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  • 151. Shi, G.
    et al.
    Proutiere, Alexandre
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Baras, John S.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Emergent behaviors over signed random dynamical networks: Relative-state-flipping model2015Inngår i: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. PP, nr 99, artikkel-id 7349158Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study asymptotic dynamical patterns that emerge among a set of nodes interacting in a dynamically evolving signed random network, where positive links carry out standard consensus and negative links induce relative-state flipping. A sequence of deterministic signed graphs defines potential node interactions that take place independently. Each node receives a positive recommendation consistent with the standard consensus algorithm from its positive neighbors, and a negative recommendation defined by relative-state flipping from its negative neighbors. After receiving these recommendations, each node puts a deterministic weight to each recommendation, and then encodes these weighted recommendations in its state update through stochastic attentions defined by two Bernoulli random variables. We establish a number of conditions regarding almost sure convergence and divergence of the node states. We also propose a condition for almost sure state clustering for essentially weakly balanced graphs, with the help of several martingale convergence lemmas. Some fundamental differences on the impact of the deterministic weights and stochastic attentions to the node state evolution are highlighted between the current relative-stateflipping model and the state-flipping model considered in Shi et al., IEEE Transaction on Control of Network Systems, 2015.

  • 152.
    Shi, Guodong
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    How agreement and disagreement evolve over random dynamic networks2013Inngår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 31, nr 6, s. 1061-1071Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dynamics of an agreement protocol interacting with a disagreement process over a common random network is considered. The model can represent the spreading of true and false information over a communication network, the propagation of faults in a large-scale control system, or the development of trust and mistrust in a society. At each time instance and with a given probability, a pair of network nodes interact. At random each of the nodes then updates its state towards the state of the other node (attraction), away from the other node (repulsion), or sticks to its current state (neglect). Agreement convergence and disagreement divergence results are obtained for various strengths of the updates for both symmetric and asymmetric update rules. Impossibility theorems show that a specific level of attraction is required for almost sure asymptotic agreement and a specific level of repulsion is required for almost sure asymptotic disagreement. A series of sufficient and/or necessary conditions are then established for agreement convergence or disagreement divergence. In particular, under symmetric updates, a critical convergence measure in the attraction and repulsion update strength is found, in the sense that the asymptotic property of the network state evolution transits from agreement convergence to disagreement divergence when this measure goes from negative to positive. The result can be interpreted as a tight bound on how much bad action needs to be injected in a dynamic network in order to consistently steer its overall behavior away from consensus.

  • 153.
    Shi, Guodong
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Randomized Gossiping with Unreliable Communication: Dependent or Independent Node Updates2012Inngår i: 2012 IEEE 51st Annual Conference on Decision and Control (CDC), IEEE conference proceedings, 2012, s. 4846-4851Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper studies an asynchronous randomized gossip algorithm under unreliable communication. At each instance, two nodes are selected to meet with a given probability. When nodes meet, two unreliable communication links are established with communication in each direction succeeding with a time-varying probability. It is shown that two particularly interesting cases arise when these communication processes are either perfectly dependent or independent. Necessary and sufficient conditions on the success probability sequence are proposed to ensure almost sure consensus or ?-consensus. Weak connectivity is required when the communication is perfectly dependent, while double connectivity is required when the communication is independent. Moreover, it is proven that with odd number of nodes, average preserving turns from almost forever (with probability one for all initial conditions) for perfectly dependent communication, to almost never (with probability zero for almost all initial conditions) for the independent case. This average preserving property does not hold true for general number of nodes. These results indicate the fundamental role the node interactions have in randomized gossip algorithms.

  • 154. Shi, Guodong
    et al.
    Li, Bo
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Finite-Time Convergent Gossiping2016Inngår i: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 24, nr 5, s. 2814-2826Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Gossip algorithms are widely used in modern distributed systems, with applications ranging from sensor networks and peer-to-peer networks to mobile vehicle networks and social networks. A tremendous research effort has been devoted to analyzing and improving the asymptotic rate of convergence for gossip algorithms. In this work we study finite-time convergence of deterministic gossiping. We show that there exists a symmetric gossip algorithm that converges in finite time if and only if the number of network nodes is a power of two, while there always exists an asymmetric gossip algorithm with finite-time convergence, independent of the number of nodes. For n = 2(m) nodes, we prove that a fastest convergence can be reached in nm = n log(2) n node updates via symmetric gossiping. On the other hand, under asymmetric gossip among n = 2(m) + rnodes with 0 <= r <= 2(m), it takes at least mn + 2r node updates for achieving finite-time convergence. It is also shown that the existence of finite-time convergent gossiping often imposes strong structural requirements on the underlying interaction graph. Finally, we apply our results to gossip algorithms in quantum networks, where the goal is to control the state of a quantum system via pairwise interactions. We show that finite-time convergence is never possible for such systems.

  • 155. Shi, Guodong
    et al.
    Proutiere, Alexandre
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Baras, John S.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    The Evolution of Beliefs over Signed Social Networks2016Inngår i: Operations Research, ISSN 0030-364X, E-ISSN 1526-5463, Vol. 64, nr 3, s. 585-604Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the evolution of opinions (or beliefs) over a social network modeled as a signed graph. The sign attached to an edge in this graph characterizes whether the corresponding individuals or end nodes are friends (positive links) or enemies (negative links). Pairs of nodes are randomly selected to interact over time, and when two nodes interact, each of them updates its opinion based on the opinion of the other node and the sign of the corresponding link. This model generalizes the DeGroot model to account for negative links: when two adversaries interact, their opinions go in opposite directions. We provide conditions for convergence and divergence in expectation, in mean-square, and in almost sure sense and exhibit phase transition phenomena for these notions of convergence depending on the parameters of the opinion update model and on the structure of the underlying graph. We establish a no-survivor theorem, stating that the difference in opinions of any two nodes diverges whenever opinions in the network diverge as a whole. We also prove a live-or-die lemma, indicating that almost surely, the opinions either converge to an agreement or diverge. Finally, we extend our analysis to cases where opinions have hard lower and upper limits. In these cases, we study when and how opinions may become asymptotically clustered to the belief boundaries and highlight the crucial influence of (strong or weak) structural balance of the underlying network on this clustering phenomenon.

  • 156.
    Shi, Guodong
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Proutiere, Alexandre
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Randomized consensus with attractive and repulsive links2013Inngår i: 2013 IEEE 52nd Annual Conference on Decision and Control (CDC), IEEE conference proceedings, 2013, s. 2599-2604Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We study convergence properties of a randomized consensus algorithm over a graph with both attractive and repulsive links. At each time instant, a node is randomly selected to interact with a random neighbor. Depending on if the link between the two nodes belongs to a given subgraph of attractive or repulsive links, the node update follows a standard attractive weighted average or a repulsive weighted average, respectively. The repulsive update has the opposite sign of the standard consensus update. In this way, it counteracts the consensus formation and can be seen as a model of link faults or malicious attacks in a communication network, or the impact of trust and antagonism in a social network. Various probabilistic convergence and divergence conditions are established. A threshold condition for the strength of the repulsive action is given for convergence in expectation: when the repulsive weight crosses this threshold value, the algorithm transits from convergence to divergence. An explicit value of the threshold is derived for classes of attractive and repulsive graphs. The results show that a single repulsive link can sometimes drastically change the behavior of the consensus algorithm. They also explicitly show how the robustness of the consensus algorithm depends on the size and other properties of the graphs.

  • 157.
    Simonetto, Andrea
    et al.
    Delft Univ Technol, Delft Ctr Syst & Control, Mekelweg 2, NL-2628 CD Delft, Netherlands..
    Keviczky, Tamas
    Delft Univ Technol, Delft Ctr Syst & Control, Mekelweg 2, NL-2628 CD Delft, Netherlands..
    Johansson, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. Royal Inst Technol KTH, Sch Elect Engn, ACCESS Linnaeus Ctr, S-10044 Stockholm, Sweden..
    A Regularized Saddle-Point Algorithm for Networked Optimization with Resource Allocation Constraints2012Inngår i: 2012 IEEE 51ST ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2012, s. 7476-7481Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose a regularized saddle-point algorithm for convex networked optimization problems with resource allocation constraints. Standard distributed gradient methods suffer from slow convergence and require excessive communication when applied to problems of this type. Our approach offers an alternative way to address these problems, and ensures that each iterative update step satisfies the resource allocation constraints. We derive step-size conditions under which the distributed algorithm converges geometrically to the regularized optimal value, and show how these conditions are affected by the underlying network topology. We illustrate our method on a robotic network application example where a group of mobile agents strive to maintain a moving target in the barycenter of their positions.

  • 158. Soldati, P.
    et al.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Distributed cross-layer coordination of congestion control and resource allocation in S-TDMA wireless networks2008Inngår i: Wireless networks, ISSN 1022-0038, E-ISSN 1572-8196, Vol. 14, nr 6, s. 949-965Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider the problem of joint congestion control and resource allocation in spatial-TDMA wireless networks. The design problem is posed as a utility maximization problem subject to link rate constraints which involve both transmission scheduling and power allocation. Starting from the performance limitations of a centralized optimization based on global network information, we proceed systematically in our development of two distributed and transparent protocols that rely on local information only. In the process, we introduce a novel decomposition method for convex optimization, establish its convergence for the utility maximization problem, and demonstrate how it suggests a distributed solution based on TCP/AQM and incremental updates of the transmission schedule. We develop a two-step procedure for finding the schedule updates and suggest two schemes for distributed link scheduling and power control under realistic interference models. Although the final protocols are suboptimal, we isolate and quantify the performance losses incurred by each simplification and demonstrate strong performance in examples.

  • 159.
    Soldati, Pablo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Distributed optimization of end-to-end rates and radio resources in WiMax single-carrier networks2006Inngår i: GLOBECOM - IEEE Global Telecommunications Conference, 2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider the problem of joint end-to-end band-width allocation and radio resource management in WiMax single-carrier wireless networks. The design problem is posed as a utility maximization problem subject to link rate constraints which involve transmission scheduling and power allocation. Inspired by a centralized algorithm for solving the associated optimization problem, we proceed systematically in our development of distributed resource allocation mechanisms. Contrary to the centralized algorithm, the proposed solution is distributed and of low computational complexity, generates schedules of finite length and with fixed time-slot durations, and acts on local neighborhood information only. Although the final scheme is suboptimal, we isolate and quantify the performance losses incurred and demonstrate strong performance in examples.

  • 160.
    Soldati, Pablo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Proportionally fair allocation of end-to-end bandwidth in STDMA wireless networks2006Inngår i: Proceedings of the International Symposium on Mobile Ad Hoc Networking and Computing, 2006, nr MobiHoc), 200, s. 286-297Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider the problem of designing distributed mechanisms for joint congestion control and resource allocation in spatial-reuse TDMA wireless networks. The design problem is posed as a utility maximization subject to link rate constraints that involve both power allocation and transmission scheduling over multiple time-slots. Starting from the performance limits of a centralized optimization based on global network information, we proceed systematically in the development of distributed and transparent protocols. In the process, we introduce a novel decomposition method for convex optimization, establish its convergence for the utility maximization problem and demonstrate how it suggests a distributed solution based on flow control optimization and incremental updates of the transmission schedule. We develop a two-step procedure for finding the schedule updates and suggest two schemes for distributed channel reservation and power control under realistic interference models. Although the final protocols are suboptimal, we isolate and quantify the performance losses incurred by each simplification and demonstrate strong performance in examples.

  • 161.
    Soldati, Pablo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    A low-signalling scheme for distributed resource allocation in multi-cellular OFDMA systems2008Inngår i: GLOBECOM 2008 - 2008 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE   , 2008, s. 3718-3723Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper considers distributed protocol design for joint sub-carrier, transmission scheduling and power management in uplink/downlink multi-cellular OFDMA wireless networks. The optimal solution to this problem is hard to achieve, both in theory and in practice. We propose a fully decentralized resource allocation scheme combining decomposition methods for convex optimization with a strategic non-cooperative game formulation of the power and sub-carrier allocation subproblem. Although the final protocols are suboptimal, they drastically reduce computation time while maintaining the overall system performance close to the optimal, exhibiting strong robustness to multiple access interference. We validate the theoretical framework and quantify the performance with numerical examples.

  • 162.
    Soldati, Pablo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    A mathematical programming approach to deadline-constrained transmission scheduling in wireless HART networks2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper considers transmission scheduling of deadline-constrained data in a wirelessHART network. We develop a thematical programming formulation and discuss efficient scheduling heuristics. We use the framework to schedule transmissions in a non-trivial network, and show how our results can be used to study design trade-offs such the use of multiple channels and multiple access points.

  • 163.
    Soldati, Pablo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Reducing signaling and respecting time-scales in cross-layer protocols design for wireless networks2009Inngår i: GLOBECOM 2009 - 2009 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, 2009, s. 3984-3991Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Current proposals for joint power and rate allocation protocols in ad hoc networks require a large signaling overhead, and do not adhere to the natural time-scales of transport and power control mechanisms. We present a solution that overcomes these issues. We pose the protocol design as a network utility maximization problem and adopt primal decomposition techniques to devise a novel distributed cross-layer design for transport and physical layer that achieves the optimal network operation. Our solution has several attractive features compared to alternatives: it adheres to the natural time-scale separation between rapid power control updates and slower end-to-end rate adjustments; it allows simplified power control mechanisms with reduced signalling requirements, and distributed slow rate cross-layer signalling mechanisms; and it maintains feasibility at each iteration. We validate the theoretical framework and compare the solution alternatives with numerical examples.

  • 164.
    Soldati, Pablo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Fodor, Gabor
    Ericsson Research, Sweden.
    Sorrentino, Stefano
    Ericsson Research, Sweden.
    On pilot dimensioning in multicell single input multiple output systems2011Inngår i: 2011 IEEE GLOBECOM Workshops, GC Wkshps 2011, IEEE , 2011, s. 1382-1387Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Resource management schemes in multicell orthogonal frequency division multiplexing (OFDM) networks typically assume perfect channel knowledge at the transmitter or employ a statistical channel estimation error. In this paper we propose a model that explicitly captures the inherent tradeoff between the power allocated to transmitting data and pilot signals in multicell single input multiple output (SIMO) systems. We first study the asymptotic behavior of the required data power to reach a predefined signal-to-noise ratio (SNR) target as a function of the employed pilot power in a single OFDM cell, then develop a distributed multicell algorithm that strives to minimize the multi-cell sum data power with respect to a predefined signal-to-interference-and-noise-ratio (SINR) target vector. The results provide new insights in dimensioning the pilot and data transmit power levels and serve as a basis for developing distributed power control schemes in multicell systems.

  • 165.
    Soldati, Pablo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Zhang, Haibo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Deadline-constrained transmission scheduling and data evacuation in wireless HART networks2009Inngår i: Proceedings of ECC, 2009, s. 4320-4325Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Real-time data delivery is a critical issue in wirelessHART networks. This paper develops a novel mathematical programming framework for joint routing and link scheduling of deadline-constrained traffic in wirelessHART networks. The general framework explores dynamic network flows on a time-expanded graph model and can provide flexible solutions for a variety of real-time data delivery problems. Data evacuation, an important communication paradigm in wirelessHART networks, is a special case of this general framework. We establish the lower bound on evacuation time for line, multi-line and binary tree networks. Moreover, we design a novel scheduling algorithm for data evacuation in binary tree networks, and prove that this scheduling algorithm can always achieve the lower bound on evacuation time. We evaluate our scheduling algorithm through numerical simulations, and results show that our algorithm can always minimize the evacuation time with the least number of channels.

  • 166.
    Soldati, Pablo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Zhang, Haibo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Zou, Zhenhua
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Optimal Routing and Scheduling of Deadline-Constrained Traffic Over Lossy Networks2010Inngår i: 2010 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE GLOBECOM 2010, 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The traditionally wired automation infrastructure is quickly migrating to more flexible and scalable wireless solutions. To cope with the stringent requirements of process automation in terms of latency and reliability, the network resources must be optimized to ensure timely and reliable communication. This paper considers the joint routing and transmission scheduling problem for reliable real-time communication over lossy networks. Specifically, we impose a strict latency bound for packet delivery from source to destination, and devise optimal transmission scheduling policies that maximize the success probability of delivering the packet within the specified deadline. A solution to this problem allows to characterize the set of achievable latencies and packet reliability for a given network. We offer a complete understanding of the problem when erasure events on links are independent and follow a Bernoulli process. We consider both static and dynamic resource allocation policies, and compare them in numerical examples.

  • 167.
    Talebi Mazraeh Shahi, Mohammad Sadegh
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Zou, Zhenhua
    Ericsson Res, SE-16483 Stockholm, Sweden..
    Combes, Richard
    Cent Supelec L2S, Telecommun Dept, F-91192 Gif Sur Yvette, France..
    Proutiere, Alexandre
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Stochastic Online Shortest Path Routing: The Value of Feedback2018Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 63, nr 4, s. 915-930Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper studies online shortest path routing over multihop networks. Link costs or delays are time varying and modeled by independent and identically distributed random processes, whose parameters are initially unknown. The parameters, and hence the optimal path, can only be estimated by routing packets through the network and observing the realized delays. Our aim is to find a routing policy that minimizes the regret (the cumulative difference of expected delay) between the path chosen by the policy and the unknown optimal path. We formulate the problem as a combinatorial bandit optimization problem and consider several scenarios that differ in where routing decisions are made and in the information available when making the decisions. For each scenario, we derive a tight asymptotic lower bound on the regret that has to be satisfied by any online routing policy. Three algorithms, with a tradeoff between computational complexity and performance, are proposed. The regret upper bounds of these algorithms improve over those of the existing algorithms. We also assess numerically the performance of the proposed algorithms and compare it to that of existing algorithms.

  • 168. Teixeira, Andre
    et al.
    Ghadimi, Euhanna
    Shames, Iman
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    The ADMM Algorithm for Distributed Quadratic Problems: Parameter Selection and Constraint Preconditioning2016Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 64, nr 2, s. 290-305Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents optimal parameter selection and preconditioning of the alternating direction method of multipliers (ADMM) algorithm for a class of distributed quadratic problems, which can be formulated as equality-constrained quadratic programming problems. The parameter selection focuses on the ADMM step-size and relaxation parameter, while the preconditioning corresponds to selecting the edge weights of the underlying communication graph. We optimize these parameters to yield the smallest convergence factor of the iterates. Explicit expressions are derived for the step-size and relaxation parameter, as well as for the corresponding convergence factor. Numerical simulations justify our results and highlight the benefits of optimal parameter selection and preconditioning for the ADMM algorithm.

  • 169.
    Teixeira, André
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ghadimi, Euhanna
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Shames, Iman
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Optimal scaling of the ADMM algorithm for distributed quadratic programming2013Inngår i: 2013 IEEE 52nd Annual Conference on Decision and Control (CDC), IEEE conference proceedings, 2013, s. 6868-6873Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper addresses the optimal scaling of the ADMM method for distributed quadratic programming. Scaled ADMM iterations are first derived for generic equalityconstrained quadratic problems and then applied to a class of distributed quadratic problems. In this setting, the scaling corresponds to the step-size and the edge-weights of the underlying communication graph. We optimize the convergence factor of the algorithm with respect to the step-size and graph edge-weights. Explicit analytical expressions for the optimal convergence factor and the optimal step-size are derived. Numerical simulations illustrate our results.

  • 170. Trdlicka, J.
    et al.
    Hanzalek, Z.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Optimal flow routing in multi-hop sensor networks with real-time constraints through linear programming2007Inngår i: IEEE Symposium on Emerging Technologies and Factory Automation, ETFA, 2007, s. 924-931Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We have proposed an algorithm for optimal real-time routing in multi-hop communication networks for multi-source/multi-sink connection. The algorithm deals with various capacity constraints in terms of communication limits and real-time constraints expressed as deadline for each particular flow of data. The objective is to find the optimal routing in terms of energy consumption. The algorithm is based on a data flow model leading to Linear Programming formulation and therefore it ensures polynomial-time complexity. An extension handling simultaneous real-time and non real-time routing is added. An example of data collection from 100 nodes is presented and performance experiments illustrating time complexity in dependence on the number of nodes are given.

  • 171. Tzortzis, I.
    et al.
    Charalambous, C. D.
    Charalambous, Themistoklis
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Hadjicostis, C. N.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Approximation of Markov processes by lower dimensional processes2014Inngår i: Proceedings of the IEEE Conference on Decision and Control, IEEE conference proceedings, 2014, nr February, s. 4441-4446Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we investigate the problem of aggregating a given finite-state Markov process by another process with fewer states. The aggregation utilizes total variation distance as a measure of discriminating the Markov process by the aggregate process, and aims to maximize the entropy of the aggregate process invariant probability, subject to a fidelity described by the total variation distance ball. An iterative algorithm is presented to compute the invariant distribution of the aggregate process, as a function of the invariant distribution of the Markov process. It turns out that the approximation method via aggregation leads to an optimal aggregate process which is a hidden Markov process, and the optimal solution exhibits a water-filling behavior. Finally, the algorithm is applied to specific examples to illustrate the methodology and properties of the approximations.

  • 172. Tzortzis, Ioannis
    et al.
    Charalambous, Charalambos D.
    Charalambous, Themistoklis
    Hadjicostis, Christoforos N.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Approximation of Markov Processes by Lower Dimensional Processes via Total Variation Metrics2017Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 62, nr 3, s. 1030-1045Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this paper is to approximate a Finite-State Markov (FSM) process by another process defined on a lower dimensional state space, called the approximating process, with respect to a total variation distance fidelity criterion. The approximation problem is formulated as an optimization problem using two different approaches. The first approach is based on approximating the transition probability matrix of the FSM process by a lower-dimensional transition probability matrix, resulting in an approximating process which is a Finite-State Hidden Markov (FSHM) process. The second approach is based on approximating the invariant probability vector of the original FSM process by another invariant probability vector defined on a lower-dimensional state space. Going a step further, a method is proposed based on optimizing a Kullback-Leibler divergence to approximate the FSHM processes by FSM processes. The solutions of these optimization problems are described by optimal partition functions which aggregate the states of the FSM process via a corresponding water-filling solution, resulting in lower-dimensional approximating processes which are FSHM or FSM processes. Throughout the paper, the theoretical results are justified by illustrative examples that demonstrate our proposed methodology.

  • 173.
    Witrant, Emmanuel
    et al.
    University of Grenoble.
    Park, Pan Gun
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Time-delay estimation and finite-spectrum assignment for control over multi-hop WSN2010Inngår i: Wireless Network Based Control / [ed] Mazumder, S., Springer Verlag , 2010, s. 135-152Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 174.
    Witrant, Emmanuel
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Park, Pan Gun
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Predictive control over wireless multi-hop networks2007Inngår i: Proceedings Of The 2007 Ieee Conference On Control Applications, IEEE , 2007, s. 1037-1042Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Remote control over wireless multi-hop networks is considered. Time-varying delays for the transmission of sensor and control data over the wireless network are caused by a randomized multi-hop routing protocol. The characterstics of the routing protocol together with lower-layer network mechanisms give rise to a delay process with high variance and stepwise changing mean. A new predictive control scheme with a delay estimator is proposed in the paper. The estimator is based on a Kalman filter with a change detection algorithm. It is able to track the delay mean changes but efficiently attenuate the high frequency jitter The control scheme is analyzed and its implementation detailed. Network data from an experimental setup are used to illustrate the efficiency of the approach.

  • 175. Xiao, L.
    et al.
    Johansson, Mikael
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Boyd, S. P.
    Simultaneous routing and resource allocation via dual decomposition2004Inngår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 52, nr 7, s. 1136-1144Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In wireless data networks, the optimal routing of data depends on the link capacities which, in turn, are determined by the allocation of communications resources (such as transmit powers and bandwidths) to the links. The optimal performance of the network can only be achieved by simultaneous optimization of routing and resource allocation. In this paper, we formulate the simultaneous routing and resource allocation (SRRA) problem, and exploit problem structure to derive efficient solution methods. We use a capacitated multicommodity now model to describe the data flows in the network. We assume that the capacity of a wireless link is a concave and increasing function of the communications resources allocated to the link, and the communications resources for groups of links are limited. These assumptions allow us to formulate the SRRA problem as a convex optimization problem over the network flow variables and the communications variables. These two sets of variables are coupled only through the link capacity constraints. We exploit this separable structure by dual decomposition. The resulting solution method attains the optimal coordination of data routing in the network layer and resource allocation in the radio control layer via pricing on the link capacities.

  • 176.
    Xiao, L.
    et al.
    Dept. of Aeronautics and Astronautics, Stanford University.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Hindi, H.
    Systems and Practices Laboratory, PARC.
    Boyd, S.
    Electrical Engineering Department, Stanford University.
    Goldsmith, A.
    Electrical Engineering Department, Stanford University.
    Joint optimization of wireless communication and networked control systems2005Inngår i: SWITCHING AND LEARNING IN FEEDBACK SYSTEMS, 2005, Vol. 3355, s. 248-272Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider a linear system, such as an estimator or a controller, in which several signals are transmitted over wireless communication channels. With the coding and medium access schemes of the communication system fixed, the achievable bit rates axe determined by the allocation of communications resources such as transmit powers and bandwidths, to different channels. Assuming conventional uniform quantization and a standard white-noise model for quantization errors, we consider two specific problems. In the first, we assume that the linear system is fixed and address the problem of allocating communication resources to optimize system performance. We observe that this problem is often convex (at least, when we ignore the constraint that individual quantizers have an integral number of bits), hence readily solved. We describe a dual decomposition method for solving these problems that exploits the problem structure. We briefly describe how the integer bit constraints can be handled, and give a bound on how suboptimal these heuristics can be. The second problem we consider is that of jointly allocating communication resources and designing the linear system in order to optimize system performance. This problem is in general not convex. We present an iterative heuristic method based on alternating convex optimization over subsets of variables, which appeaxs to work well in practice.

  • 177. Yang, B.
    et al.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Distributed optimization: A Tutorial Overview2010Inngår i: Networked Control Systems / [ed] Bemporad, A.; Heemels, M.; Johansson, M., Berlin: Springer, 2010Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 178. Yang, Bo
    et al.
    Shen, Yanyan
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Chen, Cailian
    Guan, Xinping
    Opportunistic multichannel access with decentralized channel state information2015Inngår i: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 15, nr 2, s. 322-339Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper considers multiaccess control for the uplink in orthogonal frequency division multiple access wireless networks. To avoid the extensive information exchange associated with centralized approaches, we formulate the decentralized access control problem with the contention power constraint as a Bayesian game, mapping time-varying channel state information into contention strategies. By exploiting the problem structure, a strategy where users access the channels with probability one if the observed channel gain is above a predetermined threshold is shown to be optimal. It is also shown that the energy consumption of the threshold strategy will not exceed that of randomized strategies. The game is then equivalently reformulated as one of finding the threshold value in a distributed manner, and the existence and uniqueness of Bayesian Nash equilibria is established. A distributed algorithm based on Lagrange duality is proposed to approach the unique equilibrium, and the algorithm is shown to be globally stable. In a homogeneous system, the performance loss of the proposed scheme is proved to be bounded compared with a centralized channel allocation scheme. Contrary to other proposals, our method allows for heterogeneous channel state information and achieves a comparable throughput with reduced power.

  • 179. Yang, Bo
    et al.
    Shen, Yanyan
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Guan, Xinping
    Threshold-based Multichannel Access with Energy Constraint2010Inngår i: 2010 IEEE International Conference on Communications, 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper considers multiaccess control for the uplink in orthogonal-frequency-division-multiple-access (OFDMA) wireless networks. To avoid extensive information exchange with the access point in centralized approaches, we propose a distributed threshold-based scheme, where each user accesses multiple channels simultaneously based on a comparison between measured channel gains and a channel gain threshold. Each user will adapts its channel gain threshold based on local measurements of collision on each channel and the energy consumption for channel contention. The problem is formulated as a constrained non-cooperative game. We show existence and uniqueness of the Nash equilibrium. A gradient-based algorithm is proposed to update the channel gain threshold. Furthermore, the convergence of this algorithm is proved. In addition, for heterogeneous systems, our proposed scheme can maintain multiuser diversity gains considering the time-varying channel gain and energy consumption. Compared with peer distributed OFDMA schemes and random channel selection algorithms, our proposed schemes reduce overhead and achieve a higher throughput.

  • 180. Zhang, H.
    et al.
    Soldati, P.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Time- and Channel-Efficient Link Scheduling for Convergecast in WirelessHART Networks2011Inngår i: 2011 IEEE 13th International Conference on Communication Technology (ICCT), 2011, s. 99-103Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fast convergecast is a critical functionality for wireless networks deployed for industrial monitoring and control. We address the time- and channel-optimal link scheduling problem for convergecast in multi-line networks, operating according to the recent WirelessHART standard. We first establish the lower bound on convergecast time and the lower bound on the number of channels for time-optimal convergecast. Then we present optimal scheduling policy for time-optimal convergecast and near-optimal policy for jointly time- and channel-optimal convergecast. Numerical and simulation results show that our scheme can provide fast convergecast inWirelessHART networks.

  • 181. Zhang, Haibo
    et al.
    Osterlind, Fredrik
    Soldati, Pablo
    Voigt, Thiemo
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Time-Optimal Convergecast With Separated Packet Copying: Scheduling Policies and Performance2015Inngår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 64, nr 2, s. 793-803Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Convergecast, in which packets originating from multiple sources are reported to a single sink, is a fundamental primitive for data collection in wireless sensor networks. This paper investigates the time-optimal link-scheduling problem for time-division multiple-access (TDMA)-based convergecast, aiming to minimize the amount of time required to complete convergecast. We observe that packet copying between the microcontroller and the radio transceiver in existing sensor platforms has a big impact on the packet forwarding delay, and we propose a novel model for convergecast in which packet copying is separated from packet transmission and reception. We establish tight lower bounds on the number of time slots required for convergecast in networks with line and tree routing topologies, and we present both centralized and distributed algorithms for constructing the time-optimal convergecast schedules. We evaluate our scheme in both simulations and experiments on hardware. The results show that our scheme can achieve a system throughput (defined as the number of data bits received by the sink per second) of 202.8 kb/s, which is 86.31% of the theoretical bound. In comparison with the traditional TDMA-based convergecast schemes, our scheme can achieve up to a 86.22% improvement on system throughput.

  • 182.
    Zhang, Haibo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Soldati, Pablo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Optimal Link Scheduling and Channel Assignment for Convergecast in Linear Wireless HART Networks2009Inngår i: 2009 7TH INTERNATIONAL SYMPOSIUM ON MODELING AND OPTIMIZATION IN MOBILE, AD HOC, AND WIRELESS, NEW YORK: IEEE , 2009, s. 82-89Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Convergecast, in which data from a set of sources is routed toward one data sink, is a critical functionality for wireless networks deployed for industrial monitoring and control. We address the joint link scheduling and channel assignment problem for convergecast in networks operating according to the recent WirelessHART standard. For a linear network with N single-buffer devices, we demonstrate that the minimum time to complete convergecast is 2N - 1 time-slots, and that the minimum number of channels required for this operation is inverted right perpendicularN/2inverted left perpendicular. When the devices are allowed to buffer multiple packets, we prove that the optimal convergecast time remains the same while the number of required channels can be reduced to inverted right perpendicularN - root N-(N-1)/2inverted left perpendicular. For both cases, we present jointly time- and channel-optimal scheduling policies with complexity O(N-2). Numerical results demonstrate that our schemes are also efficient in terms of memory utilization.

  • 183. Zhang, Haibo
    et al.
    Soldati, Pablo
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Performance Bounds and Latency-Optimal Scheduling for Convergecast in WirelessHART Networks2013Inngår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 12, nr 6, s. 2688-2696Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Convergecast, in which data from a set of source devices is delivered to a single data sink, is a critical functionality in networks deployed for industrial monitoring and control. We address the latency-optimal link scheduling problem for convergecast in networks operating according to the recent WirelessHART standard. When there is no restriction on the number of channels, we present a latency-optimal scheduling policy in which each routing node is required to buffer at most one packet at any point in time. For networks with a limited number of channels, we first establish a lower bound on the number of channels for latency-optimal convergecast and a lower bound on latency for convergecast using a fixed number of channels, and then present a heuristic scheme for channel-constrained latency-optimal convergecast scheduling. Simulation results confirm that, at much modest computational cost, our heuristic scheme can construct convergecast schedules with latency close to that of the optimal schedules.

  • 184.
    Zhang, Haibo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Österlind, F.
    Soldati, Pablo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Voigt, T.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Rapid convergecast on commodity hardware: Performance limits and optimal policies2010Inngår i: SECON 2010 - 2010 7th Annual IEEE Communications Society Conference on Sensor, 2010, Vol. Mesh and Ad Hoc Communications and NetworksKonferansepaper (Fagfellevurdert)
    Abstract [en]

    The increased industrial interest in wireless sensor networks demands a shift from optimizing protocols for reporting sporadic events, to solutions for high-rate data collection and dissemination. We study time-optimal convergecast under the communication constraints of commodity sensor network platforms. We propose a novel convergecast model in which packet copying between the microcontroller and the radio transceiver is separated from packet transmission, thereby improving channel utilization and system throughput. Based on this model, we establish the tight lower bound on the number of time slots for convergecast in networks with tree routing topology, and present both centralized and distributed algorithms for computing time-optimal convergecast schedules. Our scheme is memory-efficient as each node buffers at most one packet at any time. We evaluate our scheme in simulation and on real hardware, and show that our scheme can achieve a throughput of 203 kbit/s (86.4% of the theoretical upper bound): up to 86.24 % improvement compared with traditional TDMA-based convergecast. With an optimal routing tree and the maximum MAC layer payload, convergecast in a network with 20 sensor nodes can be completed in only 100ms.

  • 185.
    Zou, Zhenhua
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Demirel, Burak
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Minimum-energy packet forwarding policies for guaranteed LQG performance in wireless control systems2012Inngår i: 2012 IEEE 51st Annual Conference on Decision and Control (CDC), IEEE , 2012, s. 3341-3346Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper studies minimum-energy packet forwarding policies for communicating sensor measurements from plant to controller over an unreliable multi-hop wireless network so as to guarantee that the optimal controller achieves a prespecified closed-loop performance. For fixed sampling interval, we demonstrate that the minimal linear-quadratic control loss is monotonically decreasing in the reliability of the sensor-to-controller communication. This allows us to decompose the overall design problem into two separate tasks: finding the minimum end-to-end reliability that allows to achieve a prespecified linear-quadratic loss, and developing minimum-energy packet forwarding policies under a deadline-constrained reliability requirement. We develop optimal solutions for both subproblems and show how the co-designed system with minimum forwarding energy cost and guaranteed LQG control performance can be found by a one-dimensional search over admissible sampling periods. The paper ends with a numerical example which demonstrates the effectiveness of the proposed framework.

  • 186.
    Zou, Zhenhua
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Deadline-constrained maximum reliability packet forwarding with limited channel state information2013Inngår i: 2013 IEEE Wireless Communications and Networking Conference (WCNC), New York: IEEE Communications Society, 2013, s. 1721-1726Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper considers real-time packet forwarding over wireless multi-hop networks with lossy and bursty links. Our objective is to maximize the probability that individual packets reach their destination before a hard deadline. The loss processes on links are modeled by finite-state Markov chains. While the parameters of the Markov chains are assumed to be known, the instantaneous channel states are not accessible but have to be estimated from observations of successes and failures of actual packet transmissions. We formulate the forwarding problem as a partially observable Markov decision process and derive the optimal forwarding policy. A novel technique, based on maximum-volume inscribed ellipsoids, for computing approximate solutions with reduced implementation complexity is proposed. We further discuss structural properties of the value function and the optimal actions. Finally, numerical examples illustrate the power of the developed techniques.

  • 187.
    Zou, Zhenhua
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Minimum-energy packet forwarding over lossy networks under deadline and reliability constraints2012Inngår i: 10th International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks (WiOpt),2012, IEEE conference proceedings, 2012, s. 224-231Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper studies minimum-energy packet forwardingover multi-hop lossy networks under deadline andreliability constraints. We assume a routing topology in theform of a directed graph with packet loss processes on linksdescribed by finite-state Markov chains, and formulate the forwardingproblem as a finite-horizon constrained Markov decisionprocess. We show that the minimum energy forwarding policyunder hard deadline and reliability constraint can be computedusing dynamic programming, and that the optimal forwardingpolicy is a randomized policy over two history-independent anddeterministic policies. Closed-form optimal policies are derivedfor some particular scenarios. Numerical examples show thatthe transmission energy cost of achieving reliabilities close to themaximum can be significant when links are bursty. In addition,transmission power adjustments can further reduce energy cost.Finally, we develop simple heuristic policies with a good balancebetween transmission energy cost and reliability.

  • 188.
    Zou, Zhenhua
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Proutiere, Alexandre
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Online shortest path routing: The value of information2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper studies online shortest path routing over dynamic multi-hop networks. Link costs or delays are time-varying and modelled by independent and identically distributed random processes, whose parameters are initially unknown. The parameters, and hence the optimal path, can only be estimated by routing packets through the network and observing the realized delays. Our aim is to find a routing policy that minimizes the regret (the cumulative delay difference) between the path chosen by the policy and the unknown optimal path. We formulate the problem as a combinatorial bandit optimization problem and consider several scenarios that differ in where routing decisions are made and in the information available when making the decision. For each scenario, we derive the tight asymptotic lower bound on the regret that has to be satisfied by any online routing policy. These bounds help us to understand the performance improvements we can expect when (i) taking routing decisions at each hop rather than at the source only, and (ii) observing per-link costs rather than aggregate path costs. In particular, we show that (i) is of no use while (ii) can have a spectacular impact. Efficient algorithms are proposed and evaluated against the state-of-the a

     

  • 189.
    Zou, Zhenhua
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Soldati, Pablo
    KTH, Skolan för elektro- och systemteknik (EES).
    Zhang, Haibo
    KTH, Skolan för elektro- och systemteknik (EES).
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Delay-constrained maximum reliability routing over lossy links2010Inngår i: Proceedings of the IEEE Conference on Decision and Control, IEEE , 2010, s. 973-978Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper studies the problem of joint routing and transmission scheduling for reliable real-time communication over lossy networks. We impose a strict latency bound on the packet delivery from source to destination and develop transmission scheduling policies that maximize the probability that the packet is delivered within the specified deadline. A solution to this problem allows to characterize the set of achievable latencies and packet loss probabilities for a given network. We develop dynamic programming-based solutions for deadline-constrained maximum reliability routing under Bernoulli and Gilbert-Elliot packet loss models. Particular instances of the problem that admit numerically efficient solutions are discussed and our results are demonstrated on several examples.

  • 190.
    Zou, Zhenhua
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Soldati, Pablo
    Huawei Technologies Sweden AB.
    Zhang, Haibo
    University of Otago, New Zealand.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Energy-efficient deadline-constrained maximum reliability forwarding in lossy networks2012Inngår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 11, nr 10, s. 3474-3483Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper studies the problem of optimal forwarding for reliable and energy-efficient real-time communication over multi-hop wireless lossy networks. We impose a strict per-packet latency bound and develop forwarding policies that maximize the probability that the packet is delivered within the specified deadline minus a transmission energy cost. A solution to this problem allows to characterize the set of achievable latency-reliability pairs and to trace out the Pareto frontier between achievable deadline-constrained reliability and transmission energy cost. We develop dynamic programming-based solutions under a finite-state Markov channel model. Particular instances with Bernoulli and Gilbert-Elliot loss models that admit numerically efficient solutions are discussed and our results are demonstrated on several examples.

  • 191. Årzén, Karl-Erik
    et al.
    Robertsson, Anders
    Henriksson, Dan
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Hjalmarsson, Håkan
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Conclusions from the European Roadmap on Control of Computing Systems2006Inngår i: First International Workshop on Feedback Control Implementation and Design in Computing Systems and Networks, 2006Konferansepaper (Fagfellevurdert)
  • 192. Årzén, Karl-Erik
    et al.
    Robertsson, Anders
    Henriksson, Dan
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Conclusions of the ARTIST2 roadmap on control of computing systems2006Inngår i: ACM SIGBED Review, ISSN 1551-3688, Vol. 3, nr 2, s. 11-20Artikkel i tidsskrift (Fagfellevurdert)
  • 193.
    Åstrand, Max
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. ABB Corp Res, Control Optimizat & Analyt, Automat Solut, Vasteras, Sweden.
    Johansson, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Greberg, J.
    Lulea Univ Technol, Dept Civil Environm & Nat Resources Engn, Div Min & Geotech Engn, Lulea, Sweden..
    Underground mine scheduling modelled as a flow shop: a review of relevant work and future challenges2018Inngår i: The Southern African Journal of Mining and Metallurgy, ISSN 2225-6253, E-ISSN 1543-9518, Vol. 118, nr 12, s. 1265-1276Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Advanced planning and automation are increasingly important in modern mines. Sophisticated methods for long-term mine planning are often used, and the advent of autonomous machines makes the actual operation more predictable. However, the interface between these two timescales, i.e. the scheduling of the mobile production fleet, often limits the ability to operate mines at maximum profitability. We show how scheduling the production fleet in an underground mine can be modelled as a flow shop. A flow shop is a general abstract process formulation that captures the key properties of a scheduling problem without going into specific details. Thus, the flow shop enables mine scheduling to reap the benefits of scheduling research from other industries. We review recent results from the mining community and the flow shop community, and introduce scheduling methods used in these two fields. This work aims at providing value to researchers from the mining community who want to leverage their skill set, as well as to theoretical researchers by presenting the mining process as a potential application area. Lastly, we discuss the results, and outline some future challenges and opportunities facing the industry.

  • 194.
    Åstrand, Max
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. ABB Corporate Research Center, Västerås, Sweden.
    Johansson, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Zanarini, A.
    Fleet scheduling in underground mines using constraint programming2018Inngår i: 15th International Conference on Integration of Constraint Programming, Artificial Intelligence, and Operations Research, CPAIOR 2018, Springer, 2018, Vol. 10848, s. 605-613Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The profitability of an underground mine is greatly affected by the scheduling of the mobile production fleet. Today, most mine operations are scheduled manually, which is a tedious and error-prone activity. In this contribution, we present and formalize the underground mine scheduling problem, and propose a CP-based model for solving it. The model is evaluated on instances generated from real data. The results are promising and show a potential for further extensions.

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