Scheme, Willy Susilo, R. Safavi-Naini, M. Gysin, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

Security of ordinary digital signature schemes relies on a computational assumption. Fail-stop signature schemes provide security for a sender against a forger with unlimited computational power by enabling the sender to provide a proof of forgery, if it occurs. In this paper, we give an efficient fail-stop signature scheme that uses two hard problems, discrete logarithm and factorisation, as the basis of receiver's security. We show that the scheme has provable security against adaptively chosen message attack and is the most efficient scheme with respect to the ratio of the message length to the signature length. The scheme provides an …

Modelling Multi-Player Games Traffic, R. A. Bangun, E. Dutkiewicz

Faculty of Informatics - Papers (Archive)

The growing popularity of delay-sensitive multi-player games over the Internet is creating a need for proper characterisation of such traffic. We are currently developing source models for game traffic, on a per-player basis, with the intended use being to scale the models to simulate scenarios involving large numbers of players, which will enable us to observe the effects of game traffic on the network. We outline the procedure used, and we show that for certain cases, relatively simple source models are able to provide sufficiently accurate results (in terms of mean delay and mean buffer occupancy).

Semantic Modeling For Video Content-Based Retrieval Systems, L. A. Al Safadi, J. R. Getta

Faculty of Informatics - Papers (Archive)

This work proposes a semantic data model for video documents based on the story-line structure powerful enough to express various human interpretations of video documents, and introduces a formal query language for video retrieval that facilitates retrieval of users' heterogeneous queries based on the proposed model. The paper identifies the elementary semantic units, composite semantic units, associations and abstraction mechanisms necessary for symbolic modeling of semantic video contents. The method is independent of presentation media and it has its origins in symbolic modeling systems developed for database and complex software systems design.

Software Engineering Tools, J. Gray

Faculty of Informatics - Papers (Archive)

Automated tools play an important role in the promotion and adoption of software engineering methods and processes. The development of these tools is itself a significant software engineering task, requiring a considerable investment of time and resources. There are a large number of different kinds of automated software engineering tools, variously known as CASE, CAME, IPSE, SEE, and metaCASE tools. Although these tools differ in the particular methods, activities, and phases of the software development cycle to which they are applied, constructors of these tools often face similar implementation issues. Decisions about host computing platform, implementation language, conformance with standards …

Asymptotic Properties Of Maximum (Composite) Likelihood Estimators For Partially Ordered Markov Models, Hsin-Cheng Huang, Noel A. Cressie

Faculty of Informatics - Papers (Archive)

Partially ordered Markov models (POMMs) are Markov random fields (MRFs) with neighborhood structures derivable from an associated partially ordered set. The most attractive feature of POMMs is that their joint distributions can be written in closed and product form. Therefore, simulation and maximum likelihood estimation for the models is quite straightforward, which is not the case in general for MRF models. In practice, one often has to modify the likelihood to account for edge components; the resulting composite likelihood for POMMs is similarly straightforward to maximize. In this article, we use a martingale approach to derive the asymptotic properties of …

Minimum Phi Divergence Estimator And Hierarchical Testing In Loglinear Models, Noel A. Cressie, Leandro Pardo

Faculty of Informatics - Papers (Archive)

In this paper we consider inference based on very general divergence measures, under assumptions of multinomial sampling and loglinear models. We define the minimum phi divergence estimator, which is seen to be a generalization of the maximum likelihood estimator. This estimator is then used in a phi divergence goodness-of-fit statistic, which is the basis of two new statistics for solving the problem of testing a nested sequence of loglinear models.

Relationships Between Boolean Functions And Symmetric Groups, Chengxin Qu, Jennifer Seberry, Josef Pieprzyk

Faculty of Informatics - Papers (Archive)

We study the relations between boolean functions and symmetric groups. We consider elements of a symmetric group as variable transformations operators for boolean functions. Boolean function may be fixed or permuted by these operators. We give some properties relating the symmetric group S_n and boolean functions on V_n.

Growth In Gaussian Elimination For Weighing Matrices W(N,N-1), C. Koukouvinos, M. Mitrouli, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

We consider the values for large minors of a skew-Hadamard matrix or conference matrix W of order n and find maximum n x n minor equals to (n-1)ⁿ/₂, maximum (n-1) x (n-1) minor equals to (n-1)ⁿ/₂-1, maximum (n-2) x (n-2) minor equals 2(n-1)ⁿ/₂-2, and maximum (n-3) x (n-3) minor equals to 4(n-1)ⁿ/₂-3.

This leads us to conjecture that the growth factor for Gaussian elimination of compeletely pivoted skew-Hadamard or conference matrices and indeed any completely pivoted weighing matrix or order n and weight n-1 …

Bounds On The Maximum Determinant For (1,-1) Matrices, C. Koukouvinos, M. Mitrouli, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

We suppose the Hadamard conjecture is true and an Hadamard matrix of order 4t, exists for all t ≥ 1. We use the results for the equivalent SBIBD(4t-1,2t-1,t-1) to establish the maximum determinant or a lower bound for the maximum determinant for all ±1 matrices. In particular we give numerical results for all orders ≤100.

Exploration Of The Internet Controlled 'Rent-A-Factory' Concept, Laurence Bate, Christopher David Cook

Faculty of Informatics - Papers (Archive)

There are several robots and other devices which can now be controlled over the Internet. It is possible that an expansion of this concept ultimately leading to an Internet controlled factory could assist Australia overcome the 'tyranny' both of distance and of small production volumes. This paper discusses initial work being performed to investigate the relevance and practicality of the Internet for remote factory operations. A review of current Internet controlled equipment is presented. New experimental work involving the development of a web based graphical interface enabling clear observation and control of an Adept-One robot over the World Wide Web …

Behavioural Modelling Of High Temperature Superconducting Wires And Coils For Power Engineering Applications, Thomas Hardjono, Christopher David Cook, Sarath Perera

Faculty of Informatics - Papers (Archive)

Many aspects of the behaviour of high temperature superconducting (HTS) wires are well understood for dc applications. However, models of HTS suitable for use in circuit analysis by power engineers designing HTS applications are not readily available. This paper describes the initial development of suitable models for HTS wire. The V-I characteristics for wires carrying dc transport current can be empirically determined using a power law V=kIn. Experimentally measured V-I characteristics are fitted using the above power law. This enables the simulation of the behaviour of Bi-2223/Ag wire using the well-known circuit simulator PSpice. Other factors affecting the dc critical …

An Examination Of The Efficiency Of Australian Crop Variety Evaluation Programmes, Brian R. Cullis, A B. Smith, C Hunt, Arthur R. Gilmour

Faculty of Informatics - Papers (Archive)

In this paper we present the analysis of yield data from a broad cross-section of crop variety evaluation programmes (CVEP) conducted in Australia. The main sources of variety by environment interaction are ` non-static ' interactions, namely those linked to seasonal influences. These contributed an average of 41.3% of the total variance. In contrast the static component accounts for only 5.3% of the total.

We develop methods for determining the relative accuracy of CVEP based on selection of newly promoted entries. The accuracy of the current testing regimes for the Australian CVEP under study is determined. The accuracy of alternative …

Secure Compression Using Adaptive Huffman Coding, C. Kailasananathan, Reihaneh Safavi-Naini, Philip Ogunbona

Faculty of Informatics - Papers (Archive)

Recent developments in the Internet and Web based technologies require faster communication of multimedia data in a secure form. Standard compression algorithms such arithmetic coding schemes, and propose methods of protecting against these attacks. In the next section we review DHC, and in Section 3 describe DHC encryption scheme and examine possible attacks. In Section 4, we propose an encryption scheme that protects against the attacks and in Section 5 give the results of our experiments. Section 6, concludes the paper. as JPEG and MPEG use an entropy coding stage. By incorporating security in this stage it it possible to …

Securing Wavelet Compression With Random Permutations, Takeyuki Uehara, Reihaneh Safavi-Naini, Philip Ogunbona

Faculty of Informatics - Papers (Archive)

Wavelet compression for digital images achieves very high compression with reasonably high image quality and so is widely used in various applications. Adding security to compression algorithms has been proposed in a number of compression systems with the aim reducing the overall cost of compression and encryption. In this paper we propose a combined compression and encryption system based on wavelet transform and examine its security. Our results show that with a relatively small added cost varying degrees of security can be obtained while maintaining the performance of the compression system.

Necessary And Sufficient Conditions For Two Variable Orthogonal Designs In Order 44: Addendum, S. Georgiou, C. Koukouvinos, M. Mitrouli, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

In our recent paper Necessary and sufficient conditions for some two variable orthogonal designs in order 44, Koukouvinos, Mitrouli and Seberry leave 7 cases unresolved. Using a new algorithm given in our paper A new algorithm for computer searches for orthogonal designs by the present four authors we are able to finally resolve all these cases. This note records that the necessary conditions for the existence of two variable designs constructed using four circulant matrices are sufficient. In particular of 484 potential cases 404 cases have been found, 68 cases do not exist and 12 cases cannot be constructed using …

Strongbox Secured Secret Sharing Schemes, Jennifer Seberry, A. Penfold Street

Faculty of Informatics - Papers (Archive)

We present one way in which combinatorial designs can be used to give conditionally perfect secret sharing schemes. Schemes formed in this way have the advantage over classical secret sharing schemes of being easily adapted for use as compartmentalized or hierarchical access structures. We study the problem of completion of structures, given partial information, to obtain measures of how closely the behaviour of the secret sharing schemes approaches to ideal behaviour in practice. It may happen that part of a combinatorial design can never be reconstructed from a subset of a minimal defining set. That is, to find the blocks …

Identification Of Bad Signatures In Batches, J. Pastuszak, D. Michalek, J. Pieprzyk, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

The paper addresses the problem of bad signature identification in batch verification of digital signatures. The number of generic tests necessary to identify all bad signatures in a batch instance, is used to measure the efficiency of verifiers. The divide-and-conquer verifier DCVα(x,n) is defined. The verifier identifies all bad signatures in a batch instance x of the length n by repeatedly splitting the input into α sub-instances. Its properties are investigated. In particular, probability distributions for the number of generic tests necessary to identify one, two and three bad signatures, are derived. The average numbers of GT tests necessary to …

Homogeneous Bent Functions, C. Qu, Jennifer Seberry, J. Pieprzyk

Faculty of Informatics - Papers (Archive)

This paper discusses homogeneous bent functions. The space of homogeneous functions of degree three in six boolean variables was exhaustively searched and thirty bent functions were found. These are found to occur in a single orbit under the action of relabelling of the variables. The homogeneous bent functions identified exhibit interesting combinatorial structures and are, to the best of our knowledge, the first examples of bent functions without quadratic terms. A construction for other homogeneous bent functions of degree three in larger spaces is also given.

The Method Of Generalised Conditional Symmetries And Its Various Implementations, J. M. Goard

Faculty of Informatics - Papers (Archive)

We relate Kaptsov's method of B-determining equations for nding invariant solutions of PDEs to the nonclassical method and to the method of generalised conditional symmetries. An extension of Kaptsov's method is then used to nd new solutions of degenerate diusion equations.

A Third-Order Boussinesq Model Applied To Nonlinear Evolution Of Shallow-Water Waves, Y. L. Zhang, Song-Ping Zhu

Faculty of Informatics - Papers (Archive)

The conventional Boussinesq model is extended to the third order in dispersion and nonlinearity. The new equations are shown to possess better linear dispersion characteristics. For the evolution of periodic waves over a constant depth, the computed wave envelops are spatially aperiodic and skew. The model is then applied to the study of wave focusing by a topographical lens and the results are compared with Whalin's (1971) experimental data as well as some previous results from the conventional Boussinesq model. Encouragingly, improved agreement with Whalin's experimental data is found.

"For It Is The Number Of A Man", M. G. Michael

Faculty of Informatics - Papers (Archive)

No abstract provided.

Result Of Ac Loss Tests On Twisted And Untwisted Htsc Tape Exposed To An External Field, Tri Hardono, Christopher David Cook, Frank Darmann

Faculty of Informatics - Papers (Archive)

This paper presents the results of magnetic loss tests on twisted and untwisted 37 multifilament tapes exposed to an alternating field at power frequencies. The losses are measured using calorimetric methods, which are capable of measuring losses in short tapes with the accuracy of several microwatts per centimeter of tape. The losses of the tape due to the longitudinal field of the untwisted tape agree well with theoretical calculations. The measurement results on the twisted filament tape, with 50-mm twist pitch, show that the losses are slightly lower than that in the untwisted tape. This is due to the reduction …

Growth In Gaussian Elimination For Weighing Matrices, W (N, N — 1), C. Koukouvinos, M. Mitrouli, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

We consider the values for large minors of a skew-Hadamard matrix or conference matrix W of order n and find maximum n x n minor equals to (n — 1)n/2, maximum (n — 1) x (n — 1) minor equals to (n–1)n/2-1 maximum (n — 2) x (n — 2) minor equals to 2(n — 1) n/2–2, and maximum (n — 3) x (n — 3) minor equals to 4(n — 1)n/2-3. This leads us to conjecture that the growth factor for Gaussian elimination of completely pivoted skew-Hadamard or conference matrices and indeed any completely pivoted weighing matrix of order …

New Orthogonal Designs And Sequences With Two And Three Variables In Order 28, C. Koukouvinos, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

We give new sets of sequences with entries from {0, ±a, ±b, ±c} on the commuting variables a, b, c and zero autocorrelation function. Then we use these sequences to construct some new orthogonal de-signs. We show the necessary conditions for the existence of an OD(28; s1, s2, s3) plus the condition that (s1, s2, s3) ≠ (1,5,20) are sufficient conditions for the existence of an OD(28; s1, s2, s3). We also show the necessary conditions for the existence of an OD(28; s1, s2, s3) constructed using four circulant matrices are sufficient conditions for the existence of 4 — NPAF(s1, …