Environmental Imaginaries: Climate Change as an Object of Urban Governance

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Lightweight Security for Network Coding

Under the emerging network coding paradigm, intermediate nodes in the network are allowed not only to store and forward packets but also to process and mix different data flows. We propose a low-complexity cryptographic scheme that exploits the inherent security provided by random linear network coding and offers the advantage of reduced overhead in comparison to traditional end-to-end encryption of the entire data. Confidentiality is achieved by protecting (or "locking") the source coefficients required to decode the encoded data, without preventing intermediate nodes from running their standard network coding operations. Our scheme can be easily combined with existing techniques that counter active attacks.Comment: Proc. of the IEEE International Conference on Communications (ICC 2008), Beijing, China, May 200

Health outcomes of a subsidised fruit and vegetable program for Aboriginal children in northern New South Wales

Objective: To evaluate the impact of a fruit and vegetable subsidy program on short-term health outcomes of disadvantaged Aboriginal children.Design, setting and participants: A before-and-after study involving clinical assessments, health record audits and blood testing of all children aged 0–17 years (n = 167) from 55 participating families at baseline and after 12 months at three Aboriginal community-controlled health services in New South Wales. All assessments were completed between December 2008 and September 2010.Intervention: A weekly box of subsidised fruit and vegetables linked to preventive health services and nutrition promotion at an Aboriginal Medical Service.Main outcome measures: Change in episodes of illness, health service and emergency department attendances, antibiotic prescriptions and anthropometry.Results: There was a significant decrease in oral antibiotics prescribed (− 0.5 prescriptions/year; 95% CI, − 0.8 to − 0.2) during 12 months of participation in the program compared with the 12 months before the program. The proportion of children classified as overweight or obese at baseline was 28.3% (38/134) and the proportion in each weight category did not change (P = 0.721) after 12 months. A small but significant increase in mean haemoglobin level (3.1 g/L; 95% CI, 1.4–4.8 g/L) was shown, although the proportion with iron deficiency (baseline, 41%; follow-up, 37%; P = 0.440) and anaemia (baseline, 8%; follow-up, 5%; P = 0.453) did not change significantly.Conclusion: This fruit and vegetable subsidy program was associated with improvements in some indicators of short-term health status among disadvantaged Aboriginal children. A controlled trial is warranted to investigate the sustainability and feasibility of healthy food subsidy programs in Australia

Asynchronous CDMA Systems with Random Spreading-Part II: Design Criteria

Totally asynchronous code-division multiple-access (CDMA) systems are addressed. In Part I, the fundamental limits of asynchronous CDMA systems are analyzed in terms of spectral efficiency and SINR at the output of the optimum linear detector. The focus of Part II is the design of low-complexity implementations of linear multiuser detectors in systems with many users that admit a multistage representation, e.g. reduced rank multistage Wiener filters, polynomial expansion detectors, weighted linear parallel interference cancellers. The effects of excess bandwidth, chip-pulse shaping, and time delay distribution on CDMA with suboptimum linear receiver structures are investigated. Recursive expressions for universal weight design are given. The performance in terms of SINR is derived in the large-system limit and the performance improvement over synchronous systems is quantified. The considerations distinguish between two ways of forming discrete-time statistics: chip-matched filtering and oversampling

Asynchronous CDMA Systems with Random Spreading-Part I: Fundamental Limits

Spectral efficiency for asynchronous code division multiple access (CDMA) with random spreading is calculated in the large system limit allowing for arbitrary chip waveforms and frequency-flat fading. Signal to interference and noise ratios (SINRs) for suboptimal receivers, such as the linear minimum mean square error (MMSE) detectors, are derived. The approach is general and optionally allows even for statistics obtained by under-sampling the received signal. All performance measures are given as a function of the chip waveform and the delay distribution of the users in the large system limit. It turns out that synchronizing users on a chip level impairs performance for all chip waveforms with bandwidth greater than the Nyquist bandwidth, e.g., positive roll-off factors. For example, with the pulse shaping demanded in the UMTS standard, user synchronization reduces spectral efficiency up to 12% at 10 dB normalized signal-to-noise ratio. The benefits of asynchronism stem from the finding that the excess bandwidth of chip waveforms actually spans additional dimensions in signal space, if the users are de-synchronized on the chip-level. The analysis of linear MMSE detectors shows that the limiting interference effects can be decoupled both in the user domain and in the frequency domain such that the concept of the effective interference spectral density arises. This generalizes and refines Tse and Hanly's concept of effective interference. In Part II, the analysis is extended to any linear detector that admits a representation as multistage detector and guidelines for the design of low complexity multistage detectors with universal weights are provided

Expanded Multiband Super-Nyquist CAP Modulation for Highly Bandlimited Organic Visible Light Communications

In this article, we experimentally demonstrate a novel expanded nonorthogonal multiband super-Nyquist carrier-less amplitude and phase (m-ESCAP) modulation for bandlimited organic visible light communication (VLC) systems. The proposed scheme has the same bandwidth requirement as the conventional m-CAP while breaking the orthogonality between subcarriers by purposely overlapping them. We compare m-ESCAP with the conventional m-CAP and a compressed nonorthogonal version of m-CAP (m-SCAP) in terms of measured bit error rate (BER) performance, bit rates, and spectral efficiencies. We show that the m-ESCAP system offers improvement in the bit rate of $\sim$ 10% and 20% compared to the m-CAP and m-SCAP, respectively, and in the spectral efficiency of $\sim$ 20% compared to m-CAP. These gains are achieved at the cost of increased BER, which, however, remains below the 7% forward error correction limit