Distortion Minimization in Gaussian Layered Broadcast Coding with Successive Refinement

A transmitter without channel state information (CSI) wishes to send a delay-limited Gaussian source over a slowly fading channel. The source is coded in superimposed layers, with each layer successively refining the description in the previous one. The receiver decodes the layers that are supported by the channel realization and reconstructs the source up to a distortion. The expected distortion is minimized by optimally allocating the transmit power among the source layers. For two source layers, the allocation is optimal when power is first assigned to the higher layer up to a power ceiling that depends only on the channel fading distribution; all remaining power, if any, is allocated to the lower layer. For convex distortion cost functions with convex constraints, the minimization is formulated as a convex optimization problem. In the limit of a continuum of infinite layers, the minimum expected distortion is given by the solution to a set of linear differential equations in terms of the density of the fading distribution. As the bandwidth ratio b (channel uses per source symbol) tends to zero, the power distribution that minimizes expected distortion converges to the one that maximizes expected capacity. While expected distortion can be improved by acquiring CSI at the transmitter (CSIT) or by increasing diversity from the realization of independent fading paths, at high SNR the performance benefit from diversity exceeds that from CSIT, especially when b is large.Comment: Accepted for publication in IEEE Transactions on Information Theor

Global Economic Sustainability Indicator: Analysis and Policy Options for the Copenhagen Process

Summary: The traditional discussion about CO2 emissions and greenhouse gases as a source of global warming has been rather static, namely in the sense that innovation dynamics have not been considered much. Given the global nature of the climate problem, it is natural to develop a more dynamic Schumpeterian perspective and to emphasize a broader international analysis, which takes innovation dynamics and green international competitiveness into account: We discuss key issues of developing a consistent global sustainability indicator, which should cover the crucial dimensions of sustainability in a simple and straightforward way. The basic elements presented here concern genuine savings rates – covering not only depreciations on capital, but on the natural capital as well -, the international competitiveness of the respective country in the field of environmental ("green") goods and the share of renewable energy generation. International benchmarking can thus be encouraged and opportunities emphasized - an approach developed here. This new EIIW-vita Global Sustainability Indicator is consistent with the recent OECD requirements on composite indicators and thus, we suggest new options for policymakers. The US and Indonesia have suffered from a decline in their performance in the period 2000-07; Germany has improved its performance as judged by the new composite indicator whose weights are determined from factor analysis. The countries covered stand for roughly 91% of world GDP, 94% of global exports, 82% of global CO2 emissions and 68% of the population.CO2 Emission, Global worming, Sustainability, International country competitiveness

Outage Capacity of Incremental Relaying at Low Signal-to-Noise Ratios

We present the \epsilon-outage capacity of incremental relaying at low signal-to-noise ratios (SNR) in a wireless cooperative network with slow Rayleigh fading channels. The relay performs decode-and-forward and repetition coding is employed in the network, which is optimal in the low SNR regime. We derive an expression on the optimal relay location that maximizes the \epsilon-outage capacity. It is shown that this location is independent of the outage probability and SNR but only depends on the channel conditions represented by a path-loss factor. We compare our results to the \epsilon-outage capacity of the cut-set bound and demonstrate that the ratio between the \epsilon-outage capacity of incremental relaying and the cut-set bound lies within 1/\sqrt{2} and 1. Furthermore, we derive lower bounds on the \epsilon-outage capacity for the case of K relays.Comment: 5 pages, 4 figures, to be presented at VTC Fall 2009 in Anchorage, Alask

Minimum Expected Distortion in Gaussian Layered Broadcast Coding with Successive Refinement

A transmitter without channel state information (CSI) wishes to send a delay-limited Gaussian source over a slowly fading channel. The source is coded in superimposed layers, with each layer successively refining the description in the previous one. The receiver decodes the layers that are supported by the channel realization and reconstructs the source up to a distortion. In the limit of a continuum of infinite layers, the optimal power distribution that minimizes the expected distortion is given by the solution to a set of linear differential equations in terms of the density of the fading distribution. In the optimal power distribution, as SNR increases, the allocation over the higher layers remains unchanged; rather the extra power is allocated towards the lower layers. On the other hand, as the bandwidth ratio b (channel uses per source symbol) tends to zero, the power distribution that minimizes expected distortion converges to the power distribution that maximizes expected capacity. While expected distortion can be improved by acquiring CSI at the transmitter (CSIT) or by increasing diversity from the realization of independent fading paths, at high SNR the performance benefit from diversity exceeds that from CSIT, especially when b is large.Comment: To appear in the proceedings of the 2007 IEEE International Symposium on Information Theory, Nice, France, June 24-29, 200

Fast Fight Detection

Action recognition has become a hot topic within computer vision. However, the action recognition community has focused mainly on relatively simple actions like clapping, walking, jogging, etc. The detection of specific events with direct practical use such as fights or in general aggressive behavior has been comparatively less studied. Such capability may be extremely useful in some video surveillance scenarios like prisons, psychiatric centers or even embedded in camera phones. As a consequence, there is growing interest in developing violence detection algorithms. Recent work considered the well-known Bag-of-Words framework for the specific problem of fight detection. Under this framework, spatio-temporal features are extracted from the video sequences and used for classification. Despite encouraging results in which high accuracy rates were achieved, the computational cost of extracting such features is prohibitive for practical applications. This work proposes a novel method to detect violence sequences. Features extracted from motion blobs are used to discriminate fight and non-fight sequences. Although the method is outperformed in accuracy by state of the art, it has a significantly faster computation time thus making it amenable for real-time applications

Optical control of magnetization in a room-temperature magnet: V-Cr Prussian blue analog

Journal ArticleWe report reversible photoinduced magnetic phenomena for a V-Cr Prussian blue analog (Tc~350 K). This molecule-based magnet exhibits a decrease in magnetization upon illumination with UV light (λ~350 nm) and reaches a metastable state that has a long lifetime at low temperatures (>106 s at 10 K). This photoexcited magnetic state totally recovers back to the ground state by warming above 250 K, and partially recovers with green light (λ~514 nm) illumination. The effect of green light is triggered only when the sample is previously UV irradiated, suggesting a hidden metastable magnetic state. The photoinduced magnetic effects are proposed to originate from structural distortion that alters the magnetic exchange coupling and/or anisotropy

A Note on the Efficiency Effects of Agglomeration Economies: Turkish Evidence

By using a very novel dataset from Turkish SMEs, this paper investigates the effects of agglomeration economies on productive and allocative efficiency. After controlling for unobserved heterogeneity at the time level, our empirical results from ordered panel probit models provide evidence that clusters have no statistically significant effect on productive efficiency but a negative effect on allocative efficiency. We also show that the increase in prices is not due to increased product differentiation; therefore, it is most likely due to collusion