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  • 101.
    Ghauch, Hadi
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Kim, Taejoon
    Univ Kansas, Dept EECS, Lawrence, KS 66045 USA..
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Skoglund, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Compressive Sensing with Applications to Millimeter-wave Architectures2019In: 2019 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING (ICASSP), IEEE , 2019, p. 7834-7838Conference paper (Refereed)
    Abstract [en]

    To make the system available at low-cost, millimeter-ave (mmWave) multiple-input multiple-output (MIMO) architectures employ analog arrays, which are driven by a limited number of radio frequency (RF) chains. One primary challenge of using large hybrid analog-digital arrays is that the digital baseband cannot directly access the signal to/from each antenna. To address this limitation, recent research has focused on retransmissions, iterative precoding, and subspace decomposition methods. Unlike these approaches that exploited the channel's low-rank, in this work we exploit the sparsity of the received signal at both the transmit/receive antennas. While the signal itself is de facto dense, it is well-known that most signals are sparse under an appropriate choice of basis. By delving into the structured compressive sensing (CS) framework and adapting them to variants of the mmWave hybrid architectures, we provide methodologies to recover the analog signal at each antenna from the (low-dimensional) digital signal. Moreover, we characterizes the minimal numbers of measurement and RF chains to provide this recovery, with high probability. We discuss their applications to common variants of the hybrid architecture. By leveraging the inherent sparsity of the received signal, our analysis reveals that a hybrid MIMO system can be " turned into" a fully digital one: the number of needed RF chains increases logarithmically with the number of antennas.

  • 102.
    Ghauch, Hadi
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Kim, Taejoon
    KTH, School of Electrical Engineering and Computer Science (EECS). City University of Hong Kong.
    Skoglund, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Low-Overhead Coordination in Sub-28 Millimeter-Wave Networks2018In: 2018 IEEE International Conference on Communications (ICC), 2018Conference paper (Refereed)
  • 103. Gkatzikis, L.
    et al.
    Sourlas, V.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Koutsopoulos, I.
    Low complexity content replication through clustering in Content-Delivery Networks2017In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 121, p. 137-151Article in journal (Refereed)
    Abstract [en]

    Contemporary Content Delivery Networks (CDN) handle a vast number of content items. At such a scale, the replication schemes require a significant amount of time to calculate and realize cache updates, and hence they are impractical in highly-dynamic environments. This paper introduces cluster-based replication, whereby content items are organized in clusters according to a set of features, given by the cache/network management entity. Each cluster is treated as a single item with certain attributes, e.g., size, popularity, etc. and it is then altogether replicated in network caches so as to minimize overall network traffic. Clustering items reduces replication complexity; hence it enables faster and more frequent caches updates, and it facilitates more accurate tracking of content popularity. However, clustering introduces some performance loss because replication of clusters is more coarse-grained compared to replication of individual items. This tradeoff can be addressed through proper selection of the number and composition of clusters. Due to the fact that the exact optimal number of clusters cannot be derived analytically, an efficient approximation method is proposed. Extensive numerical evaluations of time-varying content popularity scenarios allow to argue that the proposed approach reduces core network traffic, while being robust to errors in popularity estimation.

  • 104.
    Gkatzikis, Lazaros
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Sourlas, Vasilis
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Koutsopoulos, Iordanis
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Clustered Content Replication for Hierarchical Content Delivery Networks2015In: 2015 IEEE International Conference On Communications (ICC), 2015, Vol. 2015, p. 5872-5877Conference paper (Refereed)
    Abstract [en]

    Caching at the network edge is considered a promising solution for addressing the ever-increasing traffic demand of mobile devices. The problem of proactive content replication in hierarchical cache networks, which consist of both network edge and core network caches, is considered in this paper. This problem arises because network service providers wish to efficiently distribute content so that user-perceived performance is maximized. Nevertheless, current high-complexity replication algorithms are impractical due to the vast number of involved content items. Clustering algorithms inspired from machine learning can be leveraged to simplify content replication and reduce its complexity. Specifically, similar items could be clustered together, e.g., according to their popularity in space and time. Replication on a cluster-level is a problem of substantially smaller dimensionality, but it may result in suboptimal decisions compared to item-level replication. The factors that cause performance loss are identified and a clustering scheme that addresses the specific challenges of content replication is devised. Extensive numerical evaluations, based on realistic traffic data, demonstrate that for reasonable cluster sizes the impact on actual performance is negligible.

     

  • 105.
    Jakobsson, Martin
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A Comparative Analysis of the Fast-Lipschitz Convergence Speed2012In: 2012 IEEE 51st Annual Conference on Decision and Control (CDC), IEEE conference proceedings, 2012, p. 7464-7469Conference paper (Refereed)
    Abstract [en]

    Fast-Lipschitz optimization is a recently proposed framework useful for an important class of centralized and distributed optimization problems over peer-to-peer networks. The properties of Fast-Lipschitz problems allow to compute the solution without having to introduce Lagrange multipliers, as in most other methods. This is highly beneficial, since multipliers need to be communicated across the network and thus increase the communication complexity of solution algorithms. Although the convergence speed of Fast-Lipschitz optimization methods often outperforms Lagrangian methods in practice, there is not yet a theoretical analysis. This paper provides a fundamental step towards such an analysis. Sufficient conditions for superior convergence of the Fast-Lipschitz method are established. The results are illustrated by simple examples. It is concluded that optimization problems with quadratic cost functions and linear constraints are always better solved by Fast-Lipschitz optimization methods, provided that certain conditions hold on the eigenvalues of the Hessian of the cost function and constraints.

  • 106.
    Jakobsson, Martin
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Extensions of Fast-Lipschitz Optimizationfor Convex and Non-convex Problems2012In: IFAC Proceedings Volumes (IFAC-PapersOnline): Estimation and Control of Networked Systems, Volume 3, Part 1, 2012, p. 162-167Conference paper (Refereed)
    Abstract [en]

    Fast-Lipschitz optimization has been recently proposed as a new framework with numerous computational advantages for both centralized and decentralized convex and non-convex optimization problems. Such a framework generalizes the interference function optimization, which plays an essential role distributed radio power optimization over wireless networks. The characteristics of Fast-Lipschitz methods are low computational and coordination complexity compared to Lagrangian methods, with substantial benefits particularly for distributed optimization. These special properties of Fast-Lipschitz optimization can be ensured through qualifying conditions, which allow the Lagrange multipliers to be bound away from zero. In this paper, the Fast-Lipschitz optimization is substantially extended by establishing new qualifying conditions. The results are a generalization of the old qualifying conditions and a relaxation of the assumptions on problem structure so that the optimization framework can be applied to many more problems than previously possible. The new results are illustrated by a non-convex optimization problem, and by a radio power optimization problem which cannot be handled by the existing Fast-Lipschitz theory.

  • 107. Jakobsson, Martin
    et al.
    Magnusson, Sindri
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Weeraddana, Pradeep Chathuranga
    Sri Lankan Institute of Information Technology.
    Extensions of Fast-Lipschitz Optimization2016In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 61, no 4, p. 861-876Article in journal (Refereed)
    Abstract [en]

    The need of fast distributed solvers for optimizationproblems in networked systems has motivated the recent developmentof the Fast-Lipschitz optimization framework. In such an optimization, problems satisfying certain qualifying conditions,such as monotonicity of the objective function and contractivityof the constraints, have a unique optimal solution obtained via fast distributed algorithms that compute the fixed point of the constraints. This paper extends the set of problems for which the Fast-Lipschitz framework applies. Existing assumptions on the problem form are relaxed and new and generalized qualifying conditions are established by novel results based on Lagrangianduality. It is shown for which cases of more constraints thandecision variables, and less constraints than decision variables Fast-Lipschitz optimization applies. New results are obtained by imposing non strict monotonicity of the objective functions. The extended Fast-Lipschitz framework is illustrated by a number ofexamples, including network optimization and optimal control problems.

  • 108.
    Jiang, Xiaolin
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Pang, Zhibo
    ABB Corp Res Ctr, Wireless Commun, Vasteras, Sweden..
    Luvisotto, Michele
    ABB Corp Res Ctr, Vasteras, Sweden..
    Pan, Fei
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Commun & Informat Syst, Chengdu, Sichuan, Peoples R China..
    Candell, Richard
    NIST, Gaithersburg, MD 20899 USA..
    Fischione, Carlos
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering. Synopsys, Mountain View, CA USA.;United Technol Res Ctr, E Hartford, CT 06108 USA..
    Using a Large Data Set to Improve Industrial Wireless Communications Latency, Reliability, and Security2019In: IEEE Industrial Electronics Magazine, ISSN 1932-4529, E-ISSN 1941-0115, Vol. 13, no 1, p. 6-12Article in journal (Refereed)
    Abstract [en]

    Trealize the Industry 4.0 vision and enable mobile connectivity and flexible deployment in harsh industrial environments, wireless communication is essential. But before wireless communications technology can be widely deployed for critical control applications, first it must be assessed, and that requires a comprehensive characterization of the wireless channel. This can be done by analyzing large amounts of wireless data collected from different industrial environments. In this article, we discuss the possibilities offered by a recently published industrial wireless data set. This data set is more exhaustive than measurements previously reported. We show two cases of how those data have been applied to improve latency performance and to investigate the feasibility of physical-layer security techniques for wireless communication in industrial environments.

  • 109.
    Jiang, Xiaolin
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Pang, Zhibo
    ABB Corporate Research, Sweden.
    N. Jansson, Roger
    ABB Corporate Research, Sweden.
    Pan, Fei
    University of Electronic Science and Technology of China, China.
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Fundamental Constraints for Time-slotted MAC Design in Wireless High Performance : the Realistic Perspective of Timing2018Conference paper (Refereed)
  • 110.
    Jiang, Xiaolin
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Pang, Zhibo
    Zhan, Ming
    Dzung, Dacfey
    Luvisotto, Michele
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Packet Detection by a Single OFDM Symbol in URLLC for Critical Industrial Control: A Realistic Study2019In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 37, no 4, p. 933-946Article in journal (Refereed)
    Abstract [en]

    Ultra-high reliable and low-latency communication (URLLC)is envisaged to support emerging applications with strict latency and reliability requirements. Critical industrial control is among the most important URLLC applications where the stringent requirements make the deployment of wireless networks critical, especially as far as latency is concerned. Since the amount of data exchanged in critical industrial communications is generally small, an effective way to reduce the latency is to minimize the packet's synchronization overhead, starting from the physical layer (PHY). This paper proposes to use a short one-symbol PHY preamble for critical wireless industrial communications, reducing significantly the transmission latency with respect to other wireless standards. Dedicated packet detection and synchronization algorithms are discussed, analyzed, and tuned to ensure that the required reliability level is achieved with such extremely short preamble. Theoretical analysis, simulations, and experiments show that detection error rates smaller than 10(-6) can be achieved with the proposed preamble while minimizing the latencies.

  • 111.
    Jiang, Xiaolin
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Pang, Zhibo
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Zhan, Ming
    KTH.
    Dzung, Dacfey
    Luvisotto, Michele
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Packet Detection by Single OFDM Symbol in URLLC for Critical Industrial Control: a Realistic Study2018In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008Article in journal (Other academic)
  • 112.
    Jiang, Xiaolin
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Shokri-Ghadikolaei, Hossein
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Pang, Z.
    A simplified interference model for outdoor millimeter wave networks2018In: 9th International Conference on Wireless Internet, WICON 2016, Springer, 2018, Vol. 214, p. 101-108Conference paper (Refereed)
    Abstract [en]

    Industry 4.0 is the emerging trend of the industrial automation. Millimeter-wave (mmWave) communication is a prominent technology for wireless networks to support the Industry 4.0 implementation. The availability of tractable accurate interference models would greatly facilitate the design of these networks. In this paper, we investigate the accuracy of an interference model that assumes impenetrable obstacles and neglects the sidelobes. We quantify the error of such a model in terms of statistical distribution of the signal to noise plus interference ratio for outdoor mmWave networks under different antenna array settings. The results show that assuming impenetrable obstacle comes at almost no accuracy penalty, and the accuracy of neglecting antenna sidelobes can be guaranteed with sufficiently large number of antenna elements.

  • 113.
    Jiang, Xiaolin
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering. KTH.
    Shokri-Ghadikolaei, Hossein
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Pang, Zhibo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    A Simplified Interference Model for Outdoor Millimeter-waveNetworks2019In: Mobile Networks and Applications, ISSN 1383-469X, Vol. 24, no 3, p. 983-990Article in journal (Refereed)
    Abstract [en]

    Industry 4.0 is the emerging trend of the industrial automation. Millimeter-wave (mmWave) communication is a prominent technology for wireless networks to support the Industry 4.0 requirements. The availability of tractable accurate interference models would greatly facilitate performance analysis and protocol development for these networks. In this paper, we investigate the accuracy of an interference model that assumes impenetrable obstacles and neglects the sidelobes. We quantify the error of such a model in terms of statistical distribution of the signal to noise plus interference ratio and of the user rate for outdoor mmWave networks under different carrier frequencies and antenna array settings. The results show that assuming impenetrable obstacle comes at almost no accuracy penalty, and the accuracy of neglecting antenna sidelobes can be guaranteed with sufficiently large number of antenna elements. The comprehensive discussions of this paper provide useful insights for the performance analysis and protocol design of outdoor mmWave networks.

  • 114.
    Jiang, Xiaolin
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Shokri-Ghadikolaei, Hossein
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Fodor, Gabor
    Ericsson Research, Kista, Sweden..
    Modiano, Eytan
    Laboratory for Information and Decision Systems, Massachusetts Institute of Technology, Cambridge, MA 02139 USA..
    Pang, Zhibo
    ABB AB, Corporate Research, 721 78 Västerås, Sweden..
    Zorzi, Michele
    Department of Information Engineering, University of Padova, 35131 Padua, Italy..
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Low-Latency Networking: Where Latency Lurks and How to Tame It2018In: Proceedings of the IEEE, ISSN 0018-9219, E-ISSN 1558-2256, p. 1-27Article in journal (Refereed)
    Abstract [en]

    While the current generation of mobile and fixed communication networks has been standardized for mobile broadband services, the next generation is driven by the vision of the Internet of Things and mission-critical communication services requiring latency in the order of milliseconds or submilliseconds. However, these new stringent requirements have a large technical impact on the design of all layers of the communication protocol stack. The cross-layer interactions are complex due to the multiple design principles and technologies that contribute to the layers' design and fundamental performance limitations. We will be able to develop low-latency networks only if we address the problem of these complex interactions from the new point of view of submilliseconds latency. In this paper, we propose a holistic analysis and classification of the main design principles and enabling technologies that will make it possible to deploy low-latency wireless communication networks. We argue that these design principles and enabling technologies must be carefully orchestrated to meet the stringent requirements and to manage the inherent tradeoffs between low latency and traditional performance metrics. We also review currently ongoing standardization activities in prominent standards associations, and discuss open problems for future research.

  • 115. Kalalas, C.
    et al.
    Gkatzikis, L.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Ljungberg, P.
    Alonso-Zarate, J.
    Enabling IEC 61850 communication services over public LTE infrastructure2016In: 2016 IEEE International Conference on Communications, ICC 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7510937Conference paper (Refereed)
    Abstract [en]

    Ongoing IEC 61850 standardization activities aim at improved grid reliability through advanced monitoring and remote control services in medium- and low-voltage. However, extending energy automation beyond the substation boundaries introduces the need for timely and reliable information exchange over wide areas. LTE appears as a promising solution since it supports extensive coverage, low latency, high throughput and Quality-of-Service (QoS) differentiation. In this paper, the feasibility of implementing IEC 61850 services over public LTE infrastructure is investigated. Since standard LTE cannot meet the stringent latency requirements of such services, a new LTE QoS class is introduced along with a new LTE scheduler that prioritizes automation traffic with respect to background human-centric traffic. Two representative grid automation services are considered, a centralized (MMS) and a distributed one (GOOSE), and the achievable latency/throughput performance is evaluated on a radio system simulator platform. Simulations of realistic overload scenarios demonstrate that properly designed LTE schedulers can successfully meet the performance requirements of IEC 61850 services with negligible impact on background traffic.

  • 116.
    Kant, Shashi
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering. Ericsson AB.
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. Ericsson AB.
    Bengtsson, Mats
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Göransson, Bo
    Ericsson AB.
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Low-Complexity OFDM Spectral Precoding2019In: 20th IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC) 2019, 2019, article id 8815554Conference paper (Refereed)
    Abstract [en]

    This paper proposes a new large-scale mask compliant spectral precoder (LS-MSP) for orthogonal frequency division multiplexing systems. In this paper, we first consider a previously proposed mask-compliant spectral precoding scheme that utilizes a generic convex optimization solver which suffers from high computational complexity, notably in large-scale systems. To mitigate the complexity of computing the LS-MSP, we propose a divide-and-conquer approach that breaks the original problem into smaller rank 1 quadratic-constraint problems and each small problem yields closed-form solution. Based on these solutions, we develop three specialized first-order low-complexity algorithms, based on 1) projection on convex sets and 2) the alternating direction method of multipliers. We also develop an algorithm that capitalizes on the closed-form solutions for the rank 1 quadratic constraints, which is referred to as 3) semianalytical spectral precoding. Numerical results show that the proposed LS-MSP techniques outperform previously proposed techniques in terms of the computational burden while complying with the spectrum mask. The results also indicate that 3) typically needs 3 iterations to achieve similar results as 1) and 2) at the expense of a slightly increased computational complexity.

  • 117.
    Katselis, Dimitrios
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Efficient OOK/DS-CDMA Detection Threshold Selection2013In: 2013 American Control Conference (ACC), American Automatic Control Council , 2013, p. 3523-3528Conference paper (Refereed)
    Abstract [en]

    A major constraint in deployments of wireless sensor networks (WSNs) is the energy consumption related to the battery lifetime of the network nodes. To this end, power efficient digital modulation techniques such as On-Off keying (OOK) are highly attractive. However, the OOK detection thresholds, namely the thresholds against which the received signals are compared to detect which bit is transmitted, must be carefully selected to minimize the bit error rate. This is challenging to accomplish in resource-limited nodes with constrained computational capabilities. In this paper, the system scenario considers simultaneously transmitting nodes in Rayleigh fading conditions. Various iterative algorithms to numerically select the detection thresholds are established. Convergence analysis accompanies these algorithms. Numerical simulations are provided to support the derived results and to compare the proposed algorithms. It is concluded that OOK modulation is beneficial in resource constrained WSNs provided that efficient optimization algorithms are employed for the threshold selection.

  • 118.
    Katselis, Dimitrios
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    OOK/DS-CDMA bit error probability over Rayleigh fading channels2013In: Communications (ICC), 2013 IEEE International Conference on, IEEE conference proceedings, 2013, p. 5619-5624Conference paper (Refereed)
    Abstract [en]

    A major constraint in deployments of resource-limited networks is the energy consumption related to the battery lifetime of the network nodes. To this end, power efficient digital modulation techniques such as On-Off keying (OOK) are highly attractive. In this paper, a novel complete probabilistic description of the Direct Sequence - Coded Division Multiple Access (DS-CDMA) system with random signatures employing OOK modulation is presented. The system scenario considers simultaneously transmitting nodes in Rayleigh fading conditions. Numerical simulations are provided to support the derived results.

  • 119.
    Khaksari, Mohammadreza
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Performance analysis and optimization of the joining protocol for a platoon of vehicles2012In: 5th International Symposium on Communications Control and Signal Processing, ISCCSP 2012, IEEE , 2012, p. 6217873-Conference paper (Refereed)
    Abstract [en]

    Platooning of vehicles allows to saving energy and increasing safety provided that there are reliable wireless communication protocols. In this paper, the optimization of the medium access control (MAC) protocol based on IEEE 802.11e for the platoon joining is investigated. The exchange of prosperous dynamic information among vehicules through certain bounded and closed-fitting timeout windows is challenging. On the one side, safe and secure joining of vehicles to a platoon is time-consuming and in the actual speed of the vehicles may be very difficult. On the other side, the decrease in joining timeout windows results in rising of joining failure. The analytical characterization of the appropriate timeout windows, which is dependent on the rate of exchange messages to request and verify joining, is proposed. By using such a new characterization, the estimation of closed-fitting timeout windows for joining is achieved based on the rate of transferred joining messages. Numerical results show that regular joining timeout windows suffer unacceptable delay for platooning. By contrast, adaptive optimized timeout windows reduce delay of communication. It is concluded that the new optimization proposed in this paper can potentially reduce energy consumption of vehicles and increase safety.

  • 120. Kleinrock, L.
    et al.
    Yang, Z.
    Tan, L.
    Zhuang, W.
    Pan, Y.
    Zukerman, M.
    Lu, C.
    Hiang, C. T.
    Rosberg, Z.
    Li, J.
    Ma, M.
    Yoong, C.
    Hanumanthappa, J.
    Malekian, R.
    Govil, J.
    Abdullah, L. N.
    Sun, H. -M
    Saravanan, V.
    Zafar, N. A.
    Nair, M. S.
    Voyles, R. M.
    Kang, D. -J
    Lee, S. H.
    Fathabadi, H.
    Reza, A. W.
    Samak, A.
    Kenny, R. F.
    Mahmoud, M.
    Algadi, N.
    Laurie, M.
    Mahmoud, S. S.
    Sun, J.
    John, R.
    Niccolo, C.
    Kumar, M. P.
    Chaiwanarom, P.
    Kumar, P. S.
    Marc, S.
    Jilani, T. A.
    Chowdhury, S.
    Ljubo, V.
    Guo, W.
    Mohanty, B. K.
    Ankur, A.
    Sandhu, P. S.
    Hu, W.
    Thatcher, S.
    Srinonchat, J.
    Tabrizi, M. N.
    Ahmed, H. M. S.
    Tobgay, S.
    Sree, P. K.
    Min-Allah, N.
    Alhadidi, B.
    Ahmed, T. O.
    Ménard, P. A.
    Nehra, N. K.
    Chang, C. -Y
    Hung, L. -L
    Fortino, G.
    Wang, C. -L
    Tseng, H. -R
    Orsag, F.
    Calafate, C. T.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Farago, A.
    Pujolle, G.
    Prokhorov, D.
    Busch, C.
    Aravind, A.
    Cuzzocrea, A.
    Bolumar, F. J. S.
    Liu, Y.
    Yang, S.
    Andrew, L.
    Zhang, C.
    Proceedings of the 2010 2nd International Conference on Future Computer and Communication, ICFCC 2010: Preface2010In: Proceedings of the 2010 2nd International Conference on Future Computer and Communication, ICFCC 2010, 2010, p. v-viConference paper (Other academic)
  • 121.
    Lan, Dapeng
    et al.
    Univ Oslo, Dept Informat, N-0316 Oslo, Norway..
    Pang, Zhibo
    ABB Corp Res, S-72226 Vasteras, Sweden..
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Liu, Yu
    Linkoping Univ, Dept Sci & Technol, S-58183 Linkoping, Sweden..
    Taherkordi, Amir
    Univ Oslo, Dept Informat, N-0316 Oslo, Norway..
    Eliassen, Frank
    Univ Oslo, Dept Informat, N-0316 Oslo, Norway..
    Latency Analysis of Wireless Networks for Proximity Services in Smart Home and Building Automation: The Case of Thread2019In: IEEE Access, E-ISSN 2169-3536, Vol. 7, p. 4856-4867Article in journal (Refereed)
    Abstract [en]

    Proximity service (ProSe), using the geographic location and device information by considering the proximity of mobile devices, enriches the services we use to interact with people and things around us. ProSe has been used in mobile social networks in proximity and also in smart home and building automation (Google Home). To enable ProSe in smart home, reliable and stable network protocols and communication infrastructures are needed. Thread is a new wireless protocol aiming at smart home and building automation (BA), which supports mesh networks and native Internet protocol connectivity. The latency of Thread should be carefully studied when used in user-friendly and safety-critical ProSe in smart home and BA. In this paper, a system level model of latency in the Thread mesh network is presented. The accumulated latency consists of different kinds of delay from the application layer to the physical layer. A Markov chain model is used to derive the probability distribution of the medium access control service time. The system level model is experimentally validated in a multi-hop Thread mesh network. The outcomes show that the system model results match well with the experimental results. Finally, based on an analytical model, a software tool is developed to estimate the latency of the Thread mesh network, providing developers more network information to develop user-friendly and safety-critical ProSe in smart home and BA.

  • 122.
    Laoudias, Christos
    et al.
    Huawei Technol, Ireland Res Ctr, Dublin D01 R3K6 1, Ireland.;Univ Cyprus, KIOS Res & Innovat Ctr Excellence, CY-1678 Nicosia, Cyprus..
    Moreira, Adriano
    Univ Minho, Algoritmi Res Ctr, P-4800058 Guimaraes, Portugal..
    Kim, Sunwoo
    Hanyang Univ, Dept Elect Engn, Seoul 04763, South Korea..
    Lee, Sangwoo
    Korea Aerosp Res Inst, Nav Res & Dev Div, Daejeon 34133, South Korea..
    Wirola, Lauri
    HERE, Enterprise Indoor Positioning Solut, Tampere 33100, Finland..
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering. ..
    A Survey of Enabling Technologies for Network Localization, Tracking, and Navigation2018In: IEEE Communications Surveys and Tutorials, ISSN 1553-877X, E-ISSN 1553-877X, Vol. 20, no 4, p. 3607-3644Article in journal (Refereed)
    Abstract [en]

    Location information for events, assets, and individuals, mostly focusing on two dimensions so far, has triggered a multitude of applications across different verticals, such as consumer, networking, industrial, health care, public safety, and emergency response use cases. To fully exploit the potential of location awareness and enable new advanced location-based services, localization algorithms need to be combined with complementary technologies including accurate height estimation, i.e., three dimensional location, reliable user mobility classification, and efficient indoor mapping solutions. This survey provides a comprehensive review of such enabling technologies. In particular, we present cellular localization systems including recent results on 5G localization, and solutions based on wireless local area networks, highlighting those that are capable of computing 3D location in multi-floor indoor environments. We overview range-free localization schemes, which have been traditionally explored in wireless sensor networks and are nowadays gaining attention for several envisioned Internet of Things applications. We also present user mobility estimation techniques, particularly those applicable in cellular networks, that can improve localization and tracking accuracy. Regarding the mapping of physical space inside buildings for aiding tracking and navigation applications, we study recent advances and focus on smartphone-based indoor simultaneous localization and mapping approaches. The survey concludes with service availability and system scalability considerations, as well as security and privacy concerns in location architectures, discusses the technology roadmap, and identifies future research directions.

  • 123. Levorato, M.
    et al.
    Weeraddana, Pradeep Chathuranga
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Distributed optimization of transmission strategies in reactive cognitive networks2014In: 2014 IEEE Global Communications Conference, GLOBECOM 2014, 2014, p. 905-910Conference paper (Refereed)
    Abstract [en]

    A framework for the distributed optimization of reactive cognitive networks with multiple secondary users is presented. The secondary users iteratively locate the policy maximizing their aggregate performance under bounds on the maximum performance loss caused to the primary users. The policy accounts for the impact of interference on the dynamics of the primary users' network due to transmission and channel access protocols. To minimize coordination overhead, it is assumed that the secondary users only coordinate the policy, whereas actions in each slot are independently selected by the individual secondary user based on the agreed policy. The distributed optimization technique proposed herein is based on alternating convex optimization. Numerical results are presented assessing the performance of the obtained transmission policy with respect to the optimal centralized and fully-coordinated policy.

  • 124. Levorato, Marco
    et al.
    Weeraddana, Pradeep Chathuranga
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed Optimization of Channel Access Strategies in Reactive Cognitive Networks2016In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 64, no 10, p. 4121-4133Article in journal (Refereed)
    Abstract [en]

    In reactive cognitive networks, the channel access and the transmission decisions of the cognitive terminals have a long-term effect on the network dynamics. When multiple cognitive terminals coexist, the optimization and implementation of their strategy is challenging and may require considerable coordination overhead. In this paper, such challenge is addressed by a novel framework for the distributed optimization of transmission and channel access strategies. The objective of the cognitive terminals is to find the optimal action distribution depending on the current network state. To reduce the coordination overhead, in the proposed framework the cognitive terminals distributively coordinate the policy, whereas the action in each individual time slot is independently selected by the terminals. The optimization of the transmission and channel access strategy is performed iteratively by using the alternate convex optimization technique, where at each iteration a cognitive terminal is selected to optimize its own action distribution while assuming fixed those of the other cognitive terminals. For a traditional primary-secondary user network configuration, numerical results show that the proposed algorithm converges to a stable solution in a small number of iterations, and a limited performance loss with respect to the perfect coordinated case.

  • 125. Loianno, G.
    et al.
    Lippiello, V.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Siciliano, B.
    Visual and inertial multi-rate data fusion for motion estimation via Pareto-optimization2013In: 2013 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), IEEE , 2013, p. 3993-3999Conference paper (Refereed)
    Abstract [en]

    Motion estimation is an open research field in control and robotic applications. Sensor fusion algorithms are generally used to achieve an accurate estimation of the vehicle motion by combining heterogeneous sensors measurements with different statistical characteristics. In this paper, a new method that combines measurements provided by an inertial sensor and a vision system is presented. Compared to classical modelbased techniques, the method relies on a Pareto optimization that trades off the statistical properties of the measurements. The proposed technique is evaluated with simulations in terms of computational requirements and estimation accuracy with respect to a classical Kalman filter approach. It is shown that the proposed method gives an improved estimation accuracy at the cost of a slightly increased computational complexity.

  • 126. Magnusson, S.
    et al.
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Li, N.
    Optimal voltage control using event triggered communication2019In: e-Energy 2019 - Proceedings of the 10th ACM International Conference on Future Energy Systems, Association for Computing Machinery (ACM), 2019, p. 343-354Conference paper (Refereed)
    Abstract [en]

    The integration of volatile renewable energy into distribution networks on a large scale will demand advanced voltage control algorithms. Communication will be an integral part of these algorithms, however, it is unclear what kind of communication protocols will be most effective for the task. Motivated by such questions, this paper investigates how voltage control can be achieved using event triggered communications. In particular, we consider online algorithms that require the network's buses to communicate only when their voltage is outside a feasible operation range. We prove the convergence of these algorithms to an optimal operating point at the rate O(1/τ), assuming linearized power flows. We illustrate the performance of the algorithms on the full nonlinear AC power flow in simulations. Our results show that event-triggered protocols can significantly reduce the communication for smart grid control.

  • 127.
    Magnusson, Sindri
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering. KTH - Royal Institute of Technology.
    Enyioha, Chinwendu
    Li, Na
    Carlo, Fischione
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Tarokh, Vahid
    Convergence of Limited Communication Gradient Methods2018In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 63, no 5, p. 1356-1371Article in journal (Refereed)
    Abstract [en]

    Distributed optimization increasingly plays a centralrole in economical and sustainable operation of cyber-physicalsystems. Nevertheless, the complete potential of the technologyhas not yet been fully exploited in practice due to communicationlimitations posed by the real-world infrastructures. This workinvestigates fundamental properties of distributed optimizationbased on gradient methods, where gradient information iscommunicated using limited number of bits. In particular, ageneral class of quantized gradient methods are studied wherethe gradient direction is approximated by a finite quantizationset. Sufficient and necessary conditions are provided on sucha quantization set to guarantee that the methods minimize anyconvex objective function with Lipschitz continuous gradient anda nonempty and bounded set of optimizers. A lower bound on thecardinality of the quantization set is provided, along with specificexamples of minimal quantizations. Convergence rate results areestablished that connect the fineness of the quantization andthe number of iterations needed to reach a predefined solutionaccuracy. Generalizations of the results to a relevant class ofconstrained problems using projections are considered. Finally,the results are illustrated by simulations of practical systems.

  • 128.
    Magnusson, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Enyioha, Chinwendu
    Li, Na
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Practical Coding Schemes For Bandwidth Limited One-Way Communication Resource Allocation2016In: 2016 IEEE 55th Conference on Decision and Control, CDC 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 221-226, article id 7798273Conference paper (Refereed)
    Abstract [en]

    This paper investigates resource allocation algorithms that use limited communication - where the supplier of a resource broadcasts a coordinating signal using one bit of information to users per iteration. Rather than relay anticipated consumption to the supplier, the users locally compute their allocation, while the supplier measures the total resource consumption. Since the users do not compare their local consumption against the supplier’s capacity at each iteration, they can easily overload the system and cause an outage (for example blackout in power networks). To address this challenge, this paper investigates pragmatic coding schemes, called PFcodes (Primal-Feasible codes), that not only allow the restriction of communication to a single bit of information, but also avoid system overload due to users’ heavy consumption. We derive a worst case lower bound on the number of bits needed to achieve any desired accuracy using PF-codes. In addition, we demonstrate how to construct time-invariant and time-varying PF-codes. We provide an upper bound on the number of bits needed to achieve any desired solution accuracy using time-invariant PF-codes. Remarkably, the difference between the upper and lower bound is only 2 bits. It is proved that the time-varying PF-codes asymptotically converge to the true primal/dual optimal solution. Simulations demonstrating accuracy of our theoretical analyses are presented.

  • 129.
    Magnusson, Sindri
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Enyioha, Chinwendu
    Harvard Univ, Sch Engn & Appl Sci, Cambridge, MA 02138 USA..
    Li, Na
    Harvard Univ, Sch Engn & Appl Sci, Cambridge, MA 02138 USA..
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Tarokh, Vahid
    Duke Univ, Elect & Comp Engn, Durham, NC 27708 USA..
    Communication Complexity of Dual Decomposition Methods for Distributed Resource Allocation Optimization2018In: IEEE Journal on Selected Topics in Signal Processing, ISSN 1932-4553, E-ISSN 1941-0484, Vol. 12, no 4, p. 717-732Article in journal (Refereed)
    Abstract [en]

    Dual decomposition methods are among the most prominent approaches for finding primal/dual saddle point solutions of resource allocation optimization problems. To deploy these methods in the emerging Internet of things networks, which will often have limited data rates, it is important to understand the communication overhead they require. Motivated by this, we introduce and explore twomeasures of communication complexity of dual decomposition methods to identify the most efficient communication among these algorithms. The first measure is epsilon-complexity, which quantifies the minimal number of bits needed to find an epsilon-accurate solution. The second measure is b-complexity, which quantifies the best possible solution accuracy that can be achieved from communicating b bits. We find the exact epsilon -and b-complexity of a class of resource allocation problems where a single supplier allocates resources to multiple users. For both the primal and dual problems, the epsilon-complexity grows proportionally to log(2) (1/epsilon) and the b-complexity proportionally to 1/2(b). We also introduce a variant of the epsilon- and b-complexity measures where only algorithms that ensure primal feasibility of the iterates are allowed. Such algorithms are often desirable because overuse of the resources can overload the respective systems, e.g., by causing blackouts in power systems. We provide upper and lower bounds on the convergence rate of these primal feasible complexity measures. In particular, we show that the b-complexity cannot converge at a faster rate than O(1/b). Therefore, the results demonstrate a tradeoff between fast convergence and primal feasibility. We illustrate the result by numerical studies.

  • 130.
    Magnusson, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Heal, Kathryn
    Enyioha, Chinwendu
    Li, Na
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Convergence of Limited Communications Gradient Methods2016In: 2016 American Control Conference (ACC), IEEE, 2016, p. 1421-1426Conference paper (Refereed)
    Abstract [en]

    Distributed control and decision making increasingly play a central role in economical and sustainable operation of cyber-physical systems. Nevertheless, the full potential of the technology has not yet been fully exploited in practice due to communication limitations of real-world infrastructures. This work investigates the fundamental properties of gradient methods for distributed optimization, where gradient information is communicated at every iteration, when using limited number of communicated bits. In particular, a general class of quantized gradient methods are studied where the gradient direction is approximated by a finite quantization set. Conditions on the quantization set are provided that are necessary and sufficient to guarantee the ability of these methods to minimize any convex objective function with Lipschitz continuous gradient and a nonempty, bounded set of optimizers. Moreover, a lower bound on the cardinality of the quantization set is provided, along with specific examples of minimal quantizations. Furthermore, convergence rate results are established that connect the fineness of the quantization and number of iterations needed to reach a predefined solution accuracy. The results provide a bound on the number of bits needed to achieve the desired accuracy. Finally, an application of the theory to resource allocation in power networks is demonstrated, and the theoretical results are substantiated by numerical simulations.

  • 131.
    Magnusson, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Heal, Kathryn
    Enyioha, Chinwendu
    Li, Na
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Tarokh, Vahie
    Convergence of Limited Communications Gradient MethodsManuscript (preprint) (Other academic)
  • 132.
    Magnusson, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Heal, Kathryn
    Enyioha, Chinwendu
    Li, Na
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Tarokh, Vahie
    Distributed Resource Allocation Using One-Way Communication with Applications to Power NetworksManuscript (preprint) (Other academic)
    Abstract [en]

    Nonconvex and structured optimization problemsarise in many engineering applications that demand scalableand distributed solution methods. The study of the convergenceproperties of these methods is in general difficult due to thenonconvexity of the problem. In this paper, two distributedsolution methods that combine the fast convergence propertiesof augmented Lagrangian-based methods with the separabilityproperties of alternating optimization are investigated. The firstmethod is adapted from the classic quadratic penalty functionmethod and is called the Alternating Direction Penalty Method(ADPM). Unlike the original quadratic penalty function method,in which single-step optimizations are adopted, ADPM uses analternating optimization, which in turn makes it scalable. Thesecond method is the well-known Alternating Direction Methodof Multipliers (ADMM). It is shown that ADPM for nonconvexproblems asymptotically converges to a primal feasible pointunder mild conditions and an additional condition ensuringthat it asymptotically reaches the standard first order necessary conditions for local optimality are introduced. In thecase of the ADMM, novel sufficient conditions under whichthe algorithm asymptotically reaches the standard first ordernecessary conditions are established. Based on this, completeconvergence of ADMM for a class of low dimensional problemsare characterized. Finally, the results are illustrated by applyingADPM and ADMM to a nonconvex localization problem inwireless sensor networks.

  • 133.
    Magnusson, Sindri
    et al.
    Harvard Univ, Sch Engn & Appl Sci, Cambridge, MA 02138 USA..
    Qu, Guannan
    Harvard Univ, Sch Engn & Appl Sci, Cambridge, MA 02138 USA..
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Li, Na
    Harvard Univ, Sch Engn & Appl Sci, Cambridge, MA 02138 USA..
    Voltage Control Using Limited Communication2019In: IEEE Transactions on Big Data, ISSN 2325-5870, E-ISSN 2168-6750, Vol. 6, no 3, p. 993-1003Article in journal (Refereed)
    Abstract [en]

    In electricity distribution networks, the increasing penetration of renewable energy generation necessitates faster and more sophisticated voltage controls. Unfortunately, recent research shows that local voltage control fails in achieving the desired regulation, unless there is communication between the controllers. However, the communication infrastructure for distribution systems is less reliable and less ubiquitous compared to that for the bulk transmission system. In this paper, we design distributed voltage control that uses limited communication. That is, only neighboring buses need to communicate a few bits between each other for each control step. We investigate how these controllers can achieve the desired asymptotic behavior of the voltage regulation and we provide upper bounds on the number of bits that are needed to ensure a predefined accuracy of the regulation. Finally, we illustrate the results by numerical simulations.

  • 134.
    Magnusson, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Weeraddana, Pradeep Chathuranga
    Rabbat, Michael
    McGill University.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    On the Convergence of Alternating Direction Lagrangian Methods for Nonconvex Structured Optimization Problems2015In: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 3, no 3, p. 296-309, article id 7239586Article in journal (Refereed)
    Abstract [en]

    Nonconvex and structured optimization problemsarise in many engineering applications that demand scalableand distributed solution methods. The study of the convergenceproperties of these methods is in general difficult due to thenonconvexity of the problem. In this paper, two distributedsolution methods that combine the fast convergence propertiesof augmented Lagrangian-based methods with the separabilityproperties of alternating optimization are investigated. The firstmethod is adapted from the classic quadratic penalty functionmethod and is called the Alternating Direction Penalty Method(ADPM). Unlike the original quadratic penalty function method,in which single-step optimizations are adopted, ADPM uses analternating optimization, which in turn makes it scalable. Thesecond method is the well-known Alternating Direction Methodof Multipliers (ADMM). It is shown that ADPM for nonconvexproblems asymptotically converges to a primal feasible pointunder mild conditions and an additional condition ensuringthat it asymptotically reaches the standard first order necessary conditions for local optimality are introduced. In thecase of the ADMM, novel sufficient conditions under whichthe algorithm asymptotically reaches the standard first ordernecessary conditions are established. Based on this, completeconvergence of ADMM for a class of low dimensional problemsare characterized. Finally, the results are illustrated by applyingADPM and ADMM to a nonconvex localization problem inwireless sensor networks.

  • 135.
    Magnússon, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Chathuranga Weeraddana, Pradeep
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A Distributed Approach for the Optimal Power Flow Problem Based on ADMM and Sequential Convex Approximations2015In: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 2, no 3, p. 238-253Article in journal (Refereed)
    Abstract [en]

    The optimal power flow (OPF) problem, which playsa central role in operating electrical networks is considered. Theproblem is nonconvex and is in fact NP hard. Therefore, designingefficient algorithms of practical relevance is crucial, thoughtheir global optimality is not guaranteed. Existing semi-definiteprogramming relaxation based approaches are restricted to OPFproblems where zero duality holds. In this paper, an efficientnovel method to address the general nonconvex OPF problemis investigated. The proposed method is based on alternatingdirection method of multipliers combined with sequential convexapproximations. The global OPF problem is decomposed intosmaller problems associated to each bus of the network, thesolutions of which are coordinated via a light communicationprotocol. Therefore, the proposed method is highly scalable. Theconvergence properties of the proposed algorithm are mathematicallysubstantiated. Finally, the proposed algorithm is evaluatedon a number of test examples, where the convergence propertiesof the proposed algorithm are numerically substantiated and theperformance is compared with a global optimal method.

  • 136.
    Magnússon, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Chinwendu, Enyioha
    Li, Na
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Tarokh, Vahid
    Communication Complexity of Resource Allocation OptimizationManuscript (preprint) (Other academic)
  • 137.
    Magnússon, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Enyioha, Chinwendu
    Harvard University.
    Hea, Kathryn
    Li, Na
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Tarokh, Vahid
    Distributed Resource Allocation Using One-Way Communication with Applications to Power Networks2016In: 2016 50th Annual Conference on Information Systems and Sciences, CISS 2016, IEEE conference proceedings, 2016, p. 631-636, article id 7460576Conference paper (Refereed)
    Abstract [en]

    Typical coordination schemes for future powergrids require two-way communications. Since the number of end power-consuming devices is large, the bandwidth requirements for such two-way communication schemes may be prohibitive. Motivated by this observation, we study distributed coordination schemes that require only one-way limited communications. In particular, we investigate how dual descent distributed optimization algorithm can be employed in power networks using one-way communication. In this iterative algorithm, system coordinators broadcast coordinating (or pricing) signals to the users/devices who update power consumption based on the received signal. Then system coordinators update the coordinating signals based on the physical measurement of the aggregate power usage. We provide conditions to guarantee the feasibility of the aggregated power usage at each iteration so as to avoid blackout. Furthermore, we prove the convergence of algorithms under these conditions, and establish its rate of convergence. We illustrate the performance of our algorithms using numerical simulations. These results show that one-way limited communication may be viable for coordinating/operating the future smart grids.

  • 138.
    Magnússon, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Enyioha, Chinwendu
    Li, Na
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Tarokh, Vahid
    Convergence of Limited Communications Gradient MethodsArticle in journal (Other academic)
    Abstract [en]

    Distributed optimization increasingly plays a centralrole in economical and sustainable operation of cyber-physicalsystems. Nevertheless, the complete potential of the technologyhas not yet been fully exploited in practice due to communicationlimitations posed by the real-world infrastructures. This workinvestigates fundamental properties of distributed optimizationbased on gradient methods, where gradient information iscommunicated using limited number of bits. In particular, ageneral class of quantized gradient methods are studied wherethe gradient direction is approximated by a finite quantizationset. Sufficient and necessary conditions are provided on sucha quantization set to guarantee that the methods minimize anyconvex objective function with Lipschitz continuous gradient anda nonempty and bounded set of optimizers. A lower bound on thecardinality of the quantization set is provided, along with specificexamples of minimal quantizations. Convergence rate results areestablished that connect the fineness of the quantization andthe number of iterations needed to reach a predefined solutionaccuracy. Generalizations of the results to a relevant class ofconstrained problems using projections are considered. Finally,the results are illustrated by simulations of practical systems.

  • 139.
    Magnússon, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Li, N.
    Voltage Control Using Limited Communication2017In: IFAC-PapersOnLine, ISSN 2405-8963, Vol. 50, no 1, p. 1-6Article in journal (Refereed)
    Abstract [en]

    In electricity distribution networks, the increasing penetration of renewable energy generation necessitates faster and more sophisticated voltage controls. Unfortunately, recent research shows that local voltage control fails in achieving the desired regulation, unless there is some communication between the controllers. However, the communication infrastructure for distribution systems are less reliable and less ubiquitous as compared to that for the bulk transmission system. In this paper, we design distributed voltage control that use limited communication. That is, only neighboring buses need to communicate few bits between each other before each control step. We investigate how these controllers can achieve the desired asymptotic behavior of the voltage regulation and we provide upper bounds on the number of bits that are needed to ensure a predefined accuracy of the regulation. Finally, we illustrate the results by numerical simulations.

  • 140.
    Magnússon, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jakobsson, Martin
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Weeraddana, Pradeep Chathuranga
    On some extensions of Fast-Lipschitz optimization2016In: 2016 European Control Conference (ECC), IEEE, 2016, p. 172-177, article id 7810282Conference paper (Refereed)
    Abstract [en]

    The need of fast distributed solvers for optimization problems in networked systems has motivated the recent development of the Fast-Lipschitz optimization framework. In such an optimization, problems satisfying certain qualifying conditions, such as monotonicity of the objective function and contractivity of the constraints, have a unique optimal solution obtained via fast distributed algorithms that compute the fixed point of the constraints. This paper extends the set of problems for which the Fast-Lipschitz framework applies. Existing assumptions on the problem form are relaxed and new qualifying conditions are established. It is shown for which cases of more constraints than decision variables, and less constraints than decision variables Fast-Lipschitz optimization applies. New results are obtained by imposing non strict monotonicity of the objective functions. The extended Fast-Lipschitz framework is illustrated by a number of examples, including network optimization and optimal control problems

  • 141.
    Magnússon, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Li, Na
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Voltage Control Using Limited CommunicationManuscript (preprint) (Other academic)
  • 142.
    Magnússon, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Weeraddana, Pradeep Chathuranga
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A distributed approach for the optimal power flow problem2016In: 2016 European Control Conference (ECC), Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 1940-1945, article id 7810575Conference paper (Refereed)
    Abstract [en]

    For operating electrical power networks, the Optimal Power Flow (OPF) problem plays a central role. The problem is nonconvex and NP hard. Therefore, designing efficient solution algorithms is crucial, though their global optimality is not guaranteed. Existing semi-definite programming relaxation based approaches are restricted to OPF problems for which zero duality holds, whereas for non-convex problems there is a lack of solution methods of provable performance. In this paper, an efficient novel method to address the general nonconvex OPF problem is investigated. The proposed method is based on alternating direction method of multipliers combined with sequential convex approximations. The global OPF problem is decomposed into smaller problems associated to each bus of the network, the solutions of which are coordinated via a light communication protocol. Therefore, the proposed method is highly scalable. The convergence properties of the proposed algorithm are mathematically and numerically substantiated.

  • 143.
    Magnússon, Sindri
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Weeraddana, Pradeep Chathuranga
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Rabbat, Michael
    McGill University, Department of Electrical and Computer Engineering.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    On the Convergence of an Alternating Direction Penalty Method for Nonconvex Problems2015In: Signals, Systems and Computers, 2015 Asilomar Conference on, IEEE Computer Society, 2015Conference paper (Other academic)
    Abstract [en]

    This paper investigates convergence properties ofscalable algorithms for nonconvex and structured optimization.We consider a method that is adapted from the classic quadraticpenalty function method, the Alternating Direction PenaltyMethod (ADPM). Unlike the original quadratic penalty functionmethod, in which single-step optimizations are adopted, ADPMuses alternating optimization, which in turn is exploited toenable scalability of the algorithm. A special case of ADPM isa variant of the well known Alternating Direction Method ofMultipliers (ADMM), where the penalty parameter is increasedto infinity. We show that due to the increasing penalty, theADPM asymptotically reaches a primal feasible point undermild conditions. Moreover, we give numerical evidence thatdemonstrates the potential of the ADPM for computing localoptimal points when the penalty is not updated too aggressively.

  • 144.
    Mazhar, Othmane
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Rojas, Cristian R.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Bayesian model selection for change point detection and clustering2018In: 35th International Conference on Machine Learning, ICML 2018, International Machine Learning Society (IMLS) , 2018, p. 5497-5520Conference paper (Refereed)
    Abstract [en]

    We address a generalization of change point detection with the purpose of detecting the change locations and the levels of clusters of a piece- wise constant signal. Our approach is to model it as a nonparametric penalized least square model selection on a family of models indexed over the collection of partitions of the design points and propose a computationally efficient algorithm to approximately solve it. Statistically, minimizing such a penalized criterion yields an approximation to the maximum a-posteriori probability (MAP) estimator. The criterion is then ana-lyzed and an oracle inequality is derived using a Gaussian concentration inequality. The oracle inequality is used to derive on one hand conditions for consistency and on the other hand an adaptive upper bound on the expected square risk of the estimator, which statistically motivates our approximation. Finally, we apply our algorithm to simulated data to experimentally validate the statistical guarantees and illustrate its behavior.

  • 145.
    Mekikis, Prodromos Vasileios
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Athanasiou, Georgios
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    A wireless sensor network testbed for event detection in smart homes2013In: 2013 9th IEEE International Conference On Distributed Computing In Sensor Systems (IEEE DCOSS 2013), IEEE Computer Society, 2013, p. 321-322Conference paper (Refereed)
    Abstract [en]

    In smart homes, it is essential to reliably detect events including water leakages. A control action, such as shutting the water pipes, relies on reliable event detection. In this demo, a wireless sensor network for detection and localization of events in smart homes is presented. The demo is based on novel distributed detection-estimation and localization algorithms. A graphical user interface to visualize in real-time the network status is developed. Upon a detected event, the user is alerted through a Twitter notification. In the experiments the false alarm probability is improved by 30% and the average relative localization error is 1.7%.

  • 146. Millán, P.
    et al.
    Vivas, C.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed event-based observers for LTI systems2015In: Asynchronous Control for Networked Systems, Springer Publishing Company, 2015, p. 181-191Chapter in book (Other academic)
    Abstract [en]

    This chapter is concerned with the networked distributed estimation problem. A set of agents (observers) are assumed to be estimating the state of a large-scale process. Each of them must provide a reliable estimate of the state of the plant, but it have only access to some plant outputs. Local observability is not assumed, so the agents need to communicate and collaborate to obtain their estimates. This chapter proposes a structure of the observers, which merges local Luenberger-like estimators with consensus matrices.

  • 147.
    Moghadam, Nima N.
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Shokri-Ghadikolaei, Hossein
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Pilot precoding and combining in multiuser MIMO networks2017In: 2017 IEEE International Conference on Acoustics Speech and Signal Processing ICASSP (ICASSP), Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 3544-3548Conference paper (Refereed)
    Abstract [en]

    Although the benefits of precoding and combining of data streams are widely recognized, the potential of precoding the pilot signals at the user equipment (UE) side and combining them at the base station (BS) side has not received adequate attention. This paper considers a multiuser multiple input multiple output (MU-MIMO) cellular system in which the BS acquires channel state information (CSI) by means of uplink pilot signals and proposes pilot precoding and combining to improve the CSI quality. We first evaluate the channel estimation performance of a baseline scenario in which CSI is acquired with no pilot precoding. Next, we characterize the channel estimation error when the pilot signals are precoded by spatial filters that asymptotically maximize the channel estimation quality. Finally, we study the case when, in addition to pilot precoding at the UE side, the BS utilizes the second order statistics of the channels to further improve the channel estimation performance. The analytical and numerical results show that, specially in scenarios with large number of antennas at the BS and UEs, pilot precoding and combining has a great potential to improve the channel estimation quality in MU-MIMO systems.

  • 148. Möller, N.
    et al.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Santucci, F.
    Graziosi, F.
    Modelling and control of IP transport in cellular radio links,2005Conference paper (Refereed)
    Abstract [en]

    A fundamental assumption of the TCP protocol is that packet losses indicate congestion on the network. This is a problem when using TCP over wireless links, because a noisy radio transmission may erroneously indicate congestion and thereby reduce the TCP sending rate. Two partial solutions, which improve the quality of the radio link, are power control and link-layer retransmissions. We consider a radio channel with multiple users and traffic classes, and investigate how parameters in the radio model influences TCP-related quality measures, such as the average delay and the probability of spurious timeout. The results indicate that the outer loop power control is robust to uncertainties in the radio model. This robustness property supports separation between the radio layer design and the ip and TCP layers.

  • 149.
    Möller, Niels
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Arvidsson, Åke
    Petersson, Justus
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skog, Robert
    Karlsson, Patrik
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Supporting end-to-end applications over HSDPA by cross-layer signalling2007In: IEEE WIRELESS COMMUNICATIONS & NETWORKING CONFERENCE, VOLS 1-9, NEW YORK: IEEE , 2007, p. 3858-3863Conference paper (Refereed)
    Abstract [en]

    A new control structure is proposed to improve user experience of wireless Internet. Information on radio bandwidth and queue length available in the radio network, close to the base station, is used in a proxy that resides between the Internet and the cellular system. The control algorithm in the proxy sets the window size according to event-triggered information on radio bandwidth changes and time-triggered information on the queue length at the wireless link. The mechanism is compared to TCP Reno in two simulation scenarios. The first scenario models a dedicated channel with stepwise changes in the bandwidth, while the second scenario models the High-speed Downlink Shared Channel recently introduced by 3GPP. The proposed mechanism significantly reduces the amount of buffer space needed in the radio network, and it also gives modest improvements to user response time and link utilization. Reduced buffering is particularly beneficial for third-party end-to-end real-time services such as voice, video, and online gaming.

  • 150.
    Najari Moghadam, Nima
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Shokri-Ghadikolaei, Hossein
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Pilot Precoding and Combining in Multiuser MIMO Networks2017In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. June, no 6Article in journal (Refereed)
    Abstract [en]

    Although the benefits of precoding and combining data signals are widely recognized, the potential of these techniques for pilot transmission is not fully understood. This is particularly relevant for multiuser multiple-input multiple-output(MU-MIMO) cellular systems using millimeter-wave (mmWave)communications, where multiple antennas have to be used both at the transmitter and the receiver to overcome the severe path loss.In this paper, we characterize the gains of pilot precoding and combining in terms of channel estimation quality and achievable data rate. Specifically, we consider three uplink pilot transmission scenarios in a mmWave MU-MIMO cellular system: 1) non-precoded and uncombined, 2) precoded but uncombined, and3) precoded and combined. We show that a simple precoder that utilizes only the second-order statistics of the channel reduces the variance of the channel estimation error by a factor that is proportional to the number of user equipment (UE) antennas.We also show that using a linear combiner design based on the second-order statistics of the channel significantly reduces multiuser interference and provides the possibility of reusing some pilots. Specifically, in the large antenna regime, pilot preceding and combining help to accommodate a large number ofUEs in one cell, significantly improve channel estimation quality, boost the signal-to-noise ratio of the UEs located close to the cell edges, alleviate pilot contamination, and address the imbalanced coverage of pilot and data signals.

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