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  • 1.
    António, Gonga
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Landsiedel, O.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Multi-channel communication vs. adaptive routing for reliable communication in WSNs2012In: IPSN'12 - Proceedings of the 11th International Conference on Information Processing in Sensor Networks, Association for Computing Machinery (ACM), 2012, p. 125-126Conference paper (Refereed)
    Abstract [en]

    Interference and link dynamics constitute great concerns for stability and performance of protocols in WSNs. In this paper we evaluate the impact of channel hopping and adaptive routing on delay and reliability focusing on delay critical applications.

  • 2. Belleschi, Marco
    et al.
    Balucanti, Lapo
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Abrardo, Andrea
    Fast power control for cross-layer optimal resource allocation in DS-CDMA wireless networks2009In: 2009 IEEE International Conference on Communications, 2009, p. 4341-4346Conference paper (Refereed)
    Abstract [en]

    This paper presents a novel cross-layer design for joint power and end-to-end rate control optimization in DS-CDMA wireless networks, along with a detailed implementation and evaluation in the network simulator ns-2. Starting with a network utility maximization formulation of the problem, we derive distributed power control, transport rate and queue management schemes that jointly achieve 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, and uses simplified power control mechanisms with reduced signalling requirements. We argue that these features are critical for a successful real-world implementation. To validate these claims, we present a detailed implementation of a crosslayer adapted networking stack for DS-CSMA ad-hoc networks in ns-2. We describe several critical issues that arise in the implementation, but are typically neglected in the theoretical protocol design, and evaluate the alternatives in extensive simulations.

  • 3.
    Demirel, Burak
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Zou, Zhenhua
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Modular Co-Design of Controllers and Transmission Schedules in WirelessHART2011In: IEEE Conference on Decision and Control, 2011, p. 5951-5958Conference paper (Refereed)
    Abstract [en]

    We consider the joint design of transmissionschedules and controllers for networked control loops that useWirelessHART communication for sensor and actuator data. Byparameterizing the design problem in terms of the samplingrate of the control loop, the co-design problem separates intotwo well-defined subproblems which admit optimal solutions:transmission scheduling should be done to maximize the delayconstrained reliability while the control design should optimizeclosed-loop performance under packet loss. We illustrate howthese problems can be solved and demonstrate our co-designframework for the case of linear-quadratic contro

  • 4.
    Demirel, Burak
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zou, Zhenhua
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Soldati, Pablo
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Modular Design of Jointly Optimal Controllers and Forwarding Policies for Wireless Control2014In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 59, no 12, p. 3252-3265Article in journal (Refereed)
    Abstract [en]

    We consider the joint design of packet forwarding policies and controllers for wireless control loops where sensor measurements are sent to the controller over an unreliable and energy-constrained multi-hop wireless network. For fixed sampling rate of the sensor, the co-design problem separates into two well-defined and independent subproblems: transmission scheduling for maximizing the deadline-constrained reliability and optimal control under packet loss. We develop optimal and implementable solutions for these subproblems and show that the optimally co-designed system can be efficiently found. Numerical examples highlight the many trade-offs involved and demonstrate the power of our approach.

  • 5.
    Fodor, Gabor
    et al.
    Ericsson Research, Sweden.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Near optimum power control and precoding under fairness constraints in network MIMO systems2009In: International Journal of Digital Multimedia Broadcasting, ISSN 1687-7578, Vol. 2010, p. 251719-Article in journal (Refereed)
    Abstract [en]

    We consider the problem of setting the uplink signal-to-noise-and- interference (SINR) target and allocating transmit powers for mobile stations in multicell spatial multiplexing wireless systems. Our aim is twofold: to evaluate the potential of such mechanisms in network multiple input multiple output (MIMO) systems, and to develop scalable numerical schemes that allow real-time near-optimal resource allocation across multiple sites. We formulate two versions of the SINR target and power allocation problem: one for maximizing the sum rate subject to power constraints, and one for minimizing the total power needed to meet a sum-rate target. To evaluate the potential of our approach, we perform a semianalytical study in Mathematica using the augmented Lagrangian penalty function method. We find that the gain of the joint optimum SINR setting and power allocation may be significant depending on the degree of fairness that we impose. We develop a numerical technique, based on successive convexification, for real-time optimization of SINR targets and transmit powers. We benchmark our procedure against the globally optimal solution and demonstrate consistently strong performance in realistic network MIMO scenarios. Finally, we study the impact of near optimal precoding in a multicell MIMO environment and find that precoding helps to reduce the sum transmit power while meeting a capacity target.

  • 6. Fodor, Gabor
    et al.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Near Optimum Power Control Under Fairness Constraints in CoMP Systems2009In: GLOBECOM 2009 - 2009 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, 2009, p. 5274-5281Conference paper (Refereed)
    Abstract [en]

    We consider the problem of setting the uplink signal-to-noise-and-interference (SINR) target and allocating transmit powers for mobile stations in multicell spatial multiplexing wireless systems. Our aim is twofold: to evaluate the potential of such mechanisms in coordinated multipoint transmission (CoMP) systems, and to develop scalable numerical schemes that allow real-time near-optimal resource allocation across multiple sites. We formulate two versions of the SINR target and power allocation problem: one for maximizing the sum rate subject to power constraints, and one for minimizing the total power needed to meet a sum-rate target. To evaluate the potential of our approach, we perform a semi-analytical study in Mathematica using the augmented Lagrangian penalty function method. We find that the gain of the joint optimum SINR setting and power allocation may be significant depending on the degree of fairness that we impose. We develop a numerical technique, based on successive convexification, for real-time optimization of SINR targets and transmit powers. We benchmark our procedure against the globally optimal solution, and demonstrate consistently strong performance in realistic CoMP scenarios.

  • 7.
    Fodor, Gabor
    et al.
    Ericsson Research, Sweden.
    Sorrentino, Stefano
    Ericsson Research, Sweden.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On the impact of uplink power control in network MIMO systems with MMSE and SIC receivers2010In: 2010 IEEE International Symposium on 'A World of Wireless, Mobile and Multimedia Networks', 2010, Vol. WoWMoM 2010 - Digital ProceedingsConference paper (Refereed)
    Abstract [en]

    Network multiple input, multiple output (MIMO) systems are built around a broadband backbone network that allows for the fast communication of channel state information (CSI) as well as user data between different base stations. Previous works have shown that multicell channel adaptive (opportunistic) power control can minimize the sum power or maximize the sum rate when the backbone is used for the exchange of CSI in network MIMO systems. In this work we investigate the gains of multicell opportunistic power control under per user fairness constraints when both CSI and user data are shared between multiple sites. We find that multicell opportunistic power control working in concert with uplink joint signal detection is an efficient means both for the capacity and the power control problems that not only minimizes sum power or maximizes overall capacity, but is also able to provide arbitrary level of fairness.

  • 8.
    Ghadimi, Euhanna
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Landsiedel, O.
    Soldati, Pablo
    Huawei Technologies Sweden AB, Sweden.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    A metric for opportunistic routing in duty cycled wireless sensor networks2012In: Sensor, Mesh and Ad Hoc Communications and Networks (SECON), 2012 9th Annual IEEE Communications Society Conference on, IEEE , 2012, p. 335-343Conference paper (Refereed)
    Abstract [en]

    Opportunistic routing is widely known to have substantially better performance than traditional unicast routing in wireless networks with lossy links. However, wireless sensor networks are heavily duty-cycled, i.e. they frequently enter deep sleep states to ensure long network life-time. This renders existing opportunistic routing schemes impractical, as they assume that nodes are always awake and can overhear other transmissions. In this paper, we introduce a novel opportunistic routing metric that takes duty cycling into account. By analytical performance modeling and simulations, we show that our routing scheme results in significantly reduced delay and improved energy efficiency compared to traditional unicast routing. The method is based on a new metric, EDC, that reflects the expected number of duty cycled wakeups that are required to successfully deliver a packet from source to destination. We devise distributed algorithms that find the EDC-optimal forwarding, i.e. the optimal subset of neighbors that each node should permit to forward its packets. We compare the performance of the new routing with ETX-optimal single path routing in both simulations and testbed-based experiments.

  • 9.
    Ghadimi, Euhanna
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Landsiedel, Olaf
    Department of Computer Science and Engineering, Chalmers University of Technology, Sweden .
    Soldati, Pablo
    Huawei Technologies Sweden AB, Sweden.
    Duquennoy, Simon
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Opportunistic routing in low duty-cycle wireless sensor networks2014In: ACM transactions on sensor networks, ISSN 1550-4867, E-ISSN 1550-4859, Vol. 10, no 4, p. 67-Article in journal (Refereed)
    Abstract [en]

    Opportunistic routing is widely known to have substantially better performance than unicast routing in wireless networks with lossy links. However, wireless sensor networks are usually duty cycled, that is, they frequently enter sleep states to ensure long network lifetime. This renders existing opportunistic routing schemes impractical, as they assume that nodes are always awake and can overhear other transmissions. In this article we introduce ORW, a practical opportunistic routing scheme for wireless sensor networks. ORW uses a novel opportunistic routing metric, EDC, that reflects the expected number of duty-cycled wakeups that are required to successfully deliver a packet from source to destination. We devise distributed algorithms that find the EDC-optimal forwarding and demonstrate using analytical performance models and simulations that EDC-based opportunistic routing results in significantly reduced delay and improved energy efficiency compared to traditional unicast routing. In addition, we evaluate the performance of ORW in both simulations and testbed-based experiments. Our results show that ORW reduces radio duty cycles on average by 50% (up to 90% on individual nodes) and delays by 30% to 90% when compared to the state-of-the-art.

  • 10.
    Ghadimi, Euhanna
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Österlind, F.
    Zhang, Haibo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Hidden Terminal-Aware Contention Resolution With an Optimal Distribution2011In: Proceedings - 8th IEEE International Conference on Mobile Ad-hoc and Sensor Systems, MASS 2011, 2011, p. 182-191Conference paper (Refereed)
    Abstract [en]

    Achieving low-power operation in wireless sensor networks with high data load or bursty traffic is challenging. The hidden terminal problem is aggravated with increased amounts of data in which traditional backoff-based contention resolution mechanisms fail or induce high latency and energy costs. We analyze and optimize Strawman, a receiver-initiated contention resolution mechanism that copes with hidden terminals. We propose new techniques to boost the performance of Strawman while keeping the resolution overhead small. We finally validate our improved mechanism via experiments.

  • 11.
    Loretti, Simone
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Cross-layer optimization of multi-hop radio networks with multi-user detectors2005In: IEEE Wireless Communications and Networking Conference, WCNC, 2005, p. 2201-2206Conference paper (Refereed)
    Abstract [en]

    We present an efficient approach for crosslayer optimization of a class of wireless networks equipped with multi-user detectors. For a given network, the method provides the optimal operation of transport, routing and radio link layers as well as the optimal coordination across the layers. The algorithm combines a column generation procedure with an optimal greedy resource allocation scheme into a powerful numerical method for computing the performance limits for networks of significant sizes. The method is applied to a simple network scenario and performance benefits of multi-user detectors and cross-layer coordination over alternative schemes are investigated.

  • 12.
    Park, Pan Gun
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Di Marco, Piergiuseppe
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Soldati, Pablo
    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.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A generalized Markov chain model for effective analysis of slotted IEEE 802.15.42009In: 2009 IEEE 6th International Conference on Mobile Adhoc and Sensor Systems, 2009, Vol. MASS '09, p. 130-139Conference paper (Refereed)
    Abstract [en]

    A generalized analysis of the IEEE 802.15.4 medium access control (MAC) protocol in terms of reliability, delay and energy consumption is presented. The IEEE 802.15.4 exponential backoff process is modeled through a Markov chain taking into account retry limits, acknowledgements, and unsaturated traffic. Simple and effective approximations of the reliability, delay and energy consumption under low traffic regime are proposed. It is demonstrated that the delay distribution of IEEE 802.15.4 depends mainly on MAC parameters and collision probability. In addition, the impact of MAC parameters on the performance metrics is analyzed. The analysis is more general and gives more accurate results than existing methods in the literature. Monte Carlo simulations confirm that the proposed approximations offer a satisfactory accuracy.

  • 13.
    Pesonen, Joonas
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Zhang, Haibo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Methodology and tools for controller-networking codesign in WirelessHART2009In: ETFA 2009 - 2009 IEEE Conference on Emerging Technologies and Factory Automation, IEEE conference proceedings, 2009Conference paper (Refereed)
    Abstract [en]

    This paper describes a methodology for controller and communication scheduling co-design in control systems operating over wirelessHART networks. Data collection and dissemination operations are identified and scheduled to minimize the nominal communication latency. Techniques for improving the reliability of the network when link transmissions are unreliable are discussed, and a Markov-chain model for computing the latency distribution of data collection operations for a given schedule is proposed. The resulting latency models allow to represent the networked control loop as a jump-linear system, whose performance can be analyzed using techniques from stochastic control. We demonstrate how this framework can be used to co-design a networked LQG controller for a five-by-five MIMO control loop.

  • 14.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES).
    Cross-layer optimization of wireless multi-hop networks2007Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    The interest in wireless communications has grown constantly for the past decades, leading to an enormous number of applications and services embraced by billions of users. In order to meet the increasing demand for mobile Internet access, several high data-rate radio networking technologies have been proposed to offer wide area high-speed wireless communications, eventually replacing fixed (wired) networks for many applications.

    This thesis considers cross-layer optimization of multi-hop radio networks where the system performance can be improved if the traditionally separated network layers are jointly optimized. The networks we consider have links with variable transmission rates, influenced by the allocation of transmission opportunities and channels, modulation and coding schemes and transmit powers. First, we formulate the optimal network operation as the solution to a network utility maximization problem and review decomposition methods from mathematical programming that allow translating a centralized network optimization problem into distributed mechanisms and protocols. Second, particular focus is given to networks employing spatial-reuse TDMA, where we develop detailed distributed solutions for joint end-to-end communication rate selection, multiple time-slot transmission scheduling and power allocation which achieve the optimal network utility. In the process, we introduce a novel decomposition method for convex optimization, establish its convergence 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 distributed maximization of computing the schedule updates (maximizing congestion-weighted throughput) and suggest two schemes for distributed channel reservation and power control under realistic interference models. Third, investigate the advantages of employing multi-user detectors within a CDMA/TDMA framework. We demonstrate how column generation techniques can be combined with resource allocation schemes for the multi-access channel into a very efficient computational method. Fourth, we investigate the benefits and challenges of using the emerging OFDMA modulation scheme within our framework. Specifically, we consider the problem of assigning sub-carriers to wireless links in multi-hop mesh networks. Since the underlying mathematical programming problem is computationally hard, we develop a specialized algorithm that computes optimal near-optimal solutions in a reasonable time and suggest a heuristic for improving computation at the price of relatively modest performance losses.

  • 15.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    On Cross-Layer Design and Resource Scheduling in Wireless Networks2009Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Wireless technology has revolutionized the world of communications, enabling ubiquitous connectivity and leading every year to several new applications and services embraced by billions of users. To meet the increasing demand for high data-rate wireless services, standardization bodies and vendors released a new generation of standard-based devices capable to offer wide area high-speed and high-quality wireless coverage. More recently, wireless sensor networks (WSNs) have captured the attention of the industry society to migrate substantial parts of the traditionally wired industrial infrastructure to wireless technologies. Despite the increasing appetite for wireless services, the basic physical resource of these systems, the bandwidth, is limited. Therefore, the design of efficient network control mechanisms for optimizing the capabilities of complex networks is becoming an increasingly critical aspect in networking. In this thesis, we explore the application of optimization techniques to resource allocation in wireless systems. We formulate the optimal network operation as the solution to a network utility maximization problem, which highlights how system performance can be improved if the traditionally separated network layers are jointly optimized. The advantage of such cross-layer optimization is twofold: firstly, joint optimization across layers reveals the true performance limits that can be achieved by practical protocols, and is hence useful for network design or performance analysis; secondly, distributed optimization techniques can be used to systematically engineer protocols and signalling schemes that ensure the globally optimal system operation.

    Within this framework, we consider several challenging problems. The first one considers the design of jointly optimal power and end-to-end rate allocation schemes in multi-hop wireless networks that adhere to the natural time-scales of transport and physical layer mechanisms and impose limited signalling overhead. To validate the theoretical development, we present a detailed implementation of a cross-layer networking stack for DS-CDMA ad-hoc networks in the network simulator ns-2. This implementation exercise reveals several critical issues that arise in practice, but are typically neglected in the theoretical protocol design. Second, we consider networks employing resource scheduling at the data link layer, and we develop detailed distributed solutions for joint end-to-end communication rate selection, multiple time-slot transmission scheduling and power allocation that achieve the optimal network utility. We show with examples how the mathematical framework can be applied to optimize the resource allocation in spatial-reuse time division multiple access (S-TDMA) networks and orthogonal frequency division multiple access (OFDMA) networks. We then make a slight shift in focus, and consider off-line cross-layer optimization to investigate the benefits of various routing strategies in multi-hop networks, and apply these results to a techno-economical feasibility study of cellular relaying networks. Finally, we consider the design of efficient resource scheduling schemes for deadline-constrained real-time traffic in wireless sensor networks. Specifically, we develop theory and algorithms for time- and channel-optimal scheduling of networks operating according to the recent Wireless HART standard.

     

  • 16.
    Soldati, Pablo
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Björn
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Distributed optimization of end-to-end rates and radio resources in WiMax single-carrier networks2006In: GLOBECOM - IEEE Global Telecommunications Conference, 2006Conference paper (Refereed)
    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.

  • 17.
    Soldati, Pablo
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Björn
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Proportionally fair allocation of end-to-end bandwidth in STDMA wireless networks2006In: Proceedings of the International Symposium on Mobile Ad Hoc Networking and Computing, 2006, no MobiHoc), 200, p. 286-297Conference paper (Refereed)
    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.

  • 18.
    Soldati, Pablo
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    A low-signalling scheme for distributed resource allocation in multi-cellular OFDMA systems2008In: GLOBECOM 2008 - 2008 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE   , 2008, p. 3718-3723Conference paper (Refereed)
    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.

  • 19.
    Soldati, Pablo
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    A mathematical programming approach to deadline-constrained transmission scheduling in wireless HART networks2008Conference paper (Refereed)
    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.

  • 20.
    Soldati, Pablo
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    Network-wide resource optimization of wireless OFDMA mesh networks with multiple radios2007In: 2007 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, 2007, p. 4979-4984Conference paper (Refereed)
    Abstract [en]

    We consider the problem of joint end-to-end rate optimization and radio resource management in wireless OFDMA-based mesh networks. Radio units equipped with multiple radio interfaces are combined with the OFDMA medium access scheme to make up for the classical limitations of single-carrier wireless networks. We pose the problem as a utility maximization problem subject to link-rate constraints, power control and transmission scheduling in terms of time slots, channels and radio interfaces. The optimal solution to this problem is in general hard to achieve, both in theory and in practice. We propose an alternative solution approach that drastically reduces the computation time, and suggest a heuristic scheme that attempts to reduce the computation time even further while maintaining the overall system performance close to the optimal. For each scheme we validate the theoretical framework and quantify the performance with numerical examples.

  • 21.
    Soldati, Pablo
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Reducing signaling and respecting time-scales in cross-layer protocols design for wireless networks2009In: GLOBECOM 2009 - 2009 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, 2009, p. 3984-3991Conference paper (Refereed)
    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.

  • 22.
    Soldati, Pablo
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fodor, Gabor
    Ericsson Research, Sweden.
    Sorrentino, Stefano
    Ericsson Research, Sweden.
    On pilot dimensioning in multicell single input multiple output systems2011In: 2011 IEEE GLOBECOM Workshops, GC Wkshps 2011, IEEE , 2011, p. 1382-1387Conference paper (Refereed)
    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.

  • 23.
    Soldati, Pablo
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Zhang, Haibo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Deadline-constrained transmission scheduling and data evacuation in wireless HART networks2009In: Proceedings of ECC, 2009, p. 4320-4325Conference paper (Refereed)
    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.

  • 24.
    Soldati, Pablo
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Zhang, Haibo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Zou, Zhenhua
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Optimal Routing and Scheduling of Deadline-Constrained Traffic Over Lossy Networks2010In: 2010 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE GLOBECOM 2010, 2010Conference paper (Refereed)
    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.

  • 25.
    Timus, Bogdan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    A Joint Routing-MAC Model for Cellular-Relaying Networks2008In: 2008 IEEE 19TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, NEW YORK: IEEE , 2008, p. 1214-1219Conference paper (Refereed)
    Abstract [en]

    We present an iterative joint scheduling-routing algorithm for characterizing the long-term performance of a cellular-relaying network. The physical layer model is based on ideal rate adaptation, fixed transmission power, and average interference. At the MAC layer, time-shares of a common channel are allocated to links in a CSMA/CA-like fashion. At the transport layer, one or more parallel routes can transfer the data flow from a source to the destination, and the average end-user rates are adjusted so as to maximize a global utility function. The general problem of allocating time-shares and selecting link rates is nonconvex. We propose an iterative algorithm and a novel approximation for the physical layer so as to obtain a convex formulation at each iteration step. If only one route is available per source, the problem admits a convex equivalent formulation and the iterative algorithm converges to the global optimum. If more routes per source are available, the problem remains nonconvex. However we show in a simple tractable example that the joint formulation yields sum-log-utility values comparable to the results obtained through exhaustive search of all possible route combinations.

  • 26.
    Timus, Bogdan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Cellular-Relaying Network Dimensioning with Cross-Layer Resource Allocation2008In: 2008 IEEE 19TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, NEW YORK: IEEE , 2008, p. 1236-1240Conference paper (Refereed)
    Abstract [en]

    The enhancement of cellular networks with relaying technologies is expected to bring significant techno-economic benefits, but proper allocation of resources may be a challenging task. This paper addresses the question whether cross-layer optimization is essential for obtaining the expected relaying benefits. We present a network dimensioning approach based on joint routing and radio resource allocation. We consider a macro-cellular scenario with a max-min user-rate objective. If a single route per source is fixed, rates and time-shares can be optimally allocated to each link. In a simple macro-cellular propagation environment, the relays must cost at most 10-25% of a base station cost, if the network is deployed at once. The results are only slightly better when the routing is included in the joint resource allocation.

  • 27.
    Timus, Bogdan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Kim, Dongwoo
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Cross-Layer Resource Allocation Model for Cellular-Relaying Network Performance Evaluation2011In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 60, no 6, p. 2765-2776Article in journal (Refereed)
    Abstract [en]

    The enhancement of cellular networks with relaying technologies is expected to bring significant technoeconomic benefits at the expense of more complex resource allocation. Suitable models for solving network dimensioning problems in cellular-relaying networks must handle radio resource allocation among hundreds of links and tackle interactions between networking layers. For this purpose, we propose a novel cross-layer resource allocation model based on average interference and ideal rate adaptation for the physical layer (PHY), time shares for the medium access layer, and fluid flows for the transport and network layers. We formulate a centralized social welfare maximization problem. When the routes are selected with an a priori algorithm, we show that the resource allocation problem admits an equivalent convex formulation. We show a numerical example for how to use the proposed framework for configuring the backhaul link in a practical relaying network. The overall problem of selecting routes and allocating time shares and link rates is nonconvex. We propose an iterative suboptimal algorithm to solve the problem based on a novel approximation of PHY. We state and prove several convergence properties of the algorithm and show that it typically outperforms routing based on signal-to-noise ratio only.

  • 28.
    Timus, Bogdan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Implications of fairness criteria on the techno-economic viability of relaying networks2009In: 2009 IEEE VEHICULAR TECHNOLOGY CONFERENCE, 2009, p. 3050-3054Conference paper (Refereed)
    Abstract [en]

    The introduction of relaying techniques into cellular networks is expected to reduce the total infrastructure cost, especially when coverage extension is sought. With the advent of networks such as LTE, guaranteeing high data-rate coverage may become a challenge even for incumbent operators which nowadays provide full coverage for voice service. However it is not straightforward that operators will be able (or want) to guarantee coverage for the high data-rates. In this paper we study how the techno-economic viability of the relaying solution depends on the type of service to be provided by the operator. We exemplify the trade off between coverage and system throughput with two fairness criteria: perfect fairness (coverage guarantee) and proportional fairness. We show that relays provide advantages when the operator is interested in providing bit-rate/QoS guarantees. When maximizing the system throughput or cell capacity, relays are of less value.

  • 29.
    Zhang, Haibo
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Optimal Link Scheduling and Channel Assignment for Convergecast in Linear Wireless HART Networks2009In: 2009 7TH INTERNATIONAL SYMPOSIUM ON MODELING AND OPTIMIZATION IN MOBILE, AD HOC, AND WIRELESS, NEW YORK: IEEE , 2009, p. 82-89Conference paper (Refereed)
    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.

  • 30.
    Zhang, Haibo
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Österlind, F.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Voigt, T.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Rapid convergecast on commodity hardware: Performance limits and optimal policies2010In: SECON 2010 - 2010 7th Annual IEEE Communications Society Conference on Sensor, 2010, Vol. Mesh and Ad Hoc Communications and NetworksConference paper (Refereed)
    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.

  • 31.
    Zou, Zhenhua
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES).
    Zhang, Haibo
    KTH, School of Electrical Engineering (EES).
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Delay-constrained maximum reliability routing over lossy links2010In: Proceedings of the IEEE Conference on Decision and Control, IEEE , 2010, p. 973-978Conference paper (Refereed)
    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.

1 - 31 of 31
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