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  • 1.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    He, Qing
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Minimum-Time Link Scheduling for Emptying Wireless Systems: Solution Characterization and Algorithmic Framework2014In: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 60, no 2, p. 1083-1100Article in journal (Refereed)
    Abstract [en]

    We consider a set of transmitter-receiver pairs, or links, that share a wireless medium and address the problem of emptying backlogged queues with given initial size at the transmitters in minimum time. The problem amounts to determining activation subsets of links, and their time durations, to form a minimum-time schedule. Scheduling in wireless networks has been studied under various formulations before. In this paper, we present fundamental insights and solution characterizations that include: 1) showing that the complexity of the problem remains high for any continuous and increasing rate function; 2) formulating and proving sufficient and necessary optimality conditions of two baseline scheduling strategies that correspond to emptying the queues using one-at-a-time or all-at-once strategies; and 3) presenting and proving the tractability of the special case in which the transmission rates are functions only of the cardinality of the link activation sets. These results are independent of physical-layer system specifications and are valid for any form of rate function. We then develop an algorithmic framework for the solution to this problem. The framework encompasses exact as well as sub-optimal, but fast, scheduling algorithms, all under a unified principle design. Through computational experiments, we finally investigate the performance of several specific algorithms from this framework.

  • 2.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    He, Qing
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    On Emptying a Wireless Network in Minimum Time2012In: 2012 IEEE International Symposium on Information Theory Proceedings (ISIT), Piscataway, NJ, USA: IEEE , 2012, p. 2671-2675Conference paper (Refereed)
    Abstract [en]

    We consider N transmitter-receiver pairs that share a wireless channel and we address the problem of obtaining a schedule for activating subsets of these links so as to empty the transmitter queues in minimum time. Our aim is to provide theoretical insights for the optimality characterization of the problem, using both a cross-layer model formulation, which takes into account the effect of interference on achievable transmission rates, as well as a collision-based model, which does not incorporate the physical layer realities into the problem. We present the basic linear programming formulation of the problem and establish that the optimal schedule need not consist of more than N subset activation frames. We then prove that the problem is NP-hard for all reasonable continuous rate functions. Finally, we obtain sufficient and/or necessary conditions for optimality in a number of special cases.

  • 3.
    He, Qing
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    A Comprehensive Analysis of Optimal Link Scheduling for Emptying a Wireless Network2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wireless communications have become an important part of modern life. The ubiquitous wireless networks and connectivities generate exponentially increasing data traffic. In view of this, wireless network optimization, which aims at utilizing the limited resource, especially spectrum and energy, as efficiently as possible from a network perspective, is essential for performance improvement and sustainable development of wireless communications.

    In the dissertation, we focus on a fundamental problem of wireless network optimization, link scheduling, as well as its subproblem, link activation. The problem type arises because of the nature of wireless media and hence it is of relevance to a wide range of networks with multiple access. We freshen these classic problems up by novel extensions incorporating new technologies of interference management or with new performance metrics. We also revisit the problems in their classic setup to gain new theoretical results and insights for problem-solving. Throughout the study, we consider the problems with a general setup, such that the insights presented in this dissertation are not constrained to a specific technology or network type. Since link activation and scheduling are key elements of access coordination in wireless communications, the study opens up new approaches that significantly improve network performance, and eventually benefit practical applications.

    The dissertation consists of five research papers. The first paper addresses maximum link activation with cooperative transmission and interference cancellation. Papers II and III investigate the minimum-time link scheduling problem in general and a particular class of networks, respectively. In Paper IV, we consider the scheduling problem of emptying a network in its broad form and provide a general optimality condition. In Paper V, we study the scheduling problem with respect to age of information.

    List of papers
    1. Maximum Link Activation with Cooperative Transmission and Interference Cancellation in Wireless Networks
    Open this publication in new window or tab >>Maximum Link Activation with Cooperative Transmission and Interference Cancellation in Wireless Networks
    2017 (English)In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 16, no 2, p. 408-421Article in journal (Refereed) Published
    Abstract [en]

    We address the maximum link activation problem in wireless networks with new features, namely when the transmitters can perform cooperative transmission, and the receivers are able to perform successive interference cancellation. In this new problem setting, which transmitters should transmit and to whom, as well as the optimal cancellation patterns at the receivers, are strongly intertwined. We present contributions along three lines. First, we provide a thorough tractability analysis, proving the NP-hardness as well as identifying tractable cases. Second, for benchmarking purposes, we deploy integer linear programming for achieving global optimum using off-theshelf optimization methods. Third, to overcome the scalability issue of integer programming, we design a sub-optimal but efficient optimization algorithm for the problem in its general form, by embedding maximum-weighted bipartite matching into local search. Numerical results are presented for performance evaluation, to validate the benefit of cooperative transmission and interference cancellation for maximum link activation and to demonstrate the effectiveness of the proposed algorithm.

    Place, publisher, year, edition, pages
    IEEE, 2017
    National Category
    Communication Systems Telecommunications
    Identifiers
    urn:nbn:se:liu:diva-112447 (URN)10.1109/TMC.2016.2546906 (DOI)000393808500009 ()
    Conference
    2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), September 2-5, Washington DC, DC, USA
    Note

    Funding agencies: Swedish Research Council; EU FP7 Marie Curie [324515, 329313]; National Science Foundation [CCF-0728966, CCF-1420651]; ONR [N000141410107]

    Available from: 2014-11-27 Created: 2014-11-27 Last updated: 2018-08-14Bibliographically approved
    2. Minimum-Time Link Scheduling for Emptying Wireless Systems: Solution Characterization and Algorithmic Framework
    Open this publication in new window or tab >>Minimum-Time Link Scheduling for Emptying Wireless Systems: Solution Characterization and Algorithmic Framework
    2014 (English)In: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 60, no 2, p. 1083-1100Article in journal (Refereed) Published
    Abstract [en]

    We consider a set of transmitter-receiver pairs, or links, that share a wireless medium and address the problem of emptying backlogged queues with given initial size at the transmitters in minimum time. The problem amounts to determining activation subsets of links, and their time durations, to form a minimum-time schedule. Scheduling in wireless networks has been studied under various formulations before. In this paper, we present fundamental insights and solution characterizations that include: 1) showing that the complexity of the problem remains high for any continuous and increasing rate function; 2) formulating and proving sufficient and necessary optimality conditions of two baseline scheduling strategies that correspond to emptying the queues using one-at-a-time or all-at-once strategies; and 3) presenting and proving the tractability of the special case in which the transmission rates are functions only of the cardinality of the link activation sets. These results are independent of physical-layer system specifications and are valid for any form of rate function. We then develop an algorithmic framework for the solution to this problem. The framework encompasses exact as well as sub-optimal, but fast, scheduling algorithms, all under a unified principle design. Through computational experiments, we finally investigate the performance of several specific algorithms from this framework.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2014
    Keywords
    Algorithm; optimality; scheduling; wireless networks
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-104836 (URN)10.1109/TIT.2013.2292065 (DOI)000330286100022 ()
    Available from: 2014-02-28 Created: 2014-02-28 Last updated: 2018-08-14
    3. Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks
    Open this publication in new window or tab >>Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks
    2016 (English)In: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 3, no 3, p. 322-331Article in journal (Other academic) Published
    Abstract [en]

    We consider a wireless network with a set of transmitter-receiver pairs, or links, that share a common channel, and address the problem of emptying finite traffic volume from the transmitters in minimum time. This, so called, minimum-time scheduling problem has been proved to be NP-hard in general. In this paper, we study a class of minimum-time scheduling problems in which the link rates have a particular structure. We show that global optimality can be reached in polynomial time and derive optimality conditions. Then we consider a more general case in which we apply the same approach and obtain an approximation as well as lower and upper bounds to the optimal solution. Simulation results confirm and validate our approach.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2016
    Keywords
    algorithm, interference, optimality, scheduling, wireless networks
    National Category
    Communication Systems Telecommunications
    Identifiers
    urn:nbn:se:liu:diva-112446 (URN)10.1109/TCNS.2015.2512678 (DOI)000384701100010 ()
    Note

    At the time for thesis presentation publication was in status: Manuscript

    Available from: 2014-11-27 Created: 2014-11-27 Last updated: 2019-07-15Bibliographically approved
    4. A general optimality condition of link scheduling for emptying a wireless network
    Open this publication in new window or tab >>A general optimality condition of link scheduling for emptying a wireless network
    2016 (English)In: 2016 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY, IEEE , 2016, p. 1446-1450Conference paper, Published paper (Refereed)
    Abstract [en]

    We consider link scheduling in wireless networks for emptying the queues of the source nodes, and provide a unified mathematical formulation that accommodates all meaningful settings of link transmission rates and network configurations. We prove that, any scheduling problem is equivalent to solving a convex problem defined over the convex hull of the rate region. Based on the fundamental insight, a general optimality condition is derived, that yields a unified treatment of optimal scheduling. Furthermore, we demonstrate the implications and usefulness of the result. Specifically, by applying the theoretical insight to optimality characterization and complexity analysis of scheduling problems, we can both unify and extend previously obtained results.

    Place, publisher, year, edition, pages
    IEEE, 2016
    Series
    IEEE International Symposium on Information Theory. Proceedings, ISSN 2157-8095, E-ISSN 2157-8117
    Keywords
    convex programming;radio links;radio networks;telecommunication scheduling;convex hull;convex problem;general optimality condition;link scheduling;link transmission rates;network configurations;optimal scheduling;source nodes;wireless network;Complexity theory;Information theory;Interference;Optimal scheduling;Processor scheduling;Scheduling;Wireless networks;complexity;optimality;scheduling;wireless networks
    National Category
    Computer Engineering Information Systems Software Engineering
    Identifiers
    urn:nbn:se:liu:diva-131357 (URN)10.1109/ISIT.2016.7541538 (DOI)000390098701102 ()
    Conference
    IEEE International Symposium on Information Theory (ISIT), 2016, Universitat Pompeu Fabra, Barcelona, Spain, July l0-l5, 2016
    Available from: 2016-09-15 Created: 2016-09-15 Last updated: 2018-08-14Bibliographically approved
  • 4.
    He, Qing
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Revisiting Optimal Link Activation and Minimum-Time Scheduling in Wireless Networks2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    With the popularity of wireless communications in the last two decades, data traffic is exponentially increasing and requests high speed transmission. However, the resources, in particular, spectrum and energy, are limited. Therefore, network optimization with the objective of utilizing radio resource as efficiently as possible is crucial to the sustainable development of wireless communications.

    Link activation and scheduling are two classic problems of access coordination and resource allocation for multiple links that share a common channel. The problems originate from the broadcast nature of wireless media and are of significance in more complicated cross-layer optimization problems. Although there is a rich amount of literature, the problems remain challenging and are extended by novel setups incorporating new interference management technologies.

    In this thesis, we revisit these two fundamental problems with the main methods of mathematical modelling and applied optimization. The first two papers address the scheduling problem that amounts to emptying a given amount of data in minimum time. We derive theoretical insights including problem complexity, optimality conditions, as well as problem approximation and algorithmic framework, in general and for a class of networks with a particular structure. In the third paper, we incorporate cooperative transmission and interference cancellation with maximum link activation. Theoretical results and algorithm development are provided. Simulation study shows the new setup brings significant performance gain in comparison with the conventional approach.

    List of papers
    1. Minimum-Time Link Scheduling for Emptying Wireless Systems: Solution Characterization and Algorithmic Framework
    Open this publication in new window or tab >>Minimum-Time Link Scheduling for Emptying Wireless Systems: Solution Characterization and Algorithmic Framework
    2014 (English)In: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 60, no 2, p. 1083-1100Article in journal (Refereed) Published
    Abstract [en]

    We consider a set of transmitter-receiver pairs, or links, that share a wireless medium and address the problem of emptying backlogged queues with given initial size at the transmitters in minimum time. The problem amounts to determining activation subsets of links, and their time durations, to form a minimum-time schedule. Scheduling in wireless networks has been studied under various formulations before. In this paper, we present fundamental insights and solution characterizations that include: 1) showing that the complexity of the problem remains high for any continuous and increasing rate function; 2) formulating and proving sufficient and necessary optimality conditions of two baseline scheduling strategies that correspond to emptying the queues using one-at-a-time or all-at-once strategies; and 3) presenting and proving the tractability of the special case in which the transmission rates are functions only of the cardinality of the link activation sets. These results are independent of physical-layer system specifications and are valid for any form of rate function. We then develop an algorithmic framework for the solution to this problem. The framework encompasses exact as well as sub-optimal, but fast, scheduling algorithms, all under a unified principle design. Through computational experiments, we finally investigate the performance of several specific algorithms from this framework.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2014
    Keywords
    Algorithm; optimality; scheduling; wireless networks
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-104836 (URN)10.1109/TIT.2013.2292065 (DOI)000330286100022 ()
    Available from: 2014-02-28 Created: 2014-02-28 Last updated: 2018-08-14
    2. Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks
    Open this publication in new window or tab >>Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks
    2016 (English)In: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 3, no 3, p. 322-331Article in journal (Other academic) Published
    Abstract [en]

    We consider a wireless network with a set of transmitter-receiver pairs, or links, that share a common channel, and address the problem of emptying finite traffic volume from the transmitters in minimum time. This, so called, minimum-time scheduling problem has been proved to be NP-hard in general. In this paper, we study a class of minimum-time scheduling problems in which the link rates have a particular structure. We show that global optimality can be reached in polynomial time and derive optimality conditions. Then we consider a more general case in which we apply the same approach and obtain an approximation as well as lower and upper bounds to the optimal solution. Simulation results confirm and validate our approach.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2016
    Keywords
    algorithm, interference, optimality, scheduling, wireless networks
    National Category
    Communication Systems Telecommunications
    Identifiers
    urn:nbn:se:liu:diva-112446 (URN)10.1109/TCNS.2015.2512678 (DOI)000384701100010 ()
    Note

    At the time for thesis presentation publication was in status: Manuscript

    Available from: 2014-11-27 Created: 2014-11-27 Last updated: 2019-07-15Bibliographically approved
    3. Maximum Link Activation with Cooperative Transmission and Interference Cancellation in Wireless Networks
    Open this publication in new window or tab >>Maximum Link Activation with Cooperative Transmission and Interference Cancellation in Wireless Networks
    2017 (English)In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 16, no 2, p. 408-421Article in journal (Refereed) Published
    Abstract [en]

    We address the maximum link activation problem in wireless networks with new features, namely when the transmitters can perform cooperative transmission, and the receivers are able to perform successive interference cancellation. In this new problem setting, which transmitters should transmit and to whom, as well as the optimal cancellation patterns at the receivers, are strongly intertwined. We present contributions along three lines. First, we provide a thorough tractability analysis, proving the NP-hardness as well as identifying tractable cases. Second, for benchmarking purposes, we deploy integer linear programming for achieving global optimum using off-theshelf optimization methods. Third, to overcome the scalability issue of integer programming, we design a sub-optimal but efficient optimization algorithm for the problem in its general form, by embedding maximum-weighted bipartite matching into local search. Numerical results are presented for performance evaluation, to validate the benefit of cooperative transmission and interference cancellation for maximum link activation and to demonstrate the effectiveness of the proposed algorithm.

    Place, publisher, year, edition, pages
    IEEE, 2017
    National Category
    Communication Systems Telecommunications
    Identifiers
    urn:nbn:se:liu:diva-112447 (URN)10.1109/TMC.2016.2546906 (DOI)000393808500009 ()
    Conference
    2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), September 2-5, Washington DC, DC, USA
    Note

    Funding agencies: Swedish Research Council; EU FP7 Marie Curie [324515, 329313]; National Science Foundation [CCF-0728966, CCF-1420651]; ONR [N000141410107]

    Available from: 2014-11-27 Created: 2014-11-27 Last updated: 2018-08-14Bibliographically approved
  • 5.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology. Department of Electrical and Computer Engineering, University of Maryland, USA.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology. Department of Electrical and Computer Engineering, University of Maryland, USA.
    Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks2016In: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 3, no 3, p. 322-331Article in journal (Other academic)
    Abstract [en]

    We consider a wireless network with a set of transmitter-receiver pairs, or links, that share a common channel, and address the problem of emptying finite traffic volume from the transmitters in minimum time. This, so called, minimum-time scheduling problem has been proved to be NP-hard in general. In this paper, we study a class of minimum-time scheduling problems in which the link rates have a particular structure. We show that global optimality can be reached in polynomial time and derive optimality conditions. Then we consider a more general case in which we apply the same approach and obtain an approximation as well as lower and upper bounds to the optimal solution. Simulation results confirm and validate our approach.

  • 6.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology. Department of Electrical and Computer Engineering, University of Maryland, USA.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Revisiting Minimum-Length Scheduling in Wireless Networks: An Algorithmic Framework2012In: International Symposium on Information Theory and its Applications (ISITA), 2012, Piscataway, NJ, USA: IEEE , 2012, p. 506-510Conference paper (Refereed)
    Abstract [en]

    We consider the problem of constructing the minimum length schedule required to empty a wireless network with queues of given size. In a recent work we have provided new fundamental insights towards its structure and complexity. Motivated by the problem computational complexity, we demonstrate here how a one-size-fits-all optimal algorithm cannot be expected and introduce a framework that decomposes the problem in two core sub-problems: Selecting which subset of wireless links to activate and for how long. This modular approach enables the construction of algorithms that can yield solutions ranging from simple and intuitive to exact optimal. We provide a comprehensive set of design strategies and results to elucidate how different combinations within the framework modules can be used to approach optimality.

  • 7.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    A general optimality condition of link scheduling for emptying a wireless network2016In: 2016 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY, IEEE , 2016, p. 1446-1450Conference paper (Refereed)
    Abstract [en]

    We consider link scheduling in wireless networks for emptying the queues of the source nodes, and provide a unified mathematical formulation that accommodates all meaningful settings of link transmission rates and network configurations. We prove that, any scheduling problem is equivalent to solving a convex problem defined over the convex hull of the rate region. Based on the fundamental insight, a general optimality condition is derived, that yields a unified treatment of optimal scheduling. Furthermore, we demonstrate the implications and usefulness of the result. Specifically, by applying the theoretical insight to optimality characterization and complexity analysis of scheduling problems, we can both unify and extend previously obtained results.

  • 8.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Department of Electrical and Computer Engineering, University of Maryland, USA.
    Maximum Link Activation with Cooperative Transmission and Interference Cancellation in Wireless Networks2017In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 16, no 2, p. 408-421Article in journal (Refereed)
    Abstract [en]

    We address the maximum link activation problem in wireless networks with new features, namely when the transmitters can perform cooperative transmission, and the receivers are able to perform successive interference cancellation. In this new problem setting, which transmitters should transmit and to whom, as well as the optimal cancellation patterns at the receivers, are strongly intertwined. We present contributions along three lines. First, we provide a thorough tractability analysis, proving the NP-hardness as well as identifying tractable cases. Second, for benchmarking purposes, we deploy integer linear programming for achieving global optimum using off-theshelf optimization methods. Third, to overcome the scalability issue of integer programming, we design a sub-optimal but efficient optimization algorithm for the problem in its general form, by embedding maximum-weighted bipartite matching into local search. Numerical results are presented for performance evaluation, to validate the benefit of cooperative transmission and interference cancellation for maximum link activation and to demonstrate the effectiveness of the proposed algorithm.

  • 9.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Ephremides, Anthony
    Univ Maryland, MD 20742 USA.
    On Optimal Link Scheduling with Deadlines for Emptying a Wireless Network2017In: 2017 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY (ISIT), IEEE , 2017, p. 461-465Conference paper (Refereed)
    Abstract [en]

    We consider link scheduling in wireless networks for emptying the queues at the transmitters in minimum time, with time constraints, or deadlines, for one or multiple individual links. We formulate the minimum-time scheduling problem with deadlines (MTSD) mathematically and derive the optimal activation order of the link sets in a schedule solution. Theoretical results are obtained, showing that the MTSD can be treated as the conventional minimum-time scheduling problem by "absorbing" the deadline constraints into the rate region where the scheduling problem is defined. By this approach, optimality characterization and geometric interpretation for the MTSD are provided. Furthermore, we extend the results to the MTSD in a general form that accommodates an arbitrary rate region.

  • 10.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. University of Maryland, MD 20742 USA.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. University of Maryland, MD 20742 USA.
    On Optimal Link Scheduling with Min-Max Peak Age of Information in Wireless Systems2016In: 2016 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    Freshness of information is of critical importance for a host of applications of wireless communications. In order to deliver information from multiple sources in a timely and fair fashion through a wireless channel, we propose optimizing the link scheduling strategy in respect of age of information, which is a newly introduced metric that measures how fresh information is. Specifically, we consider a set of co-channel links, each having a number of packets to be delivered, and address the problem that aims to find the optimal scheduling solution, such that the maximum peak age of information is minimized. We mathematically formulate this so-called min-max peak age scheduling problem (MPASP), and prove it is NP-hard. Theoretical insights including tractable cases and optimality properties are derived. For problem solution, an integer linear programming (ILP) formulation is proposed. We also develop a sub-optimal, but fast, algorithm to solve the problem with better scalability. Numerical study shows that, by employing the optimal schedule, the maximum peak age is significantly reduced in comparison to other classic scheduling strategies such as minimum-time scheduling.

  • 11.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Ephremides, Anthony
    Univ Maryland, MD 20742 USA.
    Optimal Link Scheduling for Age Minimization in Wireless Systems2018In: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 64, no 7, p. 5381-5394Article in journal (Refereed)
    Abstract [en]

    Information age is a recently introduced metric to represent the freshness of information in communication systems. We investigate age minimization in a wireless network and propose a novel approach of optimizing the scheduling strategy to deliver all messages as fresh as possible. Specifically, we consider a set of links that share a common channel. The transmitter at each link contains a given number of packets with time stamps from an information source that generated them. We address the link transmission scheduling problem with the objective of minimizing the overall age. This minimum age scheduling problem (MASP) is different from minimizing the time or the delay for delivering the packets in question. We model the MASP mathematically and prove it is NP-hard in general. We also identify tractable cases as well as optimality conditions. An integer linear programming formulation is provided for performance benchmarking. Moreover, a steepest age descent algorithm with better scalability is developed. Numerical study shows that, by employing the optimal schedule, the overall age is significantly reduced in comparison to other scheduling strategies.

  • 12.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. University of Maryland, MD 20742 USA.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. University of Maryland, MD 20742 USA.
    Optimizing Freshness of Information: On Minimum Age Link Scheduling in Wireless Systems2016In: 2016 14TH INTERNATIONAL SYMPOSIUM ON MODELING AND OPTIMIZATION IN MOBILE, AD HOC, AND WIRELESS NETWORKS (WIOPT), IEEE , 2016, p. 115-122Conference paper (Refereed)
    Abstract [en]

    There is a growing interest in age of information, which is a newly introduced metric that measures the freshness of information in communication systems. We investigate the age of information in wireless networks and propose the novel approach of optimizing the scheduling strategy to deliver the information as timely as possible. We consider a set of links that share a common channel, each containing a number of packets with time stamps, and address the scheduling problem with the objective of minimizing the overall information age. We model this problem mathematically and prove it is NP-hard in general. Fundamental insights including tractable cases and optimality conditions are presented. An integer linear programming formulation is provided for performance benchmarking. Moreover, a steepest age decent algorithm with better scalability is developed. Numerical study shows that, by employing the optimal schedule, the overall information age is significantly reduced in comparison to other scheduling strategies.

  • 13.
    Karipidis, Eleftherios
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. University of Maryland, MD 20742 USA.
    He, Qing
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Max-Min Power Control in Wireless Networks With Successive Interference Cancelation2015In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 14, no 11, p. 6269-6282Article in journal (Refereed)
    Abstract [en]

    We consider a wireless network comprising a number of cochannel (hence mutually interfering) links. We study the power control problem of maximizing the rate that all links can simultaneously support under a novel setup, where receivers have interference cancelation (IC) capabilities. The problem of allocating the transmitting power is intertwined with determining the links on which receivers can perform IC and the order of cancelations. We provide and prove the theoretical results of the problem complexity and structural properties. For the problem solution, we propose a mixed-integer linear programming framework that enables jointly determining the optimal power and the IC patterns using off-the-shelf algorithms. This allows for the accurate assessment of the potential of IC for power control. Extensive numerical results are presented for performance evaluation, demonstrating the benefit of deploying IC in power control.

  • 14.
    Lei, Lei
    et al.
    Univ Luxembourg, Luxembourg.
    Lagunas, Eva
    Univ Luxembourg, Luxembourg.
    Maleki, Sina
    Univ Luxembourg, Luxembourg.
    He, Qing
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Chatzinotas, Symeon
    Univ Luxembourg, Luxembourg.
    Ottersten, Bjorn
    Univ Luxembourg, Luxembourg.
    Energy Optimization for Full-Duplex Self-Backhauled HetNet with Non-Orthogonal Multiple Access2017In: 2017 IEEE 18TH INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS (SPAWC), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    Small cell densification and advanced multi-user access schemes are promising approaches to dramatically improve 5G system performance. Towards efficient spectrum usage in ultra-dense heterogeneous networks, spectrum reuse between backhauling and access links combined with full duplex is applied. This forms a full-duplex self-backhauled heterogeneous network (FS-HetNet). Considering co-channel interference caused by frequency reuse, and residual self interference due to imperfect interference cancellation in full duplex, interference management becomes a major issue in boosting network performance. In this paper, motivated by the emerging non-orthogonal multiple access (NOMA) for 5G, we consider a NOMA-based scheme to mitigate co-channel interference and achieve efficient spectrum utilization for FS-HetNet. We address an energy-saving problem for the considered network, aiming to satisfy all users data demand within a limited transmit duration by consuming minimum energy. In addition to the energy consumption in transmission, the consumed decoding energy due to signal processing in successive interference cancellation is also taken into account. We propose an energy-efficient and delay-constrained scheduling algorithm to jointly optimize transmit power, user clustering, and transmission duration. Numerical results demonstrate that the proposed approach outperforms previous schemes.

  • 15.
    Lei, Ming
    et al.
    Xi An Jiao Tong University, Peoples R China.
    Zhang, Xingjun
    Xi An Jiao Tong University, Peoples R China.
    Zhang, Tong
    Xi An Jiao Tong University, Peoples R China.
    Lei, Lei
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    He, Qing
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Successive Interference Cancellation for Throughput Maximization in Wireless Powered Communication Networks2016In: 2016 IEEE 84TH VEHICULAR TECHNOLOGY CONFERENCE (VTC FALL), IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    In wireless powered communication networks (WPCNs), each user node, e.g., wireless powered sensor, is capable of either harvesting energy from a power station or transmitting data to a sink node. In the previous works, time division multiple access (TDMA) is typically used for transmission scheduling in WPCNs, that is, only one node can transmit data in one time slot. The spectrum efficiency is therefore limited by this orthogonality in time-domain scheduling. In this paper, to maximize the throughput in WPCNs, we present a new scheduling approach for energy harvesting and data transmission. Unlike TDMA, we consider that multiple nodes can simultaneously transmit their data in the same time slot, and the signals are separated at the sink node by performing successive interference cancellation (SIC). We formulate the throughput maximization problem as a linear programming problem. For solving the large scale instances, we design an algorithmic framework based on column generation. Numerical results demonstrate that compared to the TDMA based scheduling approach, substantial throughput improvement is achieved by the proposed algorithm.

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