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Annual Allerton Conference on Communication, Control, and Computing

作者： Yury Polyanskiy Department of Electrical Engineering and Computer Science MIT Cambridge MA USA

It is demonstrated that codewords of good codes for the additive white Gaussian noise (AWGN) channel become more and more isotropically distributed (in the sense of evaluating quadratic forms) and resemble white Gaussian noise (in the sense of ℓ p norms) as the code approaches closer to the fundamental limits. In particular, it is shown that the optimal Gaussian code must necessarily have peak-to-average power ratio (PAPR) of order log n.

关键词： Manganese Zinc Polynomials Peak to average power ratio Dispersion AWGN channels Additive white noise

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Learning k-Modal Distributions via Testing 12

Learning k-Modal Distributions via Testing

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Annual ACM-Society for Industrial and Applied Mathmatics Symposium on Discrete Algorithms

作者： Constantinos Daskalakis Ilias Diakonikolas Rocco A. Servedio Electrical Engineering and Computer Science Department MIT Computer Science Division UC Berkeley Department of Computer Science Columbia University

ISBN: (纸本)9781611972108

A k-modal probability distribution over the domain {1, …, n} is one whose histogram has at most k "peaks" and "valleys." Such distributions are natural generalizations of monotone (k = 0) and unimodal (k = 1) probability distributions, which have been intensively studied in probability theory and statistics. In this paper we consider the problem of learning an unknown k-modal distribution. The learning algorithm is given access to independent samples drawn from the k-modal distribution p, and must output a hypothesis distribution p{top}^ such that with high probability the total variation distance between p and p{top}^ is at most ε. We give an efficient algorithm for this problem that runs in time poly(k, log(n), 1/ε). For k ≤~O((log n)~(1/2)), the number of samples used by our algorithm is very close (within an O(log(1/ε)) factor) to being information-theoretically optimal. Prior to this work computationally efficient algorithms were known only for the cases k = 0， 1 [Bir87b, Bir97]. A novel feature of our approach is that our learning algorithm crucially uses a new property testing algorithm as a key subroutine. The learning algorithm uses the property tester to efficiently decompose the k-modal distribution into k (near)-monotone distributions, which are easier to learn.

关键词： learning algorithms Probability distribution Probability Theory algorithms efficient algorithm Learning

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Optimal placement of uncoded memoryless regenerators for OOK signaling

Optimal placement of uncoded memoryless regenerators for OOK...

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International Conference on Telecommunications (ICT)

作者： Ibrahim Abou-Faycal Muriel Médard Department of Electrical and Computer Engineering American University of Beirut Beirut Lebanon Department of Electrical Engineering and Computer Science MIT Cambridge USA

We study the problem of relay design and placement for On-Off Keying signals. We assume that the relay is memoryless and consider both, coherent and non-coherent devices. We derive the optimal coherent relay and compare its performance and placement to those of a coherent hard-limiter and a non-coherent one. Overall we note that the use of a coherent hard-limiter is near optimal, especially after placement optimization, and its performance degradation is mainly due to the energy-inefficiency of OOK signals.

关键词： Relays Receivers Optimization Noise Performance evaluation Binary phase shift keying Repeaters

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Studies on the Formation and Evolution of Polar Cap Ionization Patches

Studies on the Formation and Evolution of Polar Cap Ionizati...

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第三届全球华人空间/太空天气科学大会

作者： Qing-He Zhang Bei-Chen Zhang Michael Lockwood Jran Moen J.Michael Ruohoniemi Evan G.Thomas Shun-Rong Zhang Rui-Yuan Liu Mark Lester School of Space Science and Physics Shandong University at Weihai SOA Key Laboratory for Polar Science Polar Research Institute of China Department of Meteorology University of Reading Earley Gate P.O. Box 243 RG6 6BB UK Department of Physics University of Oslo Blindern Oslo Norway Bradley Department of Electrical & Computer Engineering Virginia Tech Blacksburg VA USA MIT Haystack Observatory Westford MA 01886 USA Department of physics and Astronomy University of Leicester Leicester UK

Session:空间天气科学前沿-电离层Type of presentation:口头报告Key word:Patches of ionization are common in the polar ionosphere where their motion and associ-ated density gradients give variable disturbances to High Frequency(HF)radio communic-ations,over-the-horizon radar location errors,and disruption and errors to satellite naviga-tion and *** formation and evolution

关键词： Studies on the Formation and Evolution of Polar Cap Ionization Patches

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Results on combinatorial joint source-channel coding

Results on combinatorial joint source-channel coding

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IEEE (first ITW conference of the year) Information Theory Workshop (ITW)

作者： Yuval Kochman Arya Mazumdar Yury Polyanskiy School of Computer Science and Engineering Hebrew University of Jerusalem Jerusalem Israel Department of Electrical Engineering and Computer Science MIT Cambridge MA USA

This paper continues the investigation of the combinatorial formulation of the joint source-channel coding problem. In particular, the connections are drawn to error-reducing codes, isometric embeddings and list-decodable codes. The optimal performance for the repetition construction is derived and is shown to be achievable by low complexity Markov decoders. The compound variation of the problem is proposed and some initial results are put forward.

关键词： Decoding Error correction codes Encoding Markov processes Compounds Conferences

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The adversarial joint source-channel problem

The adversarial joint source-channel problem

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IEEE International Symposium on Information Theory

ISBN: (纸本)9781467325790

This paper introduces the problem of joint source-channel coding in the setup where channel errors are adversarial and the distortion is worst case. Unlike the situation in the case of stochastic source-channel model, the separation principle does not hold in adversarial setup. This surprising observation demonstrates that designing good distortion-correcting codes cannot be done by serially concatenating good covering codes with good error-correcting codes. The problem of the joint code design is addressed and some initial results are offered.

关键词： Decoding Channel coding Error correction codes Joints Stochastic processes Manganese

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Robust Minimum Energy Wireless Routing for Underwater Acoustic Communication Networks

Robust Minimum Energy Wireless Routing for Underwater Acoust...

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Institute of electrical and Electronics Engineers Globecom Workshops

作者： Brooks L. Reed Milica Stojanovic Urbashi mitra Franz S. Hover MIT/WHOI Joint Program in Oceanographic Engineering Northeastern University Department of Electrical Engineering University of Southern California Department of Electrical Engineering and Computer Science MIT Department of Mechanical Engineering

ISBN: (纸本)9781467349420

Marine robots are an increasingly attractive means for observing and monitoring the ocean, but underwater acoustic communications remain a major challenge. The channel exhibits long delay spreads with frequency-dependent attenuation;moreover, it is time-varying. We consider the minimum energy wireless transmission problem [MET], augmented by the practical condition that constraints on link power must be satisfied in probability. For this, we formulate the robust counterpart of the multicommodity mixed-integer linear programming (MDLP) model from Haugland and Yuan [1], and derive scaled power levels that account for uncertainty. Our main result is that the deterministic formulation with these scaled power levels recovers exactly the optimal robust solution in the absence of correlations, and therefore allows for efficient solution via MILP. This approach achieves significant power improvements over heuristics, and naturally lends itself to vehicle networks.

关键词： underwater acoustic communication Energy sources networks(communications) wireless power level Power (Psychology) mobile data link protocol Heuristics Vehicle Network Network routing

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Efficiency-Risk Tradeoffs in Dynamic Oligopoly Markets - with application to electricity markets

Efficiency-Risk Tradeoffs in Dynamic Oligopoly Markets - wit...

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IEEE Annual Conference on Decision and Control

作者： Qingqing Huang Mardavij Roozbehani Munther A. Dahleh LIDS Laboratory for Information and Decision Systems (LIDS) Massachusetts Institute of Technology (MIT) Electrical Engineering and Computer Science (EECS) at MIT

ISBN: (纸本)9781467320658

In this paper, we examine in an abstract framework, how a tradeoff between efficiency and risk arises in different dynamic oligopolistic market architectures. We consider a market in which there is a monopolistic resource provider and agents that enter and exit the market following a random process. Self-interested and fully rational agents dynamically update their resource consumption decisions over a finite time horizon, under the constraint that the total resource consumption requirements are met before each individual's deadline. We then compare the statistics of the stationary aggregate demand processes induced by the non-cooperative and cooperative load scheduling schemes. We show that although the non-cooperative load scheduling scheme leads to an efficiency loss - widely known as the "price of anarchy" - the stationary distribution of the corresponding aggregate demand process has a smaller tail. This tail, which corresponds to rare and undesirable demand spikes, is important in many applications of interest. On the other hand, when the agents can cooperate with each other in optimizing their total cost, a higher market efficiency is achieved at the cost of a higher probability of demand spikes. We thus posit that the origins of endogenous risk in such systems may lie in the market architecture, which is an inherent characteristic of the system.

关键词： power markets tradeoffs Agents load dispatching Stochastic Processes oligopoly Resource utilization origins

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Direct Observations of the Evolution of Polar Cap Ionization Patches

Direct Observations of the Evolution of Polar Cap Ionization...

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中国空间科学学会空间物理学专业委员会第十五届全国日地空间物理学研讨会

作者： Qing-He Zhang Bei-Chen Zhang Michael Lockwood Hong-Qiao Hu Jφran Moen Qing-He Zhang Bei-Chen Zhang Michael Lockwood Hong-Qiao Hu Jφran Moen John M.Ruohoniemi Evan G.Thomas Shun-Rong Zhang Hui-Gen Yang Rui-Yuan Liu Kathryn A.McWilliams Joseph.B.H.Baker SOA Key Laboratory for Polar Science Polar Research Institute of China Department of Meteorology University of ReadingEarley GateP.O.Box 243RG6 6BBUK Department of Physics University of OsloBlindernOsloNorway Bradley Department of Electrical & Computer Engineering Virginia TechBlacksburgVirginiaUSA MIT Haystack Observatory WestfordMA 01886USA Institute of Space and Atmospheric Studies University of SaskatchewanSaskatoonSaskatchewanCanada

Patches of ionization are common in the polar ionosphere where their motion and associated density gradients give variable disturbances to High Frequency(HF)radio communications,over-the-horizon radar location errors,and disruption and errors to satellite navigation and *** formation and evolution are poorly understood,particularly under disturbed space weather *** report direct observations of the full evolution of patches during a geomagnetic storm,including formation,polar cap entry,transpolar evolution,polar cap exit,and sunward return *** observations show that modulation of nightside reconnection in the substorm cycle of the magnetosphere helps form the gaps between patches where steady convection would give a"tongue"of ionization(TOI).

关键词： Direct Observations of the Evolution of Polar Cap Ionization Patches

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Machine learning with operational costs

The Journal of Machine Learning Research

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The Journal of Machine Learning Research 2013年第1期14卷

作者： Kevin Murphy Bernhard Schölkopf Theja Tulabandhula Cynthia Rudin Google MPI for Intelligent Systems Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA MIT Sloan School of Management and Operations Research Center Massachusetts Institute of Technology Cambridge MA

This work proposes a way to align statistical modeling with decision making. We provide a method that propagates the uncertainty in predictive modeling to the uncertainty in operational cost, where operational cost is the amount spent by the practitioner in solving the problem. The method allows us to explore the range of operational costs associated with the set of reasonable statistical models, so as to provide a useful way for practitioners to understand uncertainty. To do this, the operational cost is cast as a regularization term in a learning algorithm's objective function, allowing either an optimistic or pessimistic view of possible costs, depending on the regularization parameter. From another perspective, if we have prior knowledge about the operational cost, for instance that it should be low, this knowledge can help to restrict the hypothesis space, and can help with generalization. We provide a theoretical generalization bound for this scenario. We also show that learning with operational costs is related to robust optimization.

关键词： covering numbers decision theory optimization statistical learning theory

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