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  • Conference paper
    Ceran ET, Gunduz D, Gyorgy A, 2018,

    Average age of information with hybrid ARQ under a resource constraint

    , Wireless Communications and Networking Conference (WCNC), Publisher: IEEE, ISSN: 1525-3511

    Scheduling the transmission of status updates over an error-prone communication channel is studied in order to minimize the long-term average age of information (AoI) at the destination under a constraint on the average number of transmissions at the source node. After each transmission, the source receives an instantaneous ACK/NACK feedback, and decides on the next update without prior knowledge on the success of future transmissions. First, the optimal scheduling policy is studied under different feedback mechanisms when the channel statistics are known; in particular, the standard automatic repeat request (ARQ) and hybrid ARQ (HARQ) protocols are considered. Then, for an unknown environment, an average-cost reinforcement learning (RL) algorithm is proposed that learns the system parameters and the transmission policy in real time. The effectiveness of the proposed methods are verified through numerical simulations.

  • Conference paper
    Somuyiwa S, Gyorgy A, Gunduz D, 2017,

    Improved policy representation and policy search for proactive content caching in wireless networks

    , 15th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, Publisher: IEEE

    We study the problem of proactively pushing contents into a finite capacity cache memory of a user equipment in order to reduce the long-term average energy consumption in a wireless network. We consider an online social network (OSN) framework, in which new contents are generated over time and each content remains relevant to the user for a random time period, called the lifetime of the content. The user accesses the OSN through a wireless network at random time instants to download and consume all the relevant contents. Downloading contents has an energy cost that depends on the channel state and the number of downloaded contents. Our aim is to reduce the long-term average energy consumption by proactively caching contents at favorable channel conditions. In previous work, it was shown that the optimal caching policy is infeasible to compute (even with the complete knowledge of a stochastic model describing the system), and a simple family of threshold policies was introduced and optimised using the finite difference method. In this paper we improve upon both components of this approach: we use linear function approximation (LFA) to better approximate the considered family of caching policies, and apply the REINFORCE algorithm to optimise its parameters. Numerical simulations show that the new approach provides reduction in both the average energy cost and the running time for policy optimisation.

  • Conference paper
    Somuyiwa S, Gyorgy A, Gunduz D, 2017,

    Energy-efficient wireless content delivery with proactive caching

    , 15th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt), Publisher: IEEE

    We propose an intelligent proactive content caching scheme to reduce the energy consumption in wireless downlink. We consider an online social network (OSN) setting where new contents are generated over time, and remain relevant to the user for a random lifetime. Contents are downloaded to the user equipment (UE) through a time-varying wireless channel at an energy cost that depends on the channel state and the number of contents downloaded. The user accesses the OSN at random time instants, and consumes all the relevant contents. To reduce the energy consumption, we propose proactive caching of contents under favorable channel conditions to a finite capacity cache memory. Assuming that the channel quality (or equivalently, the cost of downloading data) is memoryless over time slots, we show that the optimal caching policy, which may replace contents in the cache with shorter remaining lifetime with contents at the server that remain relevant longer, has a threshold structure with respect to the channel quality. Since the optimal policy is computationally demanding in practice, we introduce a simplified caching scheme and optimize its parameters using policy search. We also present two lower bounds on the energy consumption. We demonstrate through numerical simulations that the proposed caching scheme significantly reduces the energy consumption compared to traditional reactive caching tools, and achieves close- to-optimal performance for a wide variety of system parameters.

  • Journal article
    Pitt J, Busquets D, Riveret R, 2015,

    The pursuit of computational justice in open systems

    , AI & SOCIETY, Vol: 30, Pages: 359-378, ISSN: 0951-5666
  • Journal article
    Thajchayapong S, Barria JA, 2015,

    Spatial inference of traffic transition using micro-macro traffic variables

    , IEEE Transactions on Intelligent Transportation Systems, Vol: 16, Pages: 854-864, ISSN: 1524-9050

    This paper proposes an online traffic inference algorithm for road segments in which local traffic information cannot be directly observed. Using macro-micro traffic variables as inputs, the algorithm consists of three main operations. First, it uses interarrival time (time headway) statistics from upstream and downstream locations to spatially infer traffic transitions at an unsupervised piece of segment. Second, it estimates lane-level flow and occupancy at the same unsupervised target site. Third, it estimates individual lane-level shockwave propagation times on the segment. Using real-world closed-circuit television data, it is shown that the proposed algorithm outperforms previously proposed methods in the literature.

  • Journal article
    Blasco P, Gunduz D, 2015,

    Multi-Access Communications With Energy Harvesting: A Multi-Armed Bandit Model and the Optimality of the Myopic Policy

    , IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, Vol: 33, Pages: 585-597, ISSN: 0733-8716
  • Journal article
    Gomez-Vilardebo J, Gunduz D, 2015,

    Smart Meter Privacy for Multiple Users in the Presence of an Alternative Energy Source

    , IEEE Transactions on Information Forensics and Security, Vol: 10, Pages: 132-141, ISSN: 1556-6021
  • Journal article
    Orhan O, Gunduz D, Erkip E, 2014,

    Energy Harvesting Broadband Communication Systems With Processing Energy Cost

    , IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, Vol: 13, Pages: 6095-6107, ISSN: 1536-1276
  • Journal article
    Pitt J, Busquets D, Macbeth S, 2014,

    Distributive justice for self-organised common-pool resource management

    , ACM Transactions on Autonomous and Adaptive Systems, Vol: 9, Pages: 1-24, ISSN: 1556-4665

    In this article, we complement Elinor Ostrom’s institutional design principles for enduring common-pool resource management with Nicholas Rescher’s theory of distributive justice based on the canon of legitimate claims. Two of Ostrom’s principles are that the resource allocation method should be congruent with the local environment, and that those affected by the allocation method (the appropriators) should participate in its selection. However, these principles do not say anything explicitly about the fairness of the allocation method or the outcomes it produces: for this, we need a mechanism for distributive justice. Rescher identified a number of different mechanisms, each of which had both its merits and demerits, and instead maintained that distributive justice consisted in identifying the legitimate claims in context, accommodating multiple claims in case of plurality, and reconciling them in case of conflict. Accordingly, we specify a logical axiomatisation of the principles with the canon of legitimate claims, whereby a set of claims is each represented as a voting function, which collectively determine the rank order in which resources are allocated. The appropriators vote on the weight attached to the scoring functions, and so self-organise the allocation method, taking into account both the plurality of and conflict between the claims. Therefore, the appropriators exercise collective choice over the method, and the method itself is congruent with the local environment, taking into account both the resources available and the relative claims of the appropriators. Experiments with a variant of the linear public good game show that this pluralistic self-organising approach produces a better balance of utility and fairness (for agents that comply with the rules of the game) compared to monistic or fixed approaches, provide “fairness over time” (a series of ostensibly unfair individual allocations is revealed to be cumulatively fa

  • Journal article
    Garcia-Trevino ED, Barria JA, 2014,

    Structural generative descriptions for time series classification

    , IEEE Transactions on Cybernetics, Vol: 44, Pages: 1978-1991, ISSN: 1083-4419

    In this paper, we formulate a novel time series representation framework that captures the inherent data dependency of time series and that can be easily incorporated into existing statistical classification algorithms. The impact of the proposed data representation stage in the solution to the generic underlying problem of time series classification is investigated. The proposed framework, which we call structural generative descriptions moves the structural time series representation to the probability domain, and hence is able to combine statistical and structural pattern recognition paradigms in a novel fashion. Two algorithm instantiations based on the proposed framework are developed. The algorithms are tested and compared using different publicly available real-world benchmark data. Results reported in this paper show the potential of the proposed representation framework, which in the experiments investigated, performs better or comparable to state-of-the-art time series description techniques.

  • Journal article
    Murin Y, Dabora R, Gunduz D, 2014,

    On Joint Source-Channel Coding for Correlated Sources Over Multiple-Access Relay Channels

    , IEEE TRANSACTIONS ON INFORMATION THEORY, Vol: 60, Pages: 6231-6253, ISSN: 0018-9448
  • Journal article
    Tuncel E, Gunduz D, 2014,

    Identification and Lossy Reconstruction in Noisy Databases

    , IEEE TRANSACTIONS ON INFORMATION THEORY, Vol: 60, Pages: 822-831, ISSN: 0018-9448
  • Conference paper
    Deniz O, Serrano I, Bueno G, Kim T-Ket al., 2014,

    Fast Violence Detection in Video

    , The 9th International Conference on Computer Vision Theory and Applications (VISAPP)
  • Journal article
    Gunduz D, Stamatiou K, Michelusi N, Zorzi Met al., 2014,

    Designing Intelligent Energy Harvesting Communication Systems

    , IEEE COMMUNICATIONS MAGAZINE, Vol: 52, Pages: 210-216, ISSN: 0163-6804
  • Conference paper
    Petruzzi PE, Busquets D, Pitt J, 2014,

    Experiments with Social Capital in Multi-agent Systems

    , 17th International Conference on Principles and Practice of Multi-Agent Systems (PRIMA), Publisher: SPRINGER-VERLAG BERLIN, Pages: 18-33, ISSN: 0302-9743
  • Conference paper
    Tang D, Yu T, Kim T-K, 2013,

    Real-time Articulated Hand Pose Estimation using Semi-supervised Transductive Regression Forests

    , IEEE Int. Conf. on Computer Vision (ICCV)
  • Conference paper
    Pei Y, Kim T-K, Zha H, 2013,

    Unsupervised Random Forest Manifold Alignment for Lipreading

    , IEEE Int. Conf. on Computer Vision (ICCV)
  • Journal article
    Lee K, Su Y, Kim T-K, Demiris Yet al., 2013,

    A syntactic approach to robot imitation learning using probabilistic activity grammars

    , Robotics and Autonomous Systems, Vol: 61, Pages: 1323-1334, ISSN: 0921-8890

    This paper describes a syntactic approach to imitation learning that captures important task structures in the form of probabilistic activity grammars from a reasonably small number of samples under noisy conditions. We show that these learned grammars can be recursively applied to help recognize unforeseen, more complicated tasks that share underlying structures. The grammars enforce an observation to be consistent with the previously observed behaviors which can correct unexpected, out-of-context actions due to errors of the observer and/or demonstrator. To achieve this goal, our method (1) actively searches for frequently occurring action symbols that are subsets of input samples to uncover the hierarchical structure of the demonstration, and (2) considers the uncertainties of input symbols due to imperfect low-level detectors.We evaluate the proposed method using both synthetic data and two sets of real-world humanoid robot experiments. In our Towers of Hanoi experiment, the robot learns the important constraints of the puzzle after observing demonstrators solving it. In our Dance Imitation experiment, the robot learns 3 types of dances from human demonstrations. The results suggest that under reasonable amount of noise, our method is capable of capturing the reusable task structures and generalizing them to cope with recursions.

  • Conference paper
    Luo W, Kim T-K, 2013,

    Generic Object Crowd Tracking by Multi-Task Learning

    , British Machine Vision Conference (BMVC)
  • Journal article
    Tan O, Gunduz D, Poor HV, 2013,

    Increasing Smart Meter Privacy Through Energy Harvesting and Storage Devices

    , IEEE Journal on Selected Areas in Communications, Vol: 31, Pages: 1331-1341, ISSN: 1558-0008

    Smart meters are key elements for the operation of smart grids. By providing near realtime information on the energy consumption of individual users, smart meters increase the efficiency in generation, distribution and storage of energy in a smart grid. The ability of the utility provider to track users' energy consumption inevitably leads to important threats to privacy. In this paper, privacy in a smart metering system is studied from an information theoretic perspective in the presence of energy harvesting and storage units. It is shown that energy harvesting provides increased privacy by diversifying the energy source, while a storage device can be used to increase both the energy efficiency and the privacy of the user. For given input load and energy harvesting rates, it is shown that there exists a trade-off between the information leakage rate, which is used to measure the privacy of the user, and the wasted energy rate, which is a measure of the energy-efficiency. The impact of the energy harvesting rate and the size of the storage device on this trade-off is also studied.

  • Conference paper
    Yu T, Kim T-K, Cipolla R, 2013,

    Unconstrained Monocular 3D Human Pose Estimation by Action Detection and Cross-modality Regression Forest

    , IEEE Conf. on Computer Vision and Pattern Recognition (CVPR)
  • Conference paper
    Gunduz D, Gomez-Vilardebo J, 2013,

    Smart meter privacy in the presence of an alternative energy source

    , IEEE Int'l Conf. on Communications (ICC)
  • Conference paper
    Orhan O, Gunduz D, Erkip E, 2013,

    Optimal packet scheduling for an energy harvesting transmitter with processing cost

    , IEEE Int'l Conf. on Communications (ICC)
  • Conference paper
    Cocco G, Gunduz D, Ibars G, 2013,

    Throughput and delay analysis in video streaming over block-fading channels

    , IEEE Int'l Conf. on Communications (ICC)
  • Journal article
    Blasco P, Gunduz D, Dohler M, 2013,

    A Learning Theoretic Approach to Energy Harvesting Communication System Optimization

    , IEEE Transactions on Wireless Communications, Vol: 12, Pages: 1872-1882, ISSN: 1536-1276

    A point-to-point wireless communication system in which the transmitter isequipped with an energy harvesting device and a rechargeable battery, isstudied. Both the energy and the data arrivals at the transmitter are modeledas Markov processes. Delay-limited communication is considered assuming thatthe underlying channel is block fading with memory, and the instantaneouschannel state information is available at both the transmitter and thereceiver. The expected total transmitted data during the transmitter'sactivation time is maximized under three different sets of assumptionsregarding the information available at the transmitter about the underlyingstochastic processes. A learning theoretic approach is introduced, which doesnot assume any a priori information on the Markov processes governing thecommunication system. In addition, online and offline optimization problems arestudied for the same setting. Full statistical knowledge and causal informationon the realizations of the underlying stochastic processes are assumed in theonline optimization problem, while the offline optimization problem assumesnon-causal knowledge of the realizations in advance. Comparing the optimalsolutions in all three frameworks, the performance loss due to the lack of thetransmitter's information regarding the behaviors of the underlying Markovprocesses is quantified.

  • Journal article
    Bofill M, Busquets D, Munoz V, Villaret Met al., 2013,

    Reformulation based MaxSAT robustness

    , CONSTRAINTS, Vol: 18, Pages: 202-235, ISSN: 1383-7133
  • Journal article
    Guenduez D, Erkip E, Goldsmith A, Poor HVet al., 2013,

    Reliable Joint Source-Channel Cooperative Transmission Over Relay Networks

    , IEEE TRANSACTIONS ON INFORMATION THEORY, Vol: 59, Pages: 2442-2458, ISSN: 0018-9448
  • Conference paper
    Gunduz D, Gomez-Vilardebo J, Tan O, Poor Vet al., 2013,

    Information theoretic privacy for smart meters

    , Information Theory and Applications Workshop (ITA)
  • Journal article
    Kim J, Barria JA, Chang M, Leung VCMet al., 2013,

    Special Issue on Embedded Systems for Interactive Multimedia Services (ES-IMS)

    , ACM TRANSACTIONS ON EMBEDDED COMPUTING SYSTEMS, Vol: 12, ISSN: 1539-9087
  • Journal article
    Guenduez D, Yener A, Goldsmith A, Poor HVet al., 2013,

    The Multiway Relay Channel

    , IEEE TRANSACTIONS ON INFORMATION THEORY, Vol: 59, Pages: 51-63, ISSN: 0018-9448

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