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  • 1.
    Ahani, Ghafour
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Yuan, Di
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Zhao, Yixin
    Nanjing Univ Sci & Technol, Sch Automat, Nanjing 210094, Peoples R China..
    Age-Optimal UAV Scheduling for Data Collection With Battery Recharging2021Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 25, nr 4, s. 1254-1258Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study route scheduling of a UAV for data collection from sensor nodes (SNs) with battery recharging. The freshness of the collected information is captured by the metric of age of information (AoI). The objective is to minimize the average AoI cost of all SNs over a scheduling time horizon. We prove that the problem in its general form is NP-hard. Then, for a special case of the problem, we prove that optimum can be computed in polynomial time. Next, we develop an algorithm based on graph labeling. Finally, we show the effectiveness of our algorithm in comparison to greedy scheduling.

  • 2. Alinia, Bahram
    et al.
    Yousefi, Hamed
    Talebi Mazraeh Shahi, Mohammad Sadegh
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Khonsari, Ahmad
    Maximizing Quality of Aggregation in Delay-Constrained Wireless Sensor Networks2013Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, nr 11, s. 2084-2087Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this letter, both the number of participating nodes and spatial dispersion are incorporated to establish a bi-objective optimization problem for maximizing the quality of aggregation under interference and delay constraints in tree-based wireless sensor networks (WSNs). The formulated problem is proved to be NP-hard with respect to Weighted-sum scalarization and a distributed heuristic aggregation scheduling algorithm, named SDMAX, is proposed. Simulation results show that SDMAX not only gives a close approximation of the Pareto-optimal solution, but also outperforms the best, to our knowledge, existing alternative proposed so far in the literature.

    Fulltekst (pdf)
    Lett1
  • 3.
    Al-Salihi, Hayder
    et al.
    The Department of Informatics, King’s College London, UK.
    Van Chien, Trinh
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Le, Tuan Anh
    The Department of Design Engineering and Mathematics, Middlesex University, London, UK.
    Nakhai, Mohammad Reza
    The Department of Informatics, King’s College London, London, UK.
    A Successive Optimization Approach to Pilot Design for Multi-Cell Massive MIMO Systems2018Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, nr 5, s. 1086-1089Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this letter, we introduce a novel pilot designapproach that minimizes the total mean square errors of theminimum mean square error estimators of all base stations (BSs)subject to the transmit power constraints of individual users inthe network, while tackling the pilot contamination in multicellmassive MIMO systems. First, we decompose the originalnon-convex problem into distributed optimization sub-problemsat individual BSs, where each BS can optimize its own pilotsignals given the knowledge of pilot signals from the remainingBSs. We then introduce a successive optimization approach totransform each optimization sub-problem into a linear matrixinequality form, which is convex and can be solved by availableoptimization packages. Simulation results confirm the fast convergenceof the proposed approach and prevails a benchmarkscheme in terms of providing higher accuracy.

    Fulltekst (pdf)
    fulltext
  • 4.
    Anderlind, Erik
    et al.
    KTH, Tidigare Institutioner (före 2005), Signaler, sensorer och system.
    Zander, Jens
    KTH, Tidigare Institutioner (före 2005), Signaler, sensorer och system.
    A Traffic Model for Non-Real-Time Data Users in Wireless Radio Networks1997Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 1, nr 2, s. 37-39Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Based on an analysis of Internet protocols for data communication, we propose a simple model for future data traffic in wireless radio networks. Model parameters are selected so as to resemble traffic from the Worldwide Web (WWW) access and from distributed file systems. By changing a single parameter, the model can be switched between resembling up- or down-link traffic. The model is intended for design and performance analysis of radio resource allocation algorithms in future wireless systems.

  • 5.
    Andersson, Mattias
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Rathi, Vishwambhar
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Kliewer, Jorg
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Nested Polar Codes for Wiretap and Relay Channels2010Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 14, nr 8, s. 752-754Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We show that polar codes asymptotically achieve the whole capacity-equivocation region for the wiretap channel when the wiretapper's channel is degraded with respect to the main channel, and the weak secrecy notion is used. Our coding scheme also achieves the capacity of the physically degraded receiver-orthogonal relay channel. We show simulation results for moderate block length for the binary erasure wiretap channel, comparing polar codes and two edge type LDPC codes.

    Fulltekst (pdf)
    fulltext
  • 6.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Chen, Lei
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Optimal and Collaborative Rate Selection for Interference Cancellation in Wireless Networks2011Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 15, nr 8, s. 819-821Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Analysis of wireless systems commonly assumes single-user detection at the receivers. Interference is typically treated as noise. On the other hand, multiuser detection has long been taking advantage of interference cancellation (IC) to increase capacity. We exploit IC by optimal rate selection. Transmission rates are collaboratively optimized to maximize the benefit of IC. A link reduces its rate, if that enables IC to significantly boost the SINR on other links. We provide a complexity analysis and an integer programming model to find the optimal IC pattern. Simulation results indicate that throughput improvement is over 30% in low SINR regimes.

    Fulltekst (pdf)
    fulltext
  • 7.
    Athanasiou, George
    et al.
    Digital Systems Department, University of Piraeus, Piraeus, Greece.
    Tsagkaris, Kostas
    Vlacheas, Panagiotis
    Karvounas, Dimitrios
    Demestichas, Panagiotis
    Multi-Objective Traffic Engineering for Future Networks2012Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 16, nr 1, s. 101-103Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An important goal towards the design of Future Networks is to achieve the best ratio of performance to energy consumption and at the same time assure manageability. This paper presents a general problem formulation for Energy-Aware Traffic Engineering and proposes a distributed, heuristic Energy-Aware Traffic Engineering scheme (ETE) that provides load balancing and energy-awareness in accordance with the operator's needs. Simulation results of ETE compared to the optimal network performance confirm the capability of ETE to meeting the needs of Future Networks.

  • 8.
    Athanasiou, Georgios
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Weeraddana, Pradeep Chathuranga
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Auction-Based Resource Allocation in MillimeterWave Wireless Access Networks2013Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, nr 11, s. 2108-2111Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The resource allocation problem of optimal assignment of the stations to the available access points in 60 GHz millimeterWave wireless access networks is investigated. The problem is posed as a multi-assignment optimization problem. The proposed solution method converts the initial problem to a minimum cost flow problem and allows to design an efficient algorithm by a combination of auction algorithms. The solution algorithm exploits the network optimization structure of the problem, and thus is much more powerful than computationally intensive general-purpose solvers. Theoretical and numerical results evince numerous properties, such as optimality, convergence, and scalability in comparison to existing approaches.

  • 9. Bao, Vo Nguyen Quoc
    et al.
    Duong, Quang Trung
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    da Costa, Daniel Benevides
    Alexandropoulos, George C.
    Nallanathan, A.
    Cognitive Amplify-and-Forward Relaying with Best Relay Selection in Non-Identical Rayleigh Fading2013Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, nr 3, s. 475-478Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper investigates several important performance metrics of cognitive amplify-and-forward (AF) relay networks with a best relay selection strategy and subject to nonidentical Rayleigh fading. In particular, assuming a spectrum sharing environment consists of one secondary user (SU) source,K SU relays, one SU destination, and one primary user (PU) receiver, closed-form expressions for the outage probability (OP), average symbol error probability (SEP), and ergodic capacity of the SU network are derived. The correctness of the proposed analysis is corroborated via Monte Carlo simulations and readily allows us to evaluate the impact of the key system parameters on the end-to-end performance. An asymptotic analysis is also carried out and reveals that the diversity gain is defined by the number of relays pertaining to the SU network (i.e., K), being therefore not affected by the interference power constraint of the PU network.

  • 10.
    Bellalta, Boris
    et al.
    Universitat Pompeu Fabra, Barcelona, Spain.
    Barcelo, Jaume
    Universidad Carlos III, Madrid, Spain.
    Staehle, Dirk
    University of Wurzburg, Wurzburg, Germany.
    Vinel, Alexey
    Department of Communications Engineering, Tampere University of Technology, Tampere, Finland.
    Oliver, Miquel
    Universitat Pompeu Fabra, Barcelona, Spain.
    On the performance of packet aggregation in IEEE 802.11ac MU-MIMO WLANs2012Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 16, nr 10, s. 1588-1591Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multi-user spatial multiplexing combined with packet aggregation can significantly increase the performance of Wireless Local Area Networks (WLANs). In this letter, we present and evaluate a simple technique to perform packet aggregation in IEEE 802.11ac MU-MIMO (Multi-user Multiple Input Multiple Output) WLANs. Results show that in non-saturation conditions both the number of active stations (STAs) and the queue size have a significant impact on the system performance. If the number of STAs is excessively high, the heterogeneity of destinations in the packets contained in the queue makes it difficult to take full advantage of packet aggregation. This effect can be alleviated by increasing the queue size, which increases the chances of scheduling a large number of packets at each transmission, hence improving the system throughput at the cost of a higher delay. © 1997-2012 IEEE.

    Fulltekst (pdf)
    fulltext
  • 11.
    Bellalta, Boris
    et al.
    Universitat Pompeu Fabra, Barcelona, Spain.
    Belyaev, Evgeny
    Tampere University of Technology, Finland.
    Jonsson, Magnus
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Vinel, Alexey
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Performance evaluation of IEEE 802.11p-enabled vehicular video surveillance system2014Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 18, nr 4, s. 708-711Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Prospective IEEE 802.11p-based vehicular surveillance system, where video from the vehicle on-board camera is transmitted to the management center, is considered. Multi-hop transmission from the vehicle to the nearest roadside unit and then-via other roadside units-to the gateway is addressed. In this letter we assess the feasibility of such system by analyzing the video end-to-end distortion for a target vehicle, located several hops away from the gateway, when it is alone or there are also other vehicles transmitting video. We demonstrate the importance of dynamic adaptation of the video bit rate of each vehicle depending on the number and positions of the participating vehicles. © 2014 IEEE.

  • 12.
    Belyaev, Evgeny
    et al.
    Tampere University of Technology, Tampere, Finland .
    Vinel, Alexey
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES). Tampere University of Technology, Tampere, Finland.
    Egiazarian, Karen
    Tampere University of Technology, Tampere, Finland.
    Koucheryavy, Yevgeni
    Tampere University of Technology, Tampere, Finland.
    Power Control in See-Through Overtaking Assistance System2013Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, nr 3, s. 612-615, artikkel-id 6423758Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In recently proposed cooperative overtaking assistance systems a video stream captured by a windshield-mounted camera in a vehicle is compressed and broadcast to the vehicle driving behind it, where it is displayed to the driver. It has been shown that this system can provide robust operation if video codec channel adaptation is undertaken by exploiting information from the cooperative awareness messages about any forthcoming increases in the multiple access channel load. In this letter we demonstrate the gains achievable in system performance when the video transmitter power control is also used. © 1997-2012 IEEE.

  • 13.
    Ben Slimane, Slimane
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Approximation to the Symmetric Capacity of Rayleigh Fading Channels with Multi-Level Signals2006Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 0, nr 3, s. 129-131Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A simple approximation for the symmetric capacity of Rayleigh fading channels with finite input alphabet and ideal channel state information is proposed in this letter. This approximation is quite tight over all SNR ranges and can be considered as a good alternative for estimating the symmetric channel capacity for both AWGN and Rayleigh fading channels.

  • 14. Berggren, F.
    et al.
    Zander, Jens
    KTH, Tidigare Institutioner (före 2005), Signaler, sensorer och system.
    Throughput and energy consumption tradeoffs in pathgain-based constrained power control in ALOHA networks2000Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 4, nr 9, s. 283-285Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Power control has been proposed as a tool to improve the performance of packet radio systems in terms of increased throughput and battery lifetime for mobile terminals. In this paper we study the tradeoff between transmitter dynamic range, average energy consumption and the achievable throughput for a simple pathgain based power control algorithm in a slotted ALOHA radio system. The results show that increasing the throughput significantly by means of transmitter power control requires only a very moderate increase in energy consumption and transmitter dynamic range.

  • 15.
    Berggren, Fredrik
    et al.
    KTH, Tidigare Institutioner (före 2005), Signaler, sensorer och system.
    Ben Slimane, Slimane
    KTH, Tidigare Institutioner (före 2005), Signaler, sensorer och system.
    A simple bound on the outage probability with lognormal interferers2004Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 8, nr 5, s. 271-273Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider the problem of determining the outage probability in a cellular radio system, where the interference is modeled by a sum of lognormal random variables. As no closed form expression is known, bounds can serve as a quick way of evaluating performance. By applying the arithmeticgeometric mean inequality, we give a lower bound, computationally simple as it is expressed by a single Q-function. The bound includes the case of correlated interferers and background noise. Numerical evaluation for a range of parameters valid for practical applications, shows good accuracy for moderate variances and improvement over a previously suggested bound. This is especially emphasized when the number of interferers is large.<

  • 16.
    Björnson, Emil
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Zetterberg, Per
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Bengtsson, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Capacity Limits and Multiplexing Gains of MIMO Channels with Transceiver Impairments2013Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, nr 1, s. 91-94Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The capacity of ideal MIMO channels has a high-SNR slope that equals the minimum of the number of transmit and receive antennas. This letter analyzes if this result holds when there are distortions from physical transceiver impairments. We prove analytically that such physical MIMO channels have a finite upper capacity limit, for any channel distribution and SNR. The high-SNR slope thus collapses to zero. This appears discouraging, but we prove the encouraging result that the relative capacity gain of employing MIMO is at least as large as with ideal transceivers.

    Fulltekst (pdf)
    fulltext
  • 17.
    Braga Jr, Iran M.
    et al.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil..
    Antonioli, Roberto P.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil..
    Fodor, Gabor
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. Ericsson Res, S-16480 Stockholm, Sweden..
    Silva, Yuri C. B.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil..
    Freitas Jr, Walter C.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil..
    Joint Pilot and Data Power Control Optimization in the Uplink of User-Centric Cell-Free Systems2022Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 26, nr 2, s. 399-403Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Joint pilot and data power control (JPDPC) is known to have a large impact on both the overall spectral/energy efficiency and fairness of cell-based systems. However, the impact of JPDPC on the inherent spectral/energy efficiency and fairness trade-off in cell-free (CF) systems is much less understood. In this letter, considering pilot contamination, user-centric clustering and multi-antenna access points, we formulate novel JPDPC problems in CF systems as distinct optimization tasks, whose objectives are maximizing the minimum spectral efficiency (SE), maximizing the total SE and maximizing the product of the individual signal-to-interference-plus-noise ratios. Since these problems are non-convex, we solve them by combining successive convex approximation and geometric programming. To the best of our knowledge, this is the first letter analyzing and optimizing JPDPC in user-centric CF systems. Our results indicate that JPDPC allows users to save more energy than the disjoint optimization of pilot and data powers when maximizing the minimum SE, while showing that JPDPC plays a crucial role in balancing between SE and fairness also in CF systems.

  • 18.
    Braga Jr, Iran M.
    et al.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil..
    Cavalcante, Eduardo de O.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil.;Fed Inst Educ Sci & Technol Ceara, BR-63660000 Taua, Brazil..
    Fodor, Gabor
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. Ericsson Res, S-16480 Stockholm, Sweden..
    Silva, Yuri C. B.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil..
    e Silva, Carlos F. M.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil..
    Freitas Jr, Walter C.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil..
    User Scheduling Based on Multi-Agent Deep Q-Learning for Robust Beamforming in Multicell MISO Systems2020Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 24, nr 12, s. 2809-2813Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Maximizing the rate in multiple input single output (MISO) systems using distributed algorithms is an important task that typically incurs high computational cost. In this work, we propose two deep Q-learning-based user scheduling schemes to solve the beamforming problem of sum-rate maximization with per base station power constraints in multicell MISO scenarios. The two key features of the proposed algorithms are that they are executed in a distributed fashion and are robust with respect to channel state information (CSI) errors. Simulation results show that in the presence of CSI errors the proposed schemes outperform state-of-the-art algorithms both in terms of average spectral efficiency and execution time.

  • 19.
    Brännström, Fredrik
    et al.
    Chalmers University of Technology.
    Graell i Amat, Alexandre
    Telecom Bretagne, France.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    A general structure for rate-compatible concatenated codes2007Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 11, nr 5, s. 437-439Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this letter, a general concatenated code structure is presented, encompassing both parallel and serially concatenated codes as special cases. The structure provides a unifying framework for the analysis of concatenated codes and offers new degrees of freedom for code design. Performance analysis based on error bounds in the error floor region and suggestions for suitable design criteria are provided, together with a design approach for the waterfall region. The proposed structure allows for constructing very high-rate codes with no penalty in the error floor region and good performance in the waterfall region.

  • 20.
    Campolo, Claudia
    et al.
    DIIES Department, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Molinaro, Antonella
    DIIES Department, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy, & CentraleSupélec/L2S, Université Paris-Saclay, Paris, France.
    Berthet, Antoine
    CentraleSupélec/L2S, Université Paris-Saclay, Paris, France.
    Vinel, Alexey
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES). Department of Electrical Engineering, Western Norway University of Applied Sciences, Bergen, Norway.
    On Latency and Reliability of Road Hazard Warnings over the Cellular V2X Sidelink Interface2019Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 23, nr 11, s. 2135-2138Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Decentralized Environmental Notification Messages (DENMs) are generated by a vehicle upon detection of an accident or other hazards on the road, and need to be promptly and reliably transmitted. Delayed or lost messages may have fatal consequences, especially in critical driving situations, such as automated overtake and emergency braking, when vehicles can be very close to each other. In this letter, the DENM latency and reliability performances are characterized over the Cellular Vehicle-to-everything (C-V2X) sidelink (PC5 interface). The conducted study uses analytical tools, among which stochastic geometry, to derive performance results, then validated by simulations. Results are applied to the case of DENMs for emergency electronic brake lights, and helpful insights are provided for this crucial case and for other more general DENM-assisted V2X use cases.

  • 21.
    Campolo, Claudia
    et al.
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Molinaro, Antonella
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Vinel, Alexey
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Zhang, Yan
    Simula Research Laboratory, Fornebu, Norway.
    Modeling Event-Driven Safety Messages Delivery in IEEE 802.11p/WAVE Vehicular Networks2013Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, nr 12, s. 2392-2395Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A stochastic model is designed to assess the delivery performance of event-driven safety messages in IEEE 802.11p/1609.4 vehicular ad-hoc networks (VANETs). The study focuses on the case of a vehicle detecting an unpredictable hazard and broadcasting the alert in the one-hop neighborhood. The model aims at providing quick insights into the impact of the latest WAVE specifications (i.e., traffic differentiation, channel switching) on the delivery of such short-lived alert messages. Results prove that it is accurate in capturing the effect of relevant parameters and show that repeating the alert transmission on the control channel helps to achieve reliable delivery. © 2013 IEEE.

  • 22.
    Campolo, Claudia
    et al.
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Italy.
    Vinel, Alexey
    Department of Communications Engineering, Tampere University of Technology.
    Molinaro, Antonella
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Italy.
    Koucheryavy, Yevgeni
    Department of Communications Engineering, Tampere University of Technology.
    Modeling Broadcasting in IEEE 802.11p/WAVE Vehicular Networks2011Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 15, nr 2, s. 199-201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    IEEE 802.11p/WAVE (Wireless Access in Vehicular Environments) is an emerging family of standards intended to support wireless access in Vehicular Ad Hoc Networks (VANETs). Broadcasting of data and control packets is expected to be crucial in this environment. Both safety-related and non-safety applications rely on broadcasting for the exchange of data or status and advertisement messages. Most of the broadcasting traffic is designed to be delivered on a given frequency during the control channel (CCH) interval set by the WAVE draft standard. The rest of the time, vehicles switch over to one of available service channels (SCHs) for non-safety related data exchange. Although broadcasting in VANETs has been analytically studied, related works neither consider the WAVE channel switching nor its effects on the VANET performance. In this letter, a new analytical model is designed for evaluating the broadcasting performance on CCH in IEEE 802.11p/WAVE vehicular networks. This model explicitly accounts for the WAVE channel switching and computes packet delivery probability as a function of contention window size and number of vehicles. © 2011 IEEE.

    Fulltekst (pdf)
    fulltext
  • 23.
    Cao, Le Phuong
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Oechtering, Tobias J.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Skoglund, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Transmit Beamforming for Single-User Large-Scale MISO Systems With Sub-Connected Architecture and Power Constraints2018Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, nr 10, s. 2096-2099Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This letter considers optimal transmit beamforming for a sub-connected large-scale MISO system with RF chain and per-antenna power constraints. The system is configured such that each RF chain serves a group of antennas. For the hybrid scheme, necessary and sufficient conditions to design the optimal digital and analog precoders are provided. It is shown that, in the optimum, the optimal phase shift at each antenna has to match the channel coefficient and the phase of the digital precoder. In addition, an iterative algorithm is provided to find the optimal power allocation. We study the case where the power constraint on each RF chain is smaller than the sum of the corresponding per-antenna power constraints. Then, the optimal power is allocated based on two properties: each RF chain uses full power and if the optimal power allocation of the unconstraint problem violates a per-antenna power constraint then it is optimal to allocate the maximal power for that antenna.

    Fulltekst (pdf)
    fulltext
  • 24.
    Charalambous, Themistoklis
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Nomikos, Nikolaos
    Krikidis, Ioannis
    Vouyioukas, Demosthenes
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Modeling Buffer-Aided Relay Selection in Networks With Direct Transmission Capability2015Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, nr 4, s. 649-652Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider a wireless relay network that consists of a source, half-duplex decode-and-forward buffer-aided relays and a destination. While the majority of previous works on relay selection assume no direct transmission between source and destination in such a setting, we lift this assumption and propose a link selection policy that exploits both the buffering ability and the opportunity for successful reception of a packet directly from the source. The proposed relay selection scheme incorporates the instantaneous strength of the wireless links and adapts the relay selection decision based on the strongest available link. The evolution of the network as a whole is modeled by means of a Markov chain and thus, the outage probability is associated with the steady state of the Markov chain. It is deduced that even if the link between the source and the destination is in principle a very unreliable link, it is always beneficial for the source to multicast a packet to both the relay with the strongest available link and the destination.

  • 25.
    Chen, Bolin
    et al.
    Univ Sheffield, Dept Elect & Elect Engn, Sheffield S38AN, S Yorkshire, England.
    You, Lei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Yuan, Di
    Linkoping Univ, Dept Sci & Technol, S-60174 Norrkoping, Sweden.
    Pappas, Nikolaos
    Linkoping Univ, Dept Sci & Technol, S-60174 Norrkoping, Sweden.
    Zhang, Jie
    Univ Sheffield, Dept Elect & Elect Engn, Sheffield S38AN, S Yorkshire, England.
    Resource Optimization for Joint LWA and LTE-U in Load-Coupled and Multi-Cell Networks2019Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 23, nr 2, s. 330-333Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider the performance optimization of multi-cell networks with LTE and Wi-Fi aggregation (LWA) and LTE-unlicensed (LTE-U) with sharing of the unlicensed band. Theoretical results are derived to enable an algorithm to approach the optimum. Numerical results show the algorithm's effectiveness and benefits of joint use of LWA and LTE-U.

  • 26.
    Chen, Bolin
    et al.
    Univ Sheffield, England.
    You, Lei
    Uppsala Univ, Sweden.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Zhang, Jie
    Univ Sheffield, England.
    Resource Optimization for Joint LWA and LTE-U in Load-Coupled and Multi-Cell Networks2019Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 23, nr 2, s. 330-333Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider the performance optimization of multi-cell networks with LTE and Wi-Fi aggregation (LWA) and LTE-unlicensed (LTE-U) with sharing of the unlicensed band. Theoretical results are derived to enable an algorithm to approach the optimum. Numerical results show the algorithms effectiveness and benefits of joint use of LWA and LTE-U.

    Fulltekst (pdf)
    fulltext
  • 27.
    Chen, Jiajia
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Chen, Biao
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    A novel algorithm for intra-ONU bandwidth allocation in ethernet passive optical networks2005Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 9, nr 9, s. 850-852Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel decentralized algorithm is introduced for the intra-ONU bandwidth allocation in an Ethernet Passive Optical Network (EPON). The algorithm is of low computational complexity, and can guarantee both the priority and fairness of the differentiated services. Simulation results are presented and compared with those of two existing bandwidth allocation algorithms.

  • 28.
    Chen, Zheng
    et al.
    University of Paris Sud, France.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Kountouris, Marios
    Huawei Technology Co Ltd, France.
    Probabilistic Caching in Wireless D2D Networks: Cache Hit Optimal Versus Throughput Optimal2017Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, nr 3, s. 584-587Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Departing from the conventional cache hit optimization in cache-enabled wireless networks, we consider an alternative optimization approach for the probabilistic caching placement in stochastic wireless D2D caching networks taking into account the reliability of D2D transmissions. Using tools from stochastic geometry, we provide a closed-form approximation of cache-aided throughput, which measures the density of successfully served requests by local device caches, and we obtain the optimal caching probabilities via numerical optimization. Compared with the cache-hit-optimal case, the optimal caching probabilities obtained by cache-aided throughput optimization show notable gain in terms of the density of successfully served user requests, particularly in dense user environments.

    Fulltekst (pdf)
    fulltext
  • 29.
    Chen, Zhengchuan
    et al.
    Chongqing Univ, Peoples R China.
    Lang, Kang
    Chongqing Univ, Peoples R China.
    Yang, Howard H.
    Univ Illinois, IL USA; Zhejiang Univ, Peoples R China.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Wang, Min
    Chongqing Univ Posts & Telecommun, Peoples R China; Guilin Univ Elect Technol, Peoples R China.
    Quek, Tony Q. S.
    Singapore Univ Technol & Design, Singapore.
    Age of Information of a Dual Queue Status Update System: A Stochastic Hybrid Systems Method2023Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 27, nr 7, s. 1714-1718Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using redundant devices to update the status can improve the robustness against transmission failure, thus improving timeliness of information. However, out of order update arrivals resulting from multiple devices impose a significant challenge to the analysis of timeliness of information in such systems. This letter studies the average age of information (AoI) of a dual queue status update system under zero-wait policy. We leverage tools from stochastic hybrid systems to derive closed-form expression for the average AoI of the dual queue system and extend the result to the three-queue system. The results show that the average AoI of the dual queue system can be reduced by 37.5% compared to that using only a single queue.

  • 30.
    Cheng, Yuxin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Fiorani, Matteo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Reliable and Cost Efficient Passive Optical Interconnects for Data Centers2015Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, nr 11, s. 1913-1916Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To address the sustainability, scalability, and reliability problems that data centers are currently facing, we propose three passive optical interconnect (POI) architectures on top of the rack. The evaluation results show that all three architectures offer high reliability performance (connection availability for intra-rack interconnections higher than 99.999%) in a cost-efficient way.

    Fulltekst (pdf)
    fulltext
  • 31. Chien, T. Van
    et al.
    Tu, L. T.
    Chatzinotas, S.
    Ottersten, Björn
    Interdisciplinary Centre for Security, Reliability and Trust (SnT), University of Luxembourg, Luxembourg City, Luxembourg.
    Coverage Probability and Ergodic Capacity of Intelligent Reflecting Surface-Enhanced Communication Systems2021Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 25, nr 1, s. 69-73Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This letter studies the performance of a single-input single-output (SISO) system enhanced by the assistance of an intelligent reflecting surface (IRS), which is equipped with a finite number of elements under Rayleigh fading channels. From the instantaneous channel capacity, we compute a closed-form expression of the coverage probability as a function of statistical channel information only. A scaling law of the coverage probability and the number of phase shifts is further obtained. The ergodic capacity is derived, then a simple upper bound to simplify matters of utilizing the symbolic functions and can be applied for a long period of time. Numerical results manifest the tightness and effectiveness of our closed-form expressions compared with Monte-Carlo simulations.

  • 32.
    Cho, Jeong-woo
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Telekommunikationssystem, TSLab.
    Kim, Seong-Lyun
    Yonsei University.
    Chong, Song
    KAIST (Korea Advanced Institute of Science and Technology).
    Capacity of Interference-Limited Ad Hoc Networks with Infrastructure Support2006Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 10, nr 1, s. 16-18Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this letter, we consider the capacity of ad hoc networks with infrastructure support. Although Grossglauser-Tse mobile network model enables Θ(1) per-node throughput scaling, the mobility assumption may be too unrealistic to be accepted in some practical situations. One of the key observations we acquired is that the infrastructure support plays the same role played by the mobility in the Grossglauser-Tse model. We show that nodes can utilize the randomly located infrastructure support instead of mobility when nodes are nearly static. In this case, we show that the per-node throughput of Θ(1) is still achievable when the number of access points grows linearly with respect to the number of nodes.

    Fulltekst (pdf)
    fulltext
  • 33. Christopoulos, D.
    et al.
    Arnau, J.
    Chatzinotas, S.
    Mosquera, C.
    Ottersten, Björn
    SnTUniversity of Luxembourg, Luxembourg .
    MMSE Performance Analysis of Generalized Multibeam Satellite Channels2013Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, nr 7, s. 1332-1335Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aggressive frequency reuse in the return link (RL) of multibeam satellite communications (SatComs) is crucial towards the implementation of next generation, interactive satellite services. In this direction, multiuser detection has shown great potential in mitigating the increased intrasystem interferences, induced by a tight spectrum reuse. Herein we present an analytic framework to describe the linear Minimum Mean Square Error (MMSE) performance of multiuser channels that exhibit full receive correlation: an inherent attribute of the RL of multibeam SatComs. Analytic, tight approximations on the MMSE performance are proposed for cases where closed form solutions are not available in the existing literature. The proposed framework is generic, thus providing a generalized solution straightforwardly extendable to various fading models over channels that exhibit full receive correlation. Simulation results are provided to show the tightness of the proposed approximation with respect to the available transmit power.

  • 34.
    Chu, Thi My Chinh
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Phan, Hoc
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Dynamic Spectrum Access for Cognitive Radio Networks with Prioritized Traffics2014Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 18, nr 7, s. 1218-1221Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We develop a dynamic spectrum access (DSA) strategy for cognitive radio networks where prioritized traffic is considered. Assume that there are three classes of traffic, one traffic class of the primary user and two traffic classes of the secondary users, namely, Class 1 and Class 2. The traffic of the primary user has the highest priority, i.e., the primary users can access the spectrum at any time with the largest bandwidth demand. Furthermore, Class 1 has higher access and handoff priority as well as larger bandwidth demand as compared to Class 2. To evaluate the performance of the proposed DSA, we model the state transitions for DSA as a multi-dimensional Markov chain with three-state variables which present the number of packets in the system of the primary users, the secondary Class 1, and secondary Class 2. In particular, the blocking probability and dropping probability of the two secondary traffic classes are assessed.

  • 35.
    Chu, Thi My Chinh
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Phan, Hoc
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    On the Performance of Underlay Cognitive Radio Networks Using M/G/1/K Queuing Model2013Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, nr 5, s. 876-879Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Motivated by a realistic scenario for cognitive radio systems, we model the underlay cognitive radio network (CRN) under interference power constraint imposed by the primary network as an M/G/1/K queueing system. The respective embedded Markov chain is provided to analyze several key queueing performance measures. In particular, the equilibrium probabilities of all states are derived and utilized to evaluate throughput, blocking probability, mean packet transmission time, mean number of packets in the system, and mean waiting time of an underlay CRN with Nakagami-m fading channels.

  • 36.
    Chu, Thi My Chinh
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kreativa teknologier.
    Zepernick, Hans-Juergen
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kreativa teknologier.
    Performance of a Non-orthogonal Multiple Access System with Full-Duplex Relaying2018Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, nr 10, s. 2084-2087Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we study a power-domain nonorthogonal multiple access (NOMA) system in which a base station (BS) superimposes the transmit signals to the users. To enhance spectral efficiency and link reliability for the far-distance user, a full-duplex (FD) relay assists the BS while the neardistance user is reached over the direct link. For this setting, we analyze outage probability and sum rate of the NOMA system over Nakagami-m fading with integer fading severity parameter m. Numerical results are provided for outage probability and sum rate to show the effect of system parameters on the performance of the FD NOMA system over Nakagami-m fading. IEEE

  • 37.
    DAndrea, Carmen
    et al.
    Univ Cassino & Southern Latium, Italy; Consorzio Nazl Interuniv Telecomunicaz CNIT, Italy.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Improving Cell-Free Massive MIMO by Local Per-Bit Soft Detection2021Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 25, nr 7, s. 2400-2404Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this letter, we consider the uplink of a cell-free Massive multiple-input multiple-output (MIMO) network where each user is decoded by a subset of access points (APs). An additional step is introduced in the cell-free Massive MIMO processing: each AP in the uplink locally implements soft MIMO detection and then shares the resulting bit log-likelihoods on the front-haul link. The decoding of the data is performed at the central processing unit (CPU), collecting the data from the APs. The non-linear processing at the APs consists of the approximate computation of the posterior density for each received data bit, exploiting only local channel state information. The proposed method offers good performance in terms of frame-error-rate and considerably lower complexity than the optimal maximum-likelihood demodulator.

    Fulltekst (pdf)
    fulltext
  • 38.
    Duc Ho, Chung
    et al.
    Queens University of Belfast, North Ireland.
    Ngo, Hien
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Matthaiou, Michail
    Queens University of Belfast, North Ireland.
    Duong, Trung Q.
    Queens University of Belfast, North Ireland.
    On the Performance of Zero-Forcing Processing in Multi-Way Massive MIMO Relay Networks2017Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, nr 4, s. 849-852Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider a multi-way massive multiple-input multiple-output relay network with zero-forcing processing at the relay. By considering the time-division duplex protocol with channel estimation, we derive an analytical approximation of the spectral efficiency. This approximation is very tight and simple, which enables us to analyze the system performance, as well as to compare the spectral efficiency with zero-forcing and maximum-ratio processing. Our results show that by using a very large number of relay antennas and with the zero-forcing technique, we can simultaneously serve many active users in the same time-frequency resource, each with high spectral efficiency.

  • 39. Duong, Quang Trung
    et al.
    Bao, Vo Nguyen Quoc
    Zepernick, Hans-Jürgen
    On the Performance of Selection Decode-and-Forward Relay Networks over Nakagami-m Fading Channels2009Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 13, nr 3, s. 172-174Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we present the performance of fixed decode-and-forward cooperative networks with relay selection over independent but not identically distributed Nakagamim fading channels, with integer values of the fading severity parameter m. Specifically, closed-form expressions for the symbol error probability and the outage probability are derived using the statistical characteristic of the signal-to-noise ratio. We also perform Monte-Carlo simulations to verify the analytical results

  • 40.
    Duong, Quang Trung
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    da Costa, Daniel Benevides
    Tsiftsis, Theodoros A.
    Zhong, Caijun
    Nallanathan, Arumugam
    Outage and Diversity of Cognitive Relaying Systems under Spectrum Sharing Environments in Nakagami-m Fading2012Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 12, nr 11Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this letter, the outage performance of dualhop cooperative spectrum sharing systems with a direct link is investigated. A selection combining receiver is employed at the destination in order to combine the signals received from the decode-and-forward (DF) relay and from the source. Assuming independent non-identically distributed Nakagami-m fading channels, exact and asymptotic closed-form expressions are derived for the outage probability. Our results reveal that the diversity order of the considered system is solely determined by the fading severity parameters of the secondary network, being equal to min(m1, m2) + m0, where m0, m1, and m2 represent the fading severity parameters of the secondary nodes i.e., source→destination, source→relay, and relay→destination links, respectivel

  • 41.
    Dwivedi, Satyam
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Zachariah, Dave
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    De Angelis, Alessio
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Cooperative Decentralized Localization Using Scheduled Wireless Transmissions2013Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, nr 6, s. 1240-1243Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this letter we develop a solution for decentralized localization of transceiving nodes in wireless networks. By exploiting a common transmission schedule, this is achieved without any additional communication and dispels the need for synchronized nodes. We derive the Cramer-Rao bounds for the solution and formulate two practical estimators for localization. Finally, the solution and estimators are tested in numerical experiments.

  • 42.
    Fiems, Dieter
    et al.
    Ghent University, Ghent, Belgium.
    Vinel, Alexey
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Connectivity Times in Vehicular Networks2018Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, nr 11, s. 2270-2273, artikkel-id 8444968Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose an analytical model that accurately captures the service advertisement and access mechanisms in IEEE 1609.4/IEEE 802.11p multi-channel vehicular networks where road-side units announce non-safety services to passing vehicles on a dedicated channel. For a drive-thru scenario, we calculate various performance measures including the service discovery probability, the mean time till discovery and the channel utilization. © 1997-2012 IEEE.

  • 43.
    Fiorani, Matteo
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Aleksic, Slavisa
    Casoni, Maurizio
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Energy-Efficient Elastic Optical Interconnect Architecture for Data Centers2014Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 18, nr 9, s. 1531-1534Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To address the urgent need for high-capacity, scalable and energy-efficient data center solutions, we propose a novel data center network architecture realized by combining broadcast-and-select approach with elastic channel spacing technology. We demonstrate that the proposed architecture is able to scale efficiently with the number of servers and offers lower energy consumption at a competitive cost compared to the existing solutions.

  • 44.
    Fiorani, Matteo
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Rostami, Ahmad
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Transport Abstraction Models for an SDN-Controlled Centralized RAN2015Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, nr 8, s. 1406-1409Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In a centralized radio access network (C-RAN) scenario the joint coordination of radio (e.g., remote radio units, baseband units) and transport (e.g., optical cross connects) resources can be achieved via software defined networking (SDN) control plane, where a global orchestrator harmonizes the use of resources across all network segments. The more accurate the information about each domain (i.e., the abstraction of wireless and transport resources) is, the better will be the outcome of the orchestration work. This letter presents three transport resources abstraction models along with their corresponding orchestration policies. Their performance are compared showing that there is not a single best abstraction strategy that fits all the cases. If radio resources are scarce compared to transport resources, complex transport abstraction models are not needed. Contrariwise, if enough radio resources are widely available, more detailed abstraction models are required for achieving good network performance, but at the expense of an increased implementation complexity.

  • 45. Fodor, Gabor
    et al.
    Di Marco, Piergiuseppe
    Telek, Miklós
    On Minimizing the MSE in the Presence of Channel State Information Errors2015Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, nr 9, s. 1604-1607Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider the uplink of a multiuser multiple input multiple output (MU MIMO) system, in which the base station acquires channel state information (CSI) for which the estimation error depends on the resources assigned to the uplink pilot symbols. For this system, we first derive the receiver that minimizes the mean square error (MSE) of the uplink detected data symbols, as opposed to the naïve receiver that does not minimize the MSE in the presence of CSI errors. We then derive a closed form expression for the MSE as a function of the employed pilot-to-data power ratio, number of antennas and the MU MIMO interference power. This expression allows us to gain the insight that the gain of using the actual MMSE receiver as opposed to the naïve receiver becomes particularly important when the number of BS antennas is large.

  • 46.
    Fountoulakis, Emmanouil
    et al.
    EURECOM, France; Ericsson, Sweden.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Kountouris, Marios
    EURECOM, France.
    Goal-Oriented Policies for Cost of Actuation Error Minimization in Wireless Autonomous Systems2023Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 27, nr 9, s. 2323-2327Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider the minimization of the cost of actuation error under resource constraints for real-time tracking in wireless autonomous systems. A transmitter monitors the state of a discrete random process and sends updates to a receiver over an unreliable wireless channel. The receiver then takes actions according to the estimated state of the source. For each discrepancy between the real state of the source and the estimated one, we consider a different cost of actuation error. This models the case where some states, and consequently the corresponding actions to be taken, are more important than others. We provide two algorithms, a first one reaching an optimal solution but of high complexity, and a second low-complexity one that provides a suboptimal solution. Our simulation results evince that the performance of the two algorithms are quite close.

  • 47.
    Gerami, Majid
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap.
    Two-Layer Coding in Distributed Storage Systems With Partial Node Failure/Repair2017Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, nr 4, s. 726-729Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We a distributed storage system where parts of the stored packets in storage nodes are subject to being lost. In a process, termed as the partial repair, the lost packets in a faulty node are recovered by the transmitted packets from other storage nodes and the available packets in the faulty node. To improve reliability of the stored data, and reduce the transmission costs, we propose a scheme that implements two-layer coding for storing files in the system. We study the minimum possible partial-repair bandwidth, and the codes that achieve the optimal bound.

  • 48. Gharanjik, Ahmad
    et al.
    Rao, Bhavani Shankar Mysore Rama
    Arapoglou, Pantelis-Daniel
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. University of Luxembourg, Luxembourg.
    Gateway Switching in Q/V Band Satellite Feeder Links2013Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, nr 7, s. 1384-1387Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A main challenge towards realizing the next generation Terabit/s broadband satellite communications (SatCom) is the limited spectrum available in the Ka band. An attractive solution is to move the feeder link to the higher Q/V band, where more spectrum is available. When utilizing the Q/V band, due to heavy rain attenuation, gateway diversity is considered a necessity to ensure the required feeder link availability. Although receive site diversity has been studied in the past for SatCom, there is much less maturity in terms of transmit diversity techniques. In this paper, a modified switch and stay combining scheme is proposed for a Q/V band feeder link, but its performance is also evaluated over an end-to-end satellite link. The proposed scheme is pragmatic and has close to optimal performance with notably lower complexity.

  • 49.
    Grezet, Matthias
    et al.
    Aalto Univ, Finland..
    Westerback, Thomas
    Mälardalens högskola, Akademin för utbildning, kultur och kommunikation, Utbildningsvetenskap och Matematik.
    Freij-Hollanti, Ragnar
    Aalto Univ, Finland..
    Hollanti, Camilla
    Aalto Univ, Finland..
    Uniform Minors in Maximally Recoverable Codes2019Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 23, nr 8, s. 1297-1300Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this letter, locally recoverable codes with maximal recoverability are studied with a focus on identifying the MDS codes resulting from puncturing and shortening. By using matroid theory and the relation between MDS codes and uniform minors, the list of all the possible uniform minors is derived. This list is used to improve the known non-asymptotic lower bound on the required field size of a maximally recoverable code.

  • 50. Gu, Feng
    et al.
    Xie, Chongyang
    Peng, Min
    Cavdar, Cicek
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Khan, Samee
    Ghani, Nasir
    Virtual Overlay Network Scheduling2011Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 15, nr 8, s. 893-895Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As applications continue to expand, there is a growing need to provide advance reservation scheduling for higher-end virtual overlay network services. Hence this work presents an optimization formulation for this problem and studies several heuristic solutions using network simulation.

1234 1 - 50 of 188
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