131 research outputs found

    Target localization in MIMO radar systems

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    MIMO (Multiple-Input Multiple-Output) radar systems employ multiple antennas to transmit multiple waveforms and engage in joint processing of the received echoes from the target. MIMO radar has been receiving increasing attention in recent years from researchers, practitioners, and funding agencies. Elements of MIMO radar have the ability to transmit diverse waveforms ranging from independent to fully correlated. MIMO radar offers a new paradigm for signal processing research. In this dissertation, target localization accuracy performance, attainable by the use of MIMO radar systems, configured with multiple transmit and receive sensors, widely distributed over an area, are studied. The Cramer-Rao lower bound (CRLB) for target localization accuracy is developed for both coherent and noncoherent processing. The CRLB is shown to be inversely proportional to the signal effective bandwidth in the noncoherent case, but is approximately inversely proportional to the carrier frequency in the coherent case. It is shown that optimization over the sensors\u27 positions lowers the CRLB by a factor equal to the product of the number of transmitting and receiving sensors. The best linear unbiased estimator (BLUE) is derived for the MIMO target localization problem. The BLUE\u27s utility is in providing a closed-form localization estimate that facilitates the analysis of the relations between sensors locations, target location, and localization accuracy. Geometric dilution of precision (GDOP) contours are used to map the relative performance accuracy for a given layout of radars over a given geographic area. Coherent processing advantage for target localization relies on time and phase synchronization between transmitting and receiving radars. An analysis of the sensitivity of the localization performance with respect to the variance of phase synchronization error is provided by deriving the hybrid CRLB. The single target case is extended to the evaluation of multiple target localization performance. Thus far, the analysis assumes a stationary target. Study of moving target tracking capabilities is offered through the use of the Bayesian CRLB for the estimation of both target location and velocity. Centralized and decentralized tracking algorithms, inherit to distributed MIMO radar architecture, are proposed and evaluated. It is shown that communication requirements and processing load may be reduced at a relatively low performance cost

    Target Localization Accuracy Gain in MIMO Radar Based Systems

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    This paper presents an analysis of target localization accuracy, attainable by the use of MIMO (Multiple-Input Multiple-Output) radar systems, configured with multiple transmit and receive sensors, widely distributed over a given area. The Cramer-Rao lower bound (CRLB) for target localization accuracy is developed for both coherent and non-coherent processing. Coherent processing requires a common phase reference for all transmit and receive sensors. The CRLB is shown to be inversely proportional to the signal effective bandwidth in the non-coherent case, but is approximately inversely proportional to the carrier frequency in the coherent case. We further prove that optimization over the sensors' positions lowers the CRLB by a factor equal to the product of the number of transmitting and receiving sensors. The best linear unbiased estimator (BLUE) is derived for the MIMO target localization problem. The BLUE's utility is in providing a closed form localization estimate that facilitates the analysis of the relations between sensors locations, target location, and localization accuracy. Geometric dilution of precision (GDOP) contours are used to map the relative performance accuracy for a given layout of radars over a given geographic area.Comment: 36 pages, 5 figures, submitted to IEEE Transaction on Information Theor

    Blue sky thinking : using projective techniques to stimulate discussion, reflection and insight

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    The prime purpose of this session is to share a new use of projective techniques to stimulate discussion, reflection and insight with students. The session will provide an introduction to the nature and use of projective techniques and an explanation why images of the sky were chosen as the stimuli. Then, the majority of the session will consist of an opportunity to experience this new technique in a simulated session. The session will end with a plenary discussion and a review of the effectiveness and applicability of the technique.<br /

    South West Food Community: Understanding systemic change, and its associated challenges and successes, among food security projects

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    Objective: The South West Food Community (SWFC) project (2018) aimed to identify initiatives working to support food security in the South West region of Western Australia, and to enhance how these initiatives functioned as a system. The SWFC project used a Systemic Innovation Lab approach that, prior to this study, had not been evaluated. This evaluation aimed to: i) measure system transitions (changes) to initiatives; and ii) understand the challenges and successes associated with system transitions. Methods: SWFC initiative leaders (n=46) such as directors, managers or coordinators, volunteers or committee members were invited to participate in this evaluation. Fifteen stakeholders completed the telephone interviews (32% response rate). Results: Twenty‐five desirable changes in practice were observed. Challenge and success statements determined themes of ‘participation’ and ‘bureaucracy’. Participation sub‐themes included: limited time; poor initiative attendance; community support; organisational support; and effective partnerships. Bureaucracy sub‐themes included: regulation or policy requirements; limited resources; and funding opportunities. Conclusion: The Australian‐first SWFC project has the capacity to support region‐to‐region comparisons; this evaluation increases evidence for scaling to other regions. Implications for public health: This approach can be used to increase collaboration between initiatives, support resource‐sharing between organisations and enhance policies (at local government level) to support food security

    Problems, policy and politics – perspectives of public health leaders on food insecurity and human rights in Australia

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    Background: To achieve zero hunger targets set within the United Nations’ Agenda 2030, high-income countries such as Australia must reconsider current efforts to improve food security. This study aimed to; explore perspectives from public health nutrition experts on the usefulness of drawing on the international human right to food, and associated mechanisms, to address food insecurity; identify potential roles of key stakeholders in Australia to implement a rights-based approach; and examine barriers and enablers to achieving the right to food in Australia. Methods: Qualitative in-depth interviews were conducted with key informants ( \u3e 10 years professional experience). Braun and Clarke’s (2006) six-phase approach to thematic analysis was employed to analyse data, using Kingdon’s multiple streams framework (1984) to examine interactive variables which affect policy-making processes. Results: Thirty interviews took place, with most participants representing academia (n = 16), majority had 10–14 years of experience (n = 12) and almost one quarter (n = 7) were in senior leadership roles. Participants believed that framing food insecurity as a human rights issue could be effective when communicating with some audiences, however alternative rhetoric is more popular and potentially more effective. Citizens, government, food industry, non-profit sector, research/tertiary and legal institutions were described as playing critical roles. Barriers to progress were identified as lack of awareness and acknowledgement of the problem, prioritisation of the private sector, lack of political will and domestic laws, and an inefficient/ineffective charitable food sector. Participants identified various enablers and opportunities for implementing a rights-based approach such as grass-roots advocacy efforts to raise awareness of the issue, integrating human rights into government frameworks and community projects and the political will to support action aligned with sustainable development. Conclusions: Human rights language and mechanisms have the potential to trigger genuine commitment to addressing food insecurity however should be used with caution. Australia’s public health workforce requires increased capacity to implement a human-rights approach and framing such efforts to align with sustainable development may achieve greater political action. Trial registration: Ethics approval was received from the Deakin University Human Research Ethics committee (project ID HEAG 168_2018)

    Strategies to address the complex challenge of improving regional and remote children’s fruit and vegetable consumption

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    Fruit and vegetables (F&V) are imperative for good health, yet less than one per cent of Australian children consume these food groups in sufficient quantities. As guided by Social Cognitive Theory (SCT), this paper aimed to: (i) understand key informant perspectives of the amount, types and quality of F&V consumed by rural and remote Western Australian (WA) children; and, (ii) determine strategies that could increase F&V consumption among rural and remote WA children. This qualitative study included 20 semi-structured interviews with health, school/youth and food supply workers, focusing on topics including: quantity and type of F&V consumed and strategies to increase children’s consumption. A thematic analysis was conducted using NVivo qualitative data analysis software (Version 10, 2014. QSR International Pty Ltd., Doncaster, Victoria, Australia). Key informants reported children consumed energy-dense nutrient-poor foods in place of F&V. Strategy themes included: using relevant motivators for children to increase their preference for F&V (i.e., gaming approach, SCT construct of ‘expectations’); empowering community-driven initiatives (i.e., kitchen gardens, SCT construct of ‘environment’); increasing food literacy across settings (i.e., food literacy skills, SCT construct of ‘behavioural capacity’); developing salient messages and cooking tips that resonate with parents (i.e., parent newsletters, SCT construct of ‘self-control’); increasing F&V availability, safety, and convenience (i.e., school provision); and, considering the impact of role models that extend beyond the family (i.e., relatable role models, SCT construct of ‘observational learning’). Overall, a comprehensive strategy that incorporates relevant motivators for children and families, supports local initiatives, reinforces the range of role models that are involved with children and creates healthier environments, is required to increase F&V consumption among children

    South West Food Community: How government and community initiatives are supporting systemic change towards enhanced food security

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    Objective: Food security refers to adequate physical, social and economic access to food and is regarded as a complex, ‘wicked’ issue. This research aimed to understand the perspectives of initiative leaders (stakeholders), regarding their project relating to food security and its possession of characteristics associated with system change to enhance food security. Methods: Stakeholders (n=51) participated in semi-structured interviews that evaluated initiatives (n=52) against 36 desirable characteristics for system change. Transcripts were analysed using QSR NVivo and Wicked Lab’s Tool for Systemic Change. Results: Community-based initiatives often harnessed the passion of local communities to enhance food security through awareness-raising activities and partnerships. Few initiatives created conflict to disrupt the current way of working. The largest ‘window of opportunity’ included better connection between government and community groups. Conclusions: This novel contribution provided in-depth understanding of individual initiatives and patterns of working among the food security system in the South West region of Western Australia. Implications for public health: Recommendations to better foster connection between the government and community initiatives include: ensuring government worker responsibilities include task and indicator-related measures; and strengthening understanding of food security among community groups of staff and elected member roles within local government and the ways local government could be supported to harness community knowledge. © 2020 The Author
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