Spectrum sensing, detection and optimisation in cognitive radio for non-stationary primary user signals

Cognitive radio is an emerging technology proposing the concept of dynamic spec- trum access as a solution to the looming problem of spectrum scarcity caused by the growth in wireless communication systems. Under the proposed concept, non- licensed, secondary users (SU) can access spectrum owned by licensed, primary users (PU) so long as interference to PU are kept minimal. Spectrum sensing is a crucial task in cognitive radio whereby the SU senses the spectrum to detect the presence or absence of any PU signal. Conventional spectrum sensing assumes the PU signal as ‘stationary’ and remains in the same activity state during the sensing cycle, while an emerging trend models PU as ‘non-stationary’ and undergoes state changes. Existing studies have focused on non-stationary PU during the transmission period, however very little research considered the impact on spectrum sensing when the PU is non-stationary during the sensing period. The concept of PU duty cycle is developed as a tool to analyse the performance of spectrum sensing detectors when detecting non-stationary PU signals. New detectors are also proposed to optimise detection with respect to duty cycle ex- hibited by the PU. This research consists of two major investigations. The first stage investigates the impact of duty cycle on the performance of existing detec- tors and the extent of the problem in existing studies. The second stage develops new detection models and frameworks to ensure the integrity of spectrum sensing when detecting non-stationary PU signals. The first investigation demonstrates that conventional signal model formulated for stationary PU does not accurately reflect the behaviour of a non-stationary PU. Therefore the performance calculated and assumed to be achievable by the conventional detector does not reflect actual performance achieved. Through analysing the statistical properties of duty cycle, performance degradation is proved to be a problem that cannot be easily neglected in existing sensing studies when PU is modelled as non-stationary. The second investigation presents detectors that are aware of the duty cycle ex- hibited by a non-stationary PU. A two stage detection model is proposed to improve the detection performance and robustness to changes in duty cycle. This detector is most suitable for applications that require long sensing periods. A second detector, the duty cycle based energy detector is formulated by integrat- ing the distribution of duty cycle into the test statistic of the energy detector and suitable for short sensing periods. The decision threshold is optimised with respect to the traffic model of the PU, hence the proposed detector can calculate average detection performance that reflect realistic results. A detection framework for the application of spectrum sensing optimisation is proposed to provide clear guidance on the constraints on sensing and detection model. Following this framework will ensure the signal model accurately reflects practical behaviour while the detection model implemented is also suitable for the desired detection assumption. Based on this framework, a spectrum sensing optimisation algorithm is further developed to maximise the sensing efficiency for non-stationary PU. New optimisation constraints are derived to account for any PU state changes within the sensing cycle while implementing the proposed duty cycle based detector.

Defining and describing what we do : doctrinal legal research

The practitioner lawyer of the past had little need to reflect on process. The doctrinal research methodology developed intuitively within the common law — a research method at the core of practice. There was no need to justify or classify it within a broader research framework. Modern academic lawyers are facing a different situation. At a time when competition for limited research funds is becoming more intense, and in which interdisciplinary work is highly valued and non-lawyers are involved in the assessment of grant applications, lawyer-applicants who engage in doctrinal research need to be able to explain their methodology more clearly. Doctrinal scholars need to be more open and articulate about their methods. These methods may be different in different contexts. This paper examines the doctrinal method used in legal research and its place in recent research dialogue. Some commentators are of the view that the doctrinal method is simply scholarship rather than a separate research methodology. Richard Posner even suggests that law is ‘not a field with a distinct methodology, but an amalgam of applied logic, rhetoric, economics and familiarity with a specialized vocabulary and a particular body of texts, practices, and institutions ...’.1 Therefore, academic lawyers are beginning to realise that the doctrinal research methodology needs clarification for those outside the legal profession and that a discussion about the standing and place of doctrinal research compared to other methodologies is required.

The Impact of Indigenous status on adult sentencing : a review of the statistical research literature.

The gross overrepresentation of Indigenous peoples in prison populations suggests that sentencing may be a discriminatory process. Using findings from recent (1991–2011) multivariate statistical sentencing analyses from the United States, Canada, and Australia, we review the 3 key hypotheses advanced as plausible explanations for baseline sentencing discrepancies between Indigenous and non-Indigenous adult criminal defendants: (a) differential involvement, (b) negative discrimination, and (c) positive discrimination. Overall, the prior research shows strong support for the differential involvement thesis and some support for the discrimination theses (positive and negative). We argue that where discrimination is found, it may be explained by the lack of a more complete set of control variables in researchers’ multivariate models and/or differing political and social contexts.

Understanding injury-related disability in non-Western societies can contribute to more effective road safety policies and programs

• Road crashes as a cause of disability • Disability in the study of road safety • Thai spinal injury study – Contextual information – beliefs and community – Transport system and hidden safety costs – Cambodia experience – Pakistan fatalism study • Feedback to policies and programs

Non-parametric techniques for fast and robust stereo matching

The mining environment presents a challenging prospect for stereo vision. Our objective is to produce a stereo vision sensor suited to close-range scenes consisting mostly of rocks. This sensor should produce a dense depth map within real-time constraints. Speed and robustness are of foremost importance for this application. This paper compares a number of stereo matching algorithms in terms of robustness and suitability to fast implementation. These include traditional area-based algorithms, and algorithms based on non-parametric transforms, notably the rank and census transforms. Our experimental results show that the rank and census transforms are robust with respect to radiometric distortion and introduce less computational complexity than conventional area-based matching techniques.

Suitability of non-parametric stereo matching algorithms for mining automation

The mining environment, being complex, irregular and time varying, presents a challenging prospect for stereo vision. For this application, speed, reliability, and the ability to produce a dense depth map are of foremost importance. This paper assesses the suitability of a number of matching techniques for use in a stereo vision sensor for close range scenes consisting primarily of rocks. These include traditional area-based matching metrics, and non-parametric transforms, in particular, the rank and census transforms. Experimental results show that the rank and census transforms exhibit a number of clear advantages over area-based matching metrics, including their low computational complexity, and robustness to certain types of distortion.

Frame-rate stereopsis using non-parametric transforms and programmable logic

A frame-rate stereo vision system, based on non-parametric matching metrics, is described. Traditional metrics, such as normalized cross-correlation, are expensive in terms of logic. Non-parametric measures require only simple, parallelizable, functions such as comparators, counters and exclusive-or, and are thus very well suited to implementation in reprogrammable logic.

Non-invasive identification of proteoglycans and chondrocyte differentiation state by Raman microspectroscopy

Proteoglycans (PGs) are crucial extracellular matrix (ECM) components that are present in all tissues and organs. Pathological remodeling of these macromolecules can lead to severe diseases such as osteoarthritis or rheumatoid arthritis. To date, PG-associated ECM alterations are routinely diagnosed by invasive analytical methods. Here, we employed Raman microspectroscopy, a laser-based, marker-free and non-destructive technique that allows the generation of spectra with peaks originating from molecular vibrations within a sample, to identify specific Raman bands that can be assigned to PGs within human and porcine cartilage samples and chondrocytes. Based on the non-invasively acquired Raman spectra, we further revealed that a prolonged in vitro culture leads to phenotypic alterations of chondrocytes, resulting in a decreased PG synthesis rate and loss of lipid contents. Our results are the first to demonstrate the applicability of Raman microspectroscopy as an analytical and potential diagnostic tool for non-invasive cell and tissue state monitoring of cartilage in biomedical research. ((c) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).

Writing and publishing research articles in teams

This paper provides insight into writing scholarly research articles by working collaboratively in teams. Collaborative writing is increasingly common practice within organizational and university contexts. While there is a growing volume of literature which examines various aspects of collaborative writing from challenges to politics, less attention is paid to practical aspects of how to write in teams, particularly within the context of research training. The article examines practical approaches to collaborative writing, and delineates primary continuities and disjunctions between ‘traditional collaboration’ relying largely upon physical face-to-face meetings, and ‘virtual teams’ which are geographically or organizationally dispersed and communicate via virtual, mobile, online or telephony enabled communication.

The Empty City (playreading)

This 45 minute non-verbal intermedial performance for children was adapted from the picture book I authored of the same name. The process involved writing and re-writing text and music with the result being a new draft of both script and soundtrack. Part of the judging process for the award the script was nominated for involved a playreading, which offered a particular challenge to the researcher in terms of composition and playwriting. How can a script and soundtrack for a non-verbal, intermedial work adapt and innovate the within the formal and practical constraints of the traditional ‘playreading’? This project’s emphasis on nestling intermediality within ostensibly traditional theatrical constraints and processes draws on concepts of musicalisation, identified by Varopolou. (in Lehmann 2006:91) Certain ‘musical moments’ in the piece echoed Ross Brown’s (2010) acoustemological concepts of sonification of everyday life, and the process involved dynamic curation of ‘music under’ for emotional effect, avoiding cinematic clichés and reaching for connections between music and emotion characterized by scholars such as Juslin and Sloboda (2001) The resulting performance was a hybrid of playreading and slideshow, supported by an original soundtrack of ‘music under’ (pre-recorded, but ‘DJ’ed’ live) as well as text-driven moments where music and sound were foregrounded. Research contribution This iteration of The Empty City shows that the tradition of the playreading can be a playful space where even the multiple layers of an intermedial performance text can be represented. The Empty City was a finalist in the 2012-13 Queensland Premier’s Drama Award. A ticketed public playreading of the script was held in the Queensland Theatre Company’s Bille Brown Studio on the 28th of July 2012 alongside the other finalists.

Managing intravenous medications in the non-hospital setting: An ethnographic investigation

Little published information exists about the issues involved in conducting complex intravenous medication therapy in patients' homes. An ethnographic study of a local hospital-in-the-home program in the Australian Capital Territory explored this phenomenon to identify those factors that had an impact on the use of medicine in the home environment. This article focuses on one of the three themes identified in the study-Clinical Practice. Within this theme, topics related to the organization and management of intravenous medications, geography and diversity of patient caseload, and communication in the practice setting are discussed. These findings have important implications for policy development and establishment of a research agenda for hospital-in-the-home services.

Mobile valuations : the Internet's impact on traditional valuation services

Preparing valuations is a time consuming process involving site inspections, research and report formulation. The ease of access to the internet has changed how and where valuations may be undertaken. No longer is it necessary to return to the office to finalise reports, or leave your desk in order to undertake research. This enables more streamlined service delivery and is viewed as a positive. However, it is not without negative impacts. This paper seeks to inform practitioners of the work environment changes flowing from increased access to the internet. It identifies how increased accessibility to, and use of, technology and the internet has, and will continue to, impact upon valuation service provision into the future.

A qualitative study of the determinants of dieting and non-dieting approaches in overweight/obese Australian adults.

Background Dieting has historically been the main behavioural treatment paradigm for overweight/obesity, although a non-dieting paradigm has more recently emerged based on the criticisms of the original dieting approach. There is a dearth of research contrasting why these approaches are adopted. To address this, we conducted a qualitative investigation into the determinants of dieting and non-dieting approaches based on the perspectives and experiences of overweight/obese Australian adults. Methods Grounded theory was used inductively to generate a model of themes contrasting the determinants of dieting and non-dieting approaches based on the perspectives of 21 overweight/obese adults. Data was collected using semi-structured interviews to elicit in-depth individual experiences and perspectives. Results Several categories emerged which distinguished between the adoption of a dieting or non-dieting approach. These categories included the focus of each approach (weight/image or lifestyle/health behaviours); internal or external attributions about dieting failure; attitudes towards established diets, and personal autonomy. Personal autonomy was also influenced by another category; the perceived knowledge and self-efficacy about each approach, with adults more likely to choose an approach they knew more about and were confident in implementing. The time perspective of change (short or long-term) and the perceived identity of the person (fat/dieter or healthy person) also emerged as determinants of dieting or non-dieting approaches respectively. Conclusions The model of determinants elicited from this study assists in understanding why dieting and non-dieting approaches are adopted, from the perspectives and experiences of overweight/obese adults. Understanding this decision-making process can assist clinicians and public health researchers to design and tailor dieting and non-dieting interventions to population subgroups that have preferences and characteristics suitable for each approach.