500 research outputs found

    Wireless local area network planning: an overview

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    When planning a wireless local area network, there are design issues that need to be considered. In this paper, the fundamentals of planning a wireless local area network are introduced and discussed to highlight the requirements involved. Network constraints, as their relevance to wireless network design is investigated. The paper concludes with an overview of wireless network planning solutions including commercial and free software, and an introduction to the author’s research

    Development of wireless network planning software for rural community use

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    Rural New Zealand has poor access to broadband Internet. The CRCnet project at the University of Waikato identified point-to-point wireless technology as an appropriate solution, and built networks for rural communities. The project identified viable solutions using low-cost wireless technologies and commodity hardware, allowing them to establish general construction guidelines for planning rural wireless networks. The CRCnet researchers speculated that these general construction guidelines had simplified the wireless network problem to a point at which it seemed feasible to embed the guidelines within a software tool. A significant observation by the CRCnet researchers was that community members are collectively aware of much of the local information that is required in the planning process. Bringing these two ideas together, this thesis hypothesises that a software tool could be designed to enable members of rural communities to plan their own wireless networks. To investigate this hypothesis, a wireless network planning system (WiPlan) was developed. WiPlan includes a tutorial that takes the unique approach of teaching the user process rather than the detail of network planning. WiPlan was evaluated using a novel evaluation technique structured as a roleplaying game. The study design provided participants with local knowledge appropriate for their planning roles. In two trials, WiPlan was found to support participants in successfully planning feasible networks, soliciting local knowledge as needed throughout the planning process. Participants in both trials were able to use the techniques introduced by the tutorial while planning their wireless network and successfully plan feasible wireless networks within budget in both study trials. This thesis explores the feasibility of designing a wireless networking planning tool, that can assist members of rural communities with no expertise in wireless network planning, to plan a feasible network and provides reasonable evidence to support the claim that such a planning tool is feasible

    Maternal and fetal genetic effects on birth weight and their relevance to cardio-metabolic risk factors.

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    Birth weight variation is influenced by fetal and maternal genetic and non-genetic factors, and has been reproducibly associated with future cardio-metabolic health outcomes. In expanded genome-wide association analyses of own birth weight (n = 321,223) and offspring birth weight (n = 230,069 mothers), we identified 190 independent association signals (129 of which are novel). We used structural equation modeling to decompose the contributions of direct fetal and indirect maternal genetic effects, then applied Mendelian randomization to illuminate causal pathways. For example, both indirect maternal and direct fetal genetic effects drive the observational relationship between lower birth weight and higher later blood pressure: maternal blood pressure-raising alleles reduce offspring birth weight, but only direct fetal effects of these alleles, once inherited, increase later offspring blood pressure. Using maternal birth weight-lowering genotypes to proxy for an adverse intrauterine environment provided no evidence that it causally raises offspring blood pressure, indicating that the inverse birth weight-blood pressure association is attributable to genetic effects, and not to intrauterine programming.The Fenland Study is funded by the Medical Research Council (MC_U106179471) and Wellcome Trust

    Crowdsourcing hypothesis tests: Making transparent how design choices shape research results

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    To what extent are research results influenced by subjective decisions that scientists make as they design studies? Fifteen research teams independently designed studies to answer fiveoriginal research questions related to moral judgments, negotiations, and implicit cognition. Participants from two separate large samples (total N > 15,000) were then randomly assigned to complete one version of each study. Effect sizes varied dramatically across different sets of materials designed to test the same hypothesis: materials from different teams renderedstatistically significant effects in opposite directions for four out of five hypotheses, with the narrowest range in estimates being d = -0.37 to +0.26. Meta-analysis and a Bayesian perspective on the results revealed overall support for two hypotheses, and a lack of support for three hypotheses. Overall, practically none of the variability in effect sizes was attributable to the skill of the research team in designing materials, while considerable variability was attributable to the hypothesis being tested. In a forecasting survey, predictions of other scientists were significantly correlated with study results, both across and within hypotheses. Crowdsourced testing of research hypotheses helps reveal the true consistency of empirical support for a scientific claim.</div

    The efficacy of path loss models for fixed rural wireless links

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    In this paper we make use of a large set of measurements from a production wireless network in rural New Zealand to analyze the performance of 28 path loss prediction models, published over the course of 60 years. We propose five metrics to determine the performance of each model. We show that the state of the art, even for the “simple” case of rural environments, is surprisingly ill-equipped to make accurate predictions. After combining the best elements of the best models and hand-tuning their parameters, we are unable to achieve an accuracy of better than 12 dB root mean squared error (RMSE)—four orders of magnitude away from ground truth

    Data from: Depth-to-water mediates bryophyte response to harvesting in boreal forests

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    1. Site moisture is an important component of the forest landscape for maintaining biodiversity, including forest-floor bryophytes, but little is known about its role in shaping understory responses to harvesting. 2. We investigated the influence of site wetness, determined using a remotely-sensed, topographic depth-to-water (DTW) index, on responses of bryophyte cover, richness, diversity, and composition to variable retention harvesting (comparing: 2% [clear-cut], 20%, and 50% dispersed green tree retention and uncut controls [100% retention]) in three boreal forest cover-types (broadleaf, mixed, and conifer forests) in western Canada. The DTW index provides an approximation of depth to water at or below the soil surface, and was derived from wet-areas mapping based on discrete Airborne Laser Scanning data acquired over an experimentally harvested landscape located in northwestern Alberta, Canada. 3. The effectiveness of leaving retention (versus clear-cutting) for conserving bryophyte communities depended on site wetness, as indicated by DTW, with the specifics varying among forest types. In broadleaf forests, bryophyte cover and richness were generally low and not much affected by harvesting but drier sites had higher richness and a few more unique species. In mixed and conifer forests, leaving retention (versus clear-cutting) on wetter (versus drier) sites was more effective for conserving bryophyte cover, wetter sites had higher total species richness, and more species were exclusive to wetter sites. 4. Synthesis and applications. Site wetness, as indicated using the remotely-sensed topographic site wetness index "depth-to-water," mediates bryophyte responses to variable-retention harvests. Specifically, our results suggested that in conifer and mixed forests it would be more beneficial to target wetter sites for retention patches or dispersed retention whereas in broadleaf sites there might be a slight advantage to targeting drier sites. Our study demonstrates that this tool could be used to inform management decisions around leaving dispersed or patch retention.28-Jan-201

    Bryophyte species and depth-to-water index values

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    Bryophyte (mosses and liverworts) species cover data and estimation of depth-to-water index values for retention harvest sites sampled in northwestern Alberta, Canada
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