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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 con-tents into a finite capacity cache memory of a user equipmentin order to reduce the long-term average energy consumption ina wireless network. We consider an online social network (OSN)framework, in which new contents are generated over time andeach content remains relevant to the user for a random timeperiod, called thelifetimeof the content. The user accesses theOSN through a wireless network at random time instants todownload and consume all the relevant contents. Downloadingcontents has an energy cost that depends on the channel state andthe number of downloaded contents. Our aim is to reduce thelong-term average energy consumption by proactively cachingcontents at favorable channel conditions.In previous work, it was shown that the optimal caching policyis infeasible to compute (even with the complete knowledge of astochastic model describing the system), and a simple family ofthreshold policies was introduced and optimised using the finitedifference method. In this paper we improve upon both com-ponents of this approach: we use linear function approximation(LFA) to better approximate the considered family of cachingpolicies, and apply the REINFORCE algorithm to optimise itsparameters. Numerical simulations show that the new approachprovides reduction in both the average energy cost and therunning time for policy optimisation.

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

    Energy-efficient wireless content delivery with proactive caching

    , 2nd Content Caching and Delivery in Wireless Networks Workshop (CCDWN 2017), Publisher: IEEE

    We propose an intelligent proactive content cachingscheme to reduce the energy consumption in wireless downlink.We consider an online social network (OSN) setting where newcontents are generated over time, and remainrelevantto theuser for a random lifetime. Contents are downloaded to the userequipment (UE) through a time-varying wireless channel at anenergy cost that depends on the channel state and the number ofcontents downloaded. The user accesses the OSN at random timeinstants, and consumes all the relevant contents. To reduce theenergy consumption, we proposeproactive cachingof contentsunder favorable channel conditions to a finite capacity cachememory. Assuming that the channel quality (or equivalently, thecost of downloading data) is memoryless over time slots, we showthat the optimal caching policy, which may replace contents inthe cache with shorter remaining lifetime with contents at theserver that remain relevant longer, has a threshold structurewith respect to the channel quality. Since the optimal policy iscomputationally demanding in practice, we introduce a simplifiedcaching 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 proposedcaching scheme significantly reduces the energy consumptioncompared 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, Pages: 854-864, ISSN: 1524-9050
  • 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

  • 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
    Kokuti A, Gelenbe E, 2014,

    Directional Navigation Improves Opportunistic Communication for Emergencies

    , Sensors, Vol: 14, Pages: 15387-15399, ISSN: 1424-8220

    We present a novel direction based shortest path search algorithm to guideevacuees during an emergency. It uses opportunistic communications (oppcomms) withlow-cost wearable mobile nodes that can exchange packets at close range of a few to sometens of meters without help of an infrastructure. The algorithm seeks the shortest path to exitswhich are safest with regard to a hazard, and is integrated into an autonomous EmergencySupport System (ESS) to guide evacuees in a built environment. The algorithm proposedthat ESSs are evaluated with the DBES (Distributed Building Evacuation Simulator) bysimulating a shopping centre where fire is spreading. The results show that the directionalpath finding algorithm can offer significant improvements for the evacuees.

  • Journal article
    Gelenbe E, 2014,

    Emergency Navigation without an Infrastructure

    , Sensors, Vol: 14, Pages: 15142-15162, ISSN: 1424-8220
  • Journal article
    Gelenbe E, Abdelrahman OH, 2014,

    Search in the Universe of Big Networks and Data

    , IEEE Network, Vol: 28, Pages: 20-25, ISSN: 0890-8044

    Searching in the Internet for some object characterisedby its attributes in the form of data, such as a hotel ina certain city whose price is less than something, is one of ourmost common activities when we access the Web. We discuss thisproblem in a general setting, and compute the average amount oftime and the energy it takes to find an object in an infinitely largesearch space. We consider the use of N search agents which actconcurrently. Both the case where the search agent knows whichway it needs to go to find the object, and the case where thesearch agent is perfectly ignorant and may even head away fromthe object being sought. We show that under mild conditionsregarding the randomness of the search and the use of a time-out,the search agent will always find the object despite the fact thatthe search space is infinite. We obtain a formula for the averagesearch time and the average energy expended by N search agentsacting concurrently and independently of each other. We see thatthe time-out itself can be used to minimise the search time andthe amount of energy that is consumed to find an object. Anapproximate formula is derived for the number of search agentsthat can help us guarantee that an object is found in a giventime, and we discuss how the competition between search agentsand other agents that try to hide the data object, can be usedby opposing parties to guarantee their own success.

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

    Structural Generative Descriptions for Time Series Classification

  • 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
    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
  • Journal article
    Kim H, Park T, Gelenbe E, 2014,

    Identifying disease candidate genes via large-scale gene network analysis

  • Conference paper
    Gelenbe E, Han Q, 2014,

    Near-Optimal Emergency Evacuation with Rescuer Allocation

    , 12th IEEE International Conference on Pervasive Computing and Communication (PERCOM), Publisher: IEEE, Pages: 314-319, ISSN: 2474-2503
  • Conference paper
    Bi H, Gelenbe E, 2014,

    Routing Diverse Evacuees with Cognitive Packets

    , 12th IEEE International Conference on Pervasive Computing and Communication (PERCOM), Publisher: IEEE, Pages: 291-296, ISSN: 2474-2503
  • Conference paper
    Desmet A, Gelenbe E, 2014,

    Capacity Based Evacuation with Dynamic Exit Signs

    , 12th IEEE International Conference on Pervasive Computing and Communication (PERCOM), Publisher: IEEE, Pages: 332-337, ISSN: 2474-2503
  • Journal article
    Yu C-M, Ni G-K, Chen I-Y, Gelenbe E, Kuo S-Yet al., 2014,

    Top-k Query Result Completeness Verification in Tiered Sensor Networks


    Storage nodes are expected to be placed as an intermediate tier of large scale sensor networks for caching the collected sensor readings and responding to queries with benefits of power and storage saving for ordinary sensors. Nevertheless, an important issue is that the compromised storage node may not only cause the privacy problem, but also return fake/incomplete query results. We propose a simple yet effective dummy reading-based anonymization framework, under which the query result integrity can be guaranteed by our proposed verifiable top- k query (VQ) schemes. Compared with existing works, the VQ schemes have a fundamentally different design philosophy and achieve the lower communication complexity at the cost of slight detection capability degradation. Analytical studies, numerical simulations, and prototype implementations are conducted to demonstrate the practicality of our proposed methods.

  • 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
    Pei Y, Kim T-K, Zha H, 2013,

    Unsupervised Random Forest Manifold Alignment for Lipreading

    , IEEE Int. Conf. on Computer Vision (ICCV)
  • Journal article
    Filippoupolitis A, Gorbil G, Gelenbe E, 2013,

    Spatial Computers for Emergency Support

    , COMPUTER JOURNAL, Vol: 56, Pages: 1399-1416, ISSN: 0010-4620
  • 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)
  • 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
    Abdelrahman OH, Gelenbe E, Goerbil G, Oklander Bet al., 2013,

    Mobile network anomaly detection and mitigation: The NEMESYS approach

    , 28th International Symposium on Computer and Information Sciences (ISCIS), Publisher: Springer, Pages: 429-438, ISSN: 1876-1100

    Mobile malware and mobile network attacks are becoming a significant threat that accompanies the increasing popularity of smart phones and tablets. Thus in this paper we present our research vision that aims to develop a network-based security solution combining analytical modelling, simulation and learning, together with billing and control-plane data, to detect anomalies and attacks, and eliminate or mitigate their effects, as part of the EU FP7 NEMESYS project. These ideas are supplemented with a careful review of the state-of-the-art regarding anomaly detection techniques that mobile network operators may use to protect their infrastructure and secure users against malware.

  • Conference paper
    Gelenbe E, Goerbil G, Tzovaras D, Liebergeld S, Garcia D, Baltatu M, Lyberopoulos Get al., 2013,

    NEMESYS: Enhanced network security for seamless service provisioning in the smart mobile ecosystem

    , 28th International Symposium on Computer and Information Sciences (ISCIS), Publisher: Springer, Pages: 369-378, ISSN: 1876-1100

    As a consequence of the growing popularity of smart mobile devices, mobile malware is clearly on the rise, with attackers targeting valuable user information and exploiting vulnerabilities of the mobile ecosystems. With the emergence of large-scale mobile botnets, smartphones can also be used to launch attacks on mobile networks. The NEMESYS project will develop novel security technologies for seamless service provisioning in the smart mobile ecosystem, and improve mobile network security through better understanding of the threat landscape. NEMESYS will gather and analyze information about the nature of cyber-attacks targeting mobile users and the mobile network so that appropriate counter-measures can be taken. We will develop a data collection infrastructure that incorporates virtualized mobile honeypots and a honeyclient, to gather, detect and provide early warning of mobile attacks and better understand the modus operandi of cyber-criminals that target mobile devices. By correlating the extracted information with the known patterns of attacks from wireline networks, we will reveal and identify trends in the way that cyber-criminals launch attacks against mobile devices.

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

    Generic Object Crowd Tracking by Multi-Task Learning

    , British Machine Vision Conference (BMVC)

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