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  • 1.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Askoxylakis, Ioannis
    FORTH, Institute of Computer Science, Greece.
    Fowler, Scott
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Gundlegård, David
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Traganitis, Apostolos
    FORTH, Institute of Computer Science, Greece.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Security and Resilience in Cognitive Radio Networks2011Ingår i: European Research Consortium for Informatics and Mathematics Magazine, ISSN 0926-4981, nr 85, s. 48-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    After more than a decade of research, system securityand resilience is now the major technological barrier forthe Cognitive Radio (CR) to be adopted by the telecommunication industry. New ideas are required tomake CR networks secure and robust against attacks taking advantage the inherent characteristics of the CR functionality. This work explores key points that urgentlyneed to be addressed.

  • 2.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Avgouleas, Ioannis
    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.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Flexible allocation of heterogeneous resources to services on an IoT device2015Ingår i: 2015 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS), Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 99-100Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the Internet of Things (IoT), devices and gateways may be equipped with multiple, heterogeneous network interfaces which should be utilized by a large number of services. In this work, we model the problem of assigning services' resource demands to a device's heterogeneous interfaces and give a Mixed Integer Linear Program (MILP) formulation for it. For meaningful instance sizes the MILP model gives optimal solutions to the presented computationally-hard problem. We provide insightful results discussing the properties of the results on the properties of the derived solutions with respect to the splitting of services to different interfaces.

  • 3.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Chen, Lei
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    A Fully Decentralized and Load-Adaptive Fractional Frequency Reuse Scheme2011Ingår i: Modeling, Analysis & Simulation of Computer and Telecommunication Systems (MASCOTS), 2011 IEEE 19th International Symposium on, 2011, s. 425-428Konferensbidrag (Refereegranskat)
    Abstract [en]

    A new fully decentralized dynamic fractional frequency reuse (FFR)-based scheme for cellular OFDMA networks is introduced. FFR is a technique to mitigate inter-cell interference to improve the throughput of interference-limited users on the cell edge, to the expense of the rest of the cell's users and the aggregate throughput. The proposed scheme aims to limit the FFR-incurred loss of the center users' throughput, while still providing sufficient bandwidth for the cell edge users' communication. This is done by local information sharing and distributed optimization. The resulting flexibility of frequency reuse can be especially beneficial in scenarios with non-uniform and time-varying load. The optimization task is accomplished by solving a knapsack problem in each cell, where the goal is to maximize the center throughput while maintaining acceptable degradation on the cell edge with respect to the original FFR allocation. The performance improvement resulting from the distributed and dynamic FFR scheme is demonstrated by snapshot simulations on an 81-cells network with asymmetric cell load. The proposed scheme achieves up to a 62% gain in cell-center throughput with a cost of no more than 18% at the edges when compared to the classic FFR scheme. The overall system throughput improvement ranges from 22% to 58%.

  • 4.
    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 Networks2011Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 15, nr 8, s. 819-821Artikel i tidskrift (Refereegranskat)
    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.

  • 5.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Ephremides, Anthony
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    He, Qing
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    On Emptying a Wireless Network in Minimum Time2012Ingår i: 2012 IEEE International Symposium on Information Theory Proceedings (ISIT), Piscataway, NJ, USA: IEEE , 2012, s. 2671-2675Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 6.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Gundlegård, David
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Rydergren, Clas
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Rajna, Botond
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Carlsson, Richard
    Ericsson Research, Services & Software.
    Forgeat, Julien
    Ericsson Research, Services & Software.
    Hu, Tracy H
    Ericsson Research, Services & Software.
    Liu, Evan L
    Ericsson Research, Services & Software.
    Moritz, Simon
    Ericsson Research, Services & Software.
    Zhao, Sky
    Ericsson Research, Services & Software.
    Zheng, Yaotian
    Ericsson Research, Services & Software.
    Mobility modeling for transport efficiency: Analysis of travel characteristics based on mobile phone data2013Ingår i: Netmob 2013: Mobile phone data for development / [ed] Vincent Blondel, 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Signaling data from the cellular networks can provide a means of analyzing the efficiency of a deployed transportation system and assisting in the formulation of transport models to predict its future use. An approach based on this type of data can be especially appealing for transportation systems that need massive expansions, since it has the added benefit that no specialized equipment or installations are required, hence it can be very cost efficient.

    Within this context in this paper we describe how such obtained data can be processed and used in order to act as enablers for traditional transportation analysis models. We outline a layered, modular architectural framework that encompasses the entire process and present results from initial analysis of mobile phone call data in the context of mobility, transport and transport infrastructure. We finally introduce the Mobility Analytics Platform, developed by Ericsson Research, tailored for mobility analysis, and discuss techniques for analyzing transport supply and demand, and give indication on how cell phone use data can be used directly to analyze the status and use of the current transport infrastructure.

  • 7.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Papadakis, Stefanos
    FORTH.
    Traganitis, Apostolos
    FORTH & UoC.
    Vasilios, Siris
    AUEB.
    Adjacent Channel Interference in 802.11a Is Harmful: Testbed Validation of a Simple Quantification Model2011Ingår i: IEEE COMMUNICATIONS MAGAZINE, ISSN 0163-6804, Vol. 49, nr 3, s. 160-166Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wireless LAN radio interfaces based on the IEEE 802.11a standard have lately found widespread use in many wireless applications. A key reason for this was that although the predecessor, IEEE 802.11b/ g, had a poor channelization scheme, which resulted in strangling adjacent channel interference (ACI), 802.11a was widely believed to be ACI-free due to a better channelization combined with OFDM transmission. We show that this is not the case. ACI does exist in 802.11a, and we can quantify its magnitude and predict its results. For this, we present minor modifications of a simple model originally introduced by [1] that allow us to calculate bounding values of the 802.11a ACI, which can be used in link budget calculations. Using a laboratory testbed, we verify the estimations of the model, performing experiments designed to isolate the affected 802.11 mechanisms. This isolation was enabled by not using the wireless medium, and emulating it over cables and attenuators. Our results show clear throughput degradation because of ACI in 802.11a, the magnitude of which depends on the interfering data rates, packet sizes, and utilization of the medium.

  • 8.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Sajid, Muhammad
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Siddiqui, Imran
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    A distributed, load-aware, power and frequency bargaining protocol for LTE-based networks2012Ingår i: 2012 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), Piscataway, NJ, USA: IEEE , 2012, s. 6525-6529Konferensbidrag (Refereegranskat)
    Abstract [en]

    A distributed, load-aware, joint power and frequency allocation protocol is introduced for LTE-based cellular networks, and system-level simulations are performed. Our proposed scheme aims to cooperatively limit the impact of Fractional Frequency Reuse (FFR) on the center users throughput compared to the Reuse 1 scheme, while providing sufficient throughput for the edge users. This is achieved through an asynchronous, lightweight scheme of local message exchange between neighboring LTE eNodeBs. The proposed scheme facilitates a type of "bargain" where an overloaded sector requests permission to utilize its neighbors edge bands for its center users at a limited set of transmit power levels. Grants are generated at each neighbor by solving a small-scale optimization problem. Using an LTE simulator we evaluate our scheme on a network with 21 sectors of varying load patterns. The proposed schemes performance for center users is consistently improved with respect to FFR-3, while for edge users the performance degradation is controlled by a parameter we set in the optimization problems definitions; compared to Reuse 1 edge users still have gains. Specifically, we observed up to a 46% gain in the sectors center throughput with a cost below 9% at the edges when compared to the classic FFR scheme, while the overall system throughput goes up by up to 26% in heavily loaded scenarios.

  • 9.
    Avgouleas, Ioannis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Angelakis, Vangelis
    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.
    Utilizing multiple full-duplex relays in wireless systems with multiple packet reception2014Ingår i: 2014 IEEE 19th International Workshop on Computer Aided Modeling and Design of Communication Links and Networks (CAMAD), IEEE, 2014, s. 193-197Konferensbidrag (Refereegranskat)
    Abstract [en]

    Relay nodes with physical layer cooperation have been used extensively to assist users' transmissions in wireless networks. This network level cooperation has been lately been gaining popularity and analytical expressions of the performance of a network with up to two relay nodes exist in recent literature. In this work, we give simulation results outlining the potential network level benefits of using multiple full-duplex relay nodes. We examine configurations where multiple full-duplex transceivers offer consistent improvement and provide guidelines on using them different network conditions.

  • 10.
    Avgouleas, Ioannis
    et al.
    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.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Cooperative Wireless Networking with Probabilistic On/Off Relaying2015Ingår i: 2015 IEEE 81ST VEHICULAR TECHNOLOGY CONFERENCE (VTC SPRING), IEEE , 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this work, we investigate the operation of energy efficient relay nodes assisting the transmission of packets from a number of users to a destination node. We study the impact of switching randomly a fraction of the relays on and off to the aggregate throughput, the average queue size and delay per packet of systems with relays transmitting in either Full-or Half-Duplex mode and under different channel transmissions characteristics. Furthermore, we prove analytically and illustrate via simulation means how these network metrics are affected.

  • 11.
    Avgouleas, Ioannis
    et al.
    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.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Scheduling Services on an IoT Device Under Time-Weighted Pricing2017Ingår i: Conference Proceedings IEEE 28th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC): Workshop on "Communications for Networked Smart Cities", IEEE conference proceedings, 2017, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    The emerging vision of smart cities necessitates the use of Internet of Things (IoT) network devices to implement sustainable solutions that will improve the operations of urban areas. A massive amount of smart cities services may demand allocation of computational resources, such as processing power or storage, that IoT devices offer. Within this context, we present an IoT network device comprising interfaces with one specific computational resource available. The efficient utilization of available IoT resources would improve the Quality of Service (QoS) of the IoT network that serves the smart city. All resource allocations must be completed within a given scheduling window and every service is parametrized by a pricing weight function to indicate its tolerance to be served at the beginning of the scheduling window. We propose a mathematical optimization formulation to minimize the total cost of allocating all demands within the scheduling window considering the tolerance level of each service at the same time. Moreover, we prove that the problem is computationally hard and we provide numerical results to gain insight into the impact of different pricing weight functions on the allocations’ distribution within the scheduling window.

  • 12.
    Avgouleas, Ioannis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    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.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Virtual Network Functions Scheduling under Delay-Weighted Pricing2019Ingår i: IEEE Networking Letters, E-ISSN 2576-3156, s. 1-1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider a cost minimization problem for High Volume Servers (HVS) equipped with Virtual Machines (VMs) to serve Virtual Network Functions (VNF) demands for resources. Given a scheduling period, a central scheduler decides which VM to use for each VNF demand. Each VM can be activated or disabled with different costs. Each VNF has a delay-weighted pricing function to indicate its completion time tolerance. We prove the NP-completeness of the problem and develop an algorithm based on Lagrangian relaxation and subgradient optimization to deal with this computational complexity. Finally, our numerical results demonstrate our algorithm’s effectiveness compared to two benchmarks.

  • 13.
    Elshatshat, Mohamed A.
    et al.
    Institute of Computer Science - Foundation for Research and Technology - Hellas (ICS-FORTH), Greece.
    Papadakis, Stefanos
    Institute of Computer Science - Foundation for Research and Technology - Hellas (ICS-FORTH), Greece.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Improving the Spectral Efficiency in Dense Heterogeneous Networks Using D2D-Assisted eICIC2018Ingår i: 2018 IEEE 23rd International Workshop on Computer Aided Modeling and Design of Communication Links and Networks (CAMAD), Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 32-37Konferensbidrag (Refereegranskat)
    Abstract [en]

    Heterogeneous networks (HetNets) that consist of macro base stations (MBSs) and small base stations (SBSs) are a key architectural drive for achieving the high spectral efficiency (SE) in 5G and beyond. Moreover, device-to-device (D2D) communications underlaying mobile networks can provide reliable communications and add SE gains. A major challenge in HetNets is the inter-cell interference (ICI) due to the coexistence of multiple tiers of base stations (BSs). To tackle this challenge, the enhanced inter-cell interference coordination (eICIC) scheme was adopted by 3GPP. In eICIC the MBSs mute their transmission during the so-called ᅵalmost blank subframesᅵ (ABS). This muting strategy causes resources reduction to the MBS users (MUEs). We propose the use of D2D communications to forward the transmission from the SBS to the MUEs during ABS subframes, by using inactive UEs to relay the downlink transmission, when the destination UEs are outside the coverage of the BS. We use a heuristic resource allocation (RA) algorithm based on the traffic load at the SBSs that integrates eICIC with D2D communications to avoid the service degradation during the time-domain muting. Simulation results of a HetNet with D2D-eICIC show that the SE of our approach outperforms other interference management approaches.

  • 14.
    Fowler, Scott
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Sarfraz, Jalal
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Abbas, M. Muddassir
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Bergfeldt, Erik
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Evaluation and prospects from a measurement campaign on real multimedia traffic in LTE vs. UMTS2014Ingår i: Wireless Communications, Vehicular Technology, Information Theory and Aerospace Electronic Systems (VITAE'14), IEEE 4th International Conference on, IEEE Press, 2014, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    The LTE standard has been developed for high-bandwidth mobile access for today’s data-heavy applications. With broadband cellular available already from the UMTS system, users are expecting the LTE network to provide high quality communication. To ensure the quality and correctness of complex systems of LTE, it is important to evaluate the behavior of traffic on a LTE network in relation to UMTS. In this paper, LTE and UMTS measurements on video traffic were performed in a real environment, allowing for greater development, and understanding of network traffic performance.

  • 15.
    Fowler, Scott
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Sarfraz, Jalal
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Abbas, Muhammad Muddassir
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Gaussian semi-Markov Model based on Real Video Multimedia Traffic2015Ingår i: IEEE International Conference on Communications Communications (ICC) 2015 / [ed] IEEE, IEEE Press, 2015, s. 6971-6976Konferensbidrag (Refereegranskat)
    Abstract [en]

    The 3rd Generation Partnership Project (3GPP) introduced the new radio access technology, LTE (Long Term Evolution) and LTE-Advanced, which has the capability to provide larger bandwidth and low latencies on a wireless network in order to fulfill the demand of Users' Equipment (UEs) with acceptable Quality of Service (QoS). One of the data-heavy applications that has exploded on the market is Video. This calls for accurate modeling of video traffic. To ensure the quality and correctness of complex systems with Video traffic, it is important to evaluate the behavior of the traffic in the heterogeneous environment. This paper presents measurements on LTE Video traffic which were performed in a real environment. We derived a semi-Markov model which accurately reproduces the statistics of composite Video measurements over LTE network.

  • 16.
    Fragkiadakis, Alexandros
    et al.
    Fdn Research and Technology Hellas, Greece .
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Tragos, Elias Z.
    Fdn Research and Technology Hellas, Greece .
    Securing Cognitive Wireless Sensor Networks: A Survey2014Ingår i: International Journal of Distributed Sensor Networks, ISSN 1550-1329, E-ISSN 1550-1477, nr 393248Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Wireless sensor networks (WSNs) have gained a lot of attention recently due to the potential they provide for developing a plethora of cost-efficient applications. Although research on WSNs has been performed for more than a decade, only recently has the explosion of their potential applicability been identified. However, due to the fact that the wireless spectrum becomes congested in the unlicensed bands, there is a need for a next generation of WSNs, utilizing the advantages of cognitive radio (CR) technology for identifying and accessing the free spectrum bands. Thus, the next generation of wireless sensor networks is the cognitive wireless sensor networks (CWSNs). For the successful adoption of CWSNs, they have to be trustworthy and secure. Although the concept of CWSNs is quite new, a lot of work in the area of security and privacy has been done until now, and this work attempts to present an overview of the most important works for securing the CWSNs. Moreover, a discussion regarding open research issues is also given in the end of this work.

  • 17.
    He, Qing
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Ephremides, Anthony
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan. Department of Electrical and Computer Engineering, University of Maryland, USA.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan. Department of Electrical and Computer Engineering, University of Maryland, USA.
    Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks2016Ingår i: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 3, nr 3, s. 322-331Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

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

  • 18.
    He, Qing
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Ephremides, Anthony
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan. Department of Electrical and Computer Engineering, University of Maryland, USA.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Revisiting Minimum-Length Scheduling in Wireless Networks: An Algorithmic Framework2012Ingår i: International Symposium on Information Theory and its Applications (ISITA), 2012, Piscataway, NJ, USA: IEEE , 2012, s. 506-510Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 19.
    Kosta, Antzela
    et al.
    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.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Age of Information: A New Concept, Metric, and Tool2017Bok (Refereegranskat)
    Abstract [en]

    In an increasingly networked world in which information is becoming increasingly actual, how can a system know with certainty just how fresh the information on a remote system is? Much work has been done on delay or latency in systems, but only recently has the concept of the freshness of information in or about a system become quantifiable. This is termed the Age of Information.

    Age of Information provides a whole new set of metrics and tools that can be used to characterize the freshness of information in communications, control and, indeed, information systems. In its early development, this monograph provides the reader with an easy-to-read tutorial-like introduction into this novel approach of dealing with information within systems. A critical summary of the work to date details the concept for the reader. A description of the fundamentals of the performance metrics is then presented before showing how the approach can be used as a tool in improving metrics in other contexts.

    The survey and tutorial nature of this monograph will save any researcher or student considerable time in understanding the basics of Age of Information, which is destined to become an important research topic in networked systems.

  • 20.
    Kosta, Antzela
    et al.
    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.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Age of Information: A New Concept, Metric, and Tool2017Ingår i: Foundations and Trends in Networking, ISSN 1554-057X, Vol. 12, nr 3, s. 162-259Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Age of information (AoI) was introduced in the early 2010s as a notion to characterize the freshness of the knowledge a system has about a process observed remotely. AoI was shown to be a fundamentally novel metric of timeliness, significantly different, to existing ones such as delay and latency. The importance of such a tool is paramount, especially in contexts other than transport of information, since communication takes place also to control, or to compute, or to infer, and not just to reproduce messages of a source. This volume comes to present and discuss the first body of works on AoI and discuss future directions that could yield more challenging and interesting research.

  • 21.
    Kosta, Antzela
    et al.
    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.
    Ephremides, Anthony
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Age of Information and Throughput in a Shared Access Network with Heterogeneous Traffic2018Ingår i: IEEE Global Telecommunications Conference (GLOBECOM), 2018, pp. 1-6., 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider a cognitive shared access scheme consisting of a high priority primary node and a low priority network with N secondary nodes accessing the spectrum. Assuming bursty traffic at the primary node, saturated queues at the secondary nodes, and multipacket reception capabilities at the receivers, we derive analytical expressions of the time average age of information of the primary node and the throughput of the secondary nodes. We formulate two optimization problems, the first aiming to minimize the time average age of information of the primary node subject to an aggregate secondary throughput requirement. The second problem aims to maximize the aggregate secondary throughput of the network subject to a maximum time average staleness constraint. Our results provide guidelines for the design of a multiple access system with multipacket reception capabilities that fulfills both timeliness and throughput requirements.

  • 22.
    Lei, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Performance analysis of chunk-based resource allocation in wireless OFDMA systems2012Ingår i: Proceedings from the 17th IEEE International Workshop on Computer Aided Modeling and Design of Communication Links and Networks (CAMAD), September 17-19, 2012, Barcelona, Spain, IEEE , 2012, s. 90-94Konferensbidrag (Refereegranskat)
    Abstract [en]

    In typical resource allocation for Orthogonal Frequency Division Multiple Access (OFDMA), assigning subcarriers to the more favorable users provides beneficial diversity and increased system performance. It is however relevant to consider OFDMA resource allocation with a subcarrier adjacency restriction, grouping a number of adjacent subcarriers into a chunk, both for physical design simplicity and for complexity mitigation. In this paper, we classify different resource allocation policies for chunk-based allocation. We investigate how to optimally allocate resources by using discrete rates and discrete power levels. This is enabled by developing binary integer optimization models to obtain the optimal solution for this comparative study. We present numerical results to evaluate the performance of different resource allocation policies under different parameters and scenarios.

  • 23.
    Li, Yuan
    et al.
    School of Computer, National University of Defense Technology, China.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pioro, Michal
    Institute of Telecommunications, Warsaw University of Technology, Poland.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    On the Resilient Network Design of Free Space Optical Wireless Network for Cellular Backhauling2016Ingår i: Optical Wireless Communications / [ed] Murat Uysal, Carlo Capsoni, Zabih Ghassemlooy, Anthony Boucouvalas, Eszter Udvary, Springer, 2016, s. 485-510Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    With the densification of nodes in cellular networks, free space optics (FSO) connections are becoming an appealing low cost and high rate alternative to copper and fiber backhaul solutions for wireless communication systems. To en- sure a reliable cellular backhaul, provisions for redundant, disjoint paths between the nodes must be made in the design phase. This chapter aims at finding a cost- effective solution to upgrade the cellular backhaul with pre-deployed optical fibers using FSO links and mirror components. A novel integer linear programming model to approach optimal FSO backhaul design, guaranteeing K-disjoint paths connecting each node pair is presented. Next, a column generation method to a path-oriented mathematical formulation is developed. Applying the method in a sequential man- ner enables high computational scalability. Realistic scenarios are used to demon- strate the proposed approaches which efficiently provide optimal or near-optimal solutions, and thereby allow for accurately dealing with the trade-off between cost and reliability. 

  • 24.
    Li, Yuan
    et al.
    Lund University, Sweden.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pioro, Michal
    Lund University, Sweden; Warsaw University of Technology, Poland.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten. University of Maryland, MD 20742 USA.
    Optimization of Free Space Optical Wireless Network for Cellular Backhauling2015Ingår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 33, nr 9, s. 1841-1854Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With the densification of nodes in cellular networks, free space optic (FSO) connections are becoming an appealing low cost and high rate alternative to copper and fiber backhaul solutions for wireless communication systems. To ensure a reliable cellular backhaul, provisions for redundant disjoint paths between the nodes must be made in the design phase. This paper aims at finding a cost-effective solution to upgrade the cellular backhaul with pre-deployed optical fibers using FSO links and mirror components. Since the quality of the FSO links depends on several factors, such as transmission distance, power, and weather conditions, we adopt an elaborate formulation to calculate link reliability. We present a novel integer linear programming model to approach optimal FSO backhaul design, guaranteeing K-disjoint paths connecting each node pair. Next, we derive a column generation method to a path-oriented mathematical formulation. Applying the method in a sequential manner enables high computational scalability. We use realistic scenarios to demonstrate that our approaches efficiently provide optimal or near-optimal solutions, and thereby allow for accurately dealing with the trade-off between cost and reliability.

  • 25.
    Li, Yuan
    et al.
    Department of Electrical and Information Technology, Lund University, Lund, Sweden .
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pioro, Michał
    Institute of Telecommunications, Warsaw University of Technology, Warsaw, Poland.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Resilient topology design for free space optical cellular backhaul networking2014Ingår i: 2014 IEEE Globecom Workshops (GC Wkshps), IEEE Press, 2014, s. 487-492Konferensbidrag (Refereegranskat)
    Abstract [en]

    With cellular networks' densification, backhaul solutions tend to go wireless to reduce costs. Free space optic (FSO) links are becoming an appealing, secure and high rate alternative to RF. To ensure a reliable cellular backhaul, redundancy provisions for disjoint paths between the nodes must be made in the network design phase. This paper presents cost-effective solutions, using FSO links and mirrors, that can be employed to upgrade a cellular backhaul with pre-deployed optical fibers. An integer programming model is introduced to approach optimal FSO backhaul design, guaranteeing K-disjoint paths between each node pair. We use realistic scenarios to demonstrate some optimal backhaul topologies by solving the model. We also illustrate the impact of K and the number of optical fibers on optimal solutions.

  • 26.
    Li, Yuan
    et al.
    Lund University, Sweden.
    Pioro, Michal
    Lund University, Sweden; Warsaw University of Technology, Poland.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Fragkiadakis, Alexandros
    Fdn Research and Technology Hellas FORTH ICS, Greece.
    Mathematical modelling of metric-driven routing and resource allocation in wireless mesh networks2014Ingår i: 2014 16TH INTERNATIONAL TELECOMMUNICATIONS NETWORK STRATEGY AND PLANNING SYMPOSIUM (NETWORKS), IEEE , 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    The traditional routing protocols used in wireless mesh networks like AODV are not very efficient since the number of hops to a destination is mainly considered as the routing metric. This may lead to shorter paths; however, the throughput can decrease when traffic is routed through those paths. Various contributions have proposed different metrics or completely different routing algorithms. Nevertheless, for many of these metrics, real-time network performance monitoring is required, increasing their overhead, while the implementation of many of the proposed routing protocols is not feasible in practice because of their complexity. In this paper, we aim to optimize link metrics together with routing. We preserve the shortest path routing principle but with optimizing the link metrics; thus, combining the shortest path algorithms low overhead with an optimized link metrics scheme. We present a two-phase scheme for the considered problem. During the first phase, we seek for the optimal link scheduling for minimizing the required time slots and then, in the second phase, we present a mixed integer programming model for metric-driven routing design. For comparison, we also present the optimization models for global optimized routing and shortest-hop routing, providing numerical results.

  • 27.
    Lundgren, Magnus
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan. Huazhong University of Science and Technology, Peoples R China.
    Helgesson, Dan
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan. Huazhong University of Science and Technology, Peoples R China.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Ge, Xiaohu
    Huazhong University of Science and Technology, Peoples R China.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Energy Aware Rate Selection in Cognitive Radio Inspired Wireless Smart Objects2014Ingår i: 2014 IEEE SYMPOSIUM ON COMPUTERS AND COMMUNICATION (ISCC), IEEE , 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    The spectrum overcrowding drives investigating solutions to increase the usage of underutilized spectrum bands, minimize redundant interference and maximize expected throughput. Cognitive radio (CR) has presented itself as an appealing technology for solutions in energy constrained devices. Within this context, this paper introduces a system structure which enhances wireless multi-interfaced objects with cognitive radio. We propose a modular architecture to imbue such multi-interfaced devices with cognitive radio features, and based on it we present numerical results which identify performance boundaries and potential energy savings for an adaptive uncoded modulation scheme. Our results show that the tradeoff between throughput and energy consumption can be leveraged satisfactorily to enhance the lifetime significantly in noisy environments.

  • 28.
    Matinrad, Niki
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Andersson Granberg, Tobias
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Ennab Vogel, Nicklas
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för hälso- och sjukvårdsanalys. Linköpings universitet, Medicinska fakulteten.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Optimal Dispatch of Volunteers to Out-of-hospital Cardiac Arrest Patients2019Ingår i: Proceedings of the 52nd Hawaii InternationalConference on System Sciences (HICSS), Hawaii, USA, 8th-11th January 2019, University of Hawai'i at Manoa , 2019, s. 4088-4097Konferensbidrag (Refereegranskat)
    Abstract [en]

    Initiatives with mobile phone dispatched volunteers to out-of-hospital cardiac arrest (OHCA) cases, can be found today in some countries, e.g. Sweden, the Netherlands, Switzerland and Italy. When an OHCA case is reported, an alarm is sent to the registered volunteers’ phones. However, the allocation of which volunteers to send to the automatic external defibrillator (AED) and who to send directly to the patient, is today based on simple rules of thumb. In this paper, we propose a model to optimally select how many and which volunteers to send directly to the patient, and who should pick up and deliver an AED. The results show that the model can help increase the survivability of the patients, compared to simple decision rules.

  • 29.
    Mohapatra, Parthajit
    et al.
    G. S. Sanyal School of Telecommunications, Indian Institute of Technology, Kharagpur, India.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Lee, Jemin
    Department of Information and Communication Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Korea.
    Quek, Tony Q.S.
    Information Systems Technology and Design Pillar, Singapore University of Technology and Design, Singapore.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Secure Communications for the Two-user Broadcast Channel with Random Traffic2018Ingår i: IEEE Transactions on Information Forensics and Security, ISSN 1556-6013, E-ISSN 1556-6021, Vol. 13, nr 9, s. 2294-2309Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, we study the stability region of the two-user broadcast channel (BC) with bursty data arrivals and security constraints. It is assumed that one of the receivers has a secrecy constraint, i.e., its packets need to be kept secret from the other receiver, which is defined based on SINR. The receiver with secrecy constraint has full-duplex capability to send a jamming signal for improving its service rate. The stability region of the two-user BC with secrecy constraint is characterized for the general decoding case. Then, assuming two different decoding schemes the respective stability regions are derived. The fullduplex operation of receiver results in self-interference, and the effect of imperfect self-interference cancelation on the stability region is also investigated. The stability region of the BC with a secrecy constraint, where the receivers do not have full duplex capability can be obtained as a special case of the results derived in this paper. In addition, the paper considers the problem of maximizing the saturated throughput of the queue for which there is no secrecy constraint under minimum service guarantees for the other queue. The results provide new insights on the effect of the secrecy constraint on the stability region of the BC. It is found that the stability region with secrecy constraint is sensitive to the degree of self-interference cancelation.

  • 30.
    Papadimitriou, Georgios
    et al.
    Ericsson, Sweden.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Traganitis, Apostolos
    University of Crete, Greece.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Network-level performance evaluation of a two-relay cooperative random access wireless system2015Ingår i: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 88, s. 187-201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In wireless networks relay nodes can be used to assist the users transmissions to reach their destination. Work on relay cooperation, from a physical layer perspective, has up to now yielded well-known results. This paper takes a different stance focusing on network-level cooperation. Extending previous results for a single relay, we investigate here the benefits from the deployment of a second one. We assume that the two relays do not generate packets of their own and the system employs random access to the medium; we further consider slotted time and that the users have saturated queues. We obtain analytical expressions for the arrival and service rates of the queues of the two relays and the stability conditions. We investigate a model of the system, in which the users are divided into clusters, each being served by one relay, and show its advantages in terms of aggregate and throughput per user. We quantify the above, analytically for the case of the collision channel and through simulations for the case of multi-packet reception (MPR), and we provide insight on when the deployment of a second relay in the system can yield significant advantages.

  • 31.
    Papadopoulos, Georgios Z.
    et al.
    ICube Laboratory, University of Strasbourg, France.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Gallais, Antoine
    ICube Laboratory, University of Strasbourg, France.
    Noel, Thomas
    ICube Laboratory, University of Strasbourg, France.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Distributed adaptive scheme for reliable data collection in fault tolerant WSNs2015Ingår i: Internet of Things (WF-IoT), 2015 IEEE 2nd World Forum on, Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 116-121Konferensbidrag (Refereegranskat)
    Abstract [en]

    Reliable data packet transfer is an essential facet of quality of service in Wireless Sensor Networks (WSNs). WSNs require pertinent and reliable data collection schemes to provide dependable information. We analyze the factors that affect reliability, and design efficient combinations of the possible options. While many researchers have tackled this issue by focusing on particular layers of the embedded communication stack (e.g., Medium Access Control (MAC) or routing layer), we propose a layer-independent transmission rate adaptive scheme, where no additional control messages are required. We focus on packet loss avoidance along prone-to-failure paths to the sink with the main objective being the efficient queue management of a sensor node. Based on certain factors (e.g., application or queue requirements) nodes will consequently take adjustment decisions. Our thorough simulation experiments demonstrate that DRAS reduces the packet drops and improves the data collection procedure in an energy efficient manner.

  • 32.
    Pappas, Nikolaos
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Gunnarsson, Johan
    Linköpings universitet, Institutionen för beteendevetenskap och lärande. Linköpings universitet, Filosofiska fakulteten.
    Kratz, Ludvig
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Kountouris, Marios
    Huawei Technology Co Ltd, Peoples R China.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Age of Information of Multiple Sources with Queue Management2015Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2015, s. 5935-5940Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider a system of multiple sources generating status update packets, which need to be sent by a single transmitter to a destination over a network. In the model we study, the packet generation time may vary at each source, and the packets go through the network with a random delay. Each update carries a time stamp of its generation, allowing the destination to calculate for each source the so called Age of Information, which measures the timeliness of each status update arriving. Considering that queuing delay can unnecessarily increase the age of a critical status update, we propose here a queue management technique, in which we maintain a queue with only the latest status packet of each source, overwriting any previously queued update from that source. This simple technique drastically limits the need for buffering and can be applied in systems where the history of source status is not relevant. We show that this scheme results in significantly less transmissions compared to the standard M/M/1 queue model. Furthermore, the proposed technique reduces the per source age of information, especially in settings not using queue management with high status update generation rates.

  • 33.
    Pöhls, Henrich C.
    et al.
    University of Passau, Germany.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Suppan, Santiago
    Siemens AG, CT RTC ITS, Germany.
    Fischer, Kai
    Siemens AG, CT RTC ITS, Germany.
    Oikonomou, George
    Faculty of Engineering, University of Bristol, UK.
    Tragos, Elias Z.
    FORTH-ICS, Greece.
    Rodriguez, Rodrigo Diaz
    Atos, Spain.
    Mouroutis, Theodoros
    Cyta Hellas, Greece.
    RERUM: Building a reliable IoT upon privacy- and security- enabled smart objects2014Ingår i: 2014 IEEE Wireless Communications and Networking Conference Workshops (WCNCW), Institute of Electrical and Electronics Engineers (IEEE), 2014, s. 122-127Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Internet of Things (IoT) provides a platform for the interconnection of a plethora of smart objects. It has been widely accepted for providing Information and Communication Technologies (ICT) applications in many ᅵsmartᅵ environments, such as cities, buildings, metering, and even agriculture. For several reasons though such applications have yet to achieve wide adoption; a major hurdle is the lack of user trust in the IoT and its role in everyday activities. RERUM, a recently started FP7 European Union project. aims to develop a framework which will allow IoT applications to consider security and privacy mechanisms early in their design phase, ensuring a configurable balance between reliability (requiring secure, trustworthy and precise data) and privacy (requiring data minimization for private information, like location). The RERUM framework will comprise an architecture, built upon novel network protocols and interfaces as well as the design of smart objects hardware. To highlight the challenges and evaluate the framework, RERUM will employ several Smart City application scenarios, which will be deployed and evaluated in real-world testbeds in two Smart Cities participating in the project. Here we detail the key technologies RERUM will investigate over the coming three years to reach its vision for IoT security, privacy and trust.

  • 34.
    Tragos, Elias Z.
    et al.
    Institute of Computer Science, Foundation for Research and Technology Hellas, Greece.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Cognitive radio inspired M2M communications2013Ingår i: 2013 16th International Symposium on Wireless Personal Multimedia Communications (WPMC), Institute of Electrical and Electronics Engineers (IEEE), 2013, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Internet of Things (IoT) presents itself as one of the basic pillars of the Future Internet. Such an extended network of heterogeneous ᅵthingsᅵ forms a global network infrastructure supported by several communication protocols where physical and virtual objects are interconnected. It is envisaged that billions of machines will be connected to the Internet, pushing the current communication technologies to their limits in terms of connectivity and performance. The wireless interconnectivity of a large number of devices in the ISM bands is a fundamental issue due to the resulting high interference environment, which degrades severely the performance and the connectivity of these devices. The Cognitive Radio technology can help mitigate the interference effect in such environments, employing smart techniques for accessing the wireless spectrum in an opportunistic manner. This paper discusses the adaptation of Cognitive Radio technology for enhancing the machine-to-machine communications, presenting the challenges and open issues for future research.

  • 35.
    Tragos, E.Z.
    et al.
    FORTH-ICS, Greece.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Fragkiadakis, A.
    Siemens SRL, Romania.
    Gundlegard, D.
    Faculty of Engineering, University of of Bristol, United Kingdom.
    Nechifor, C.-S.
    University of of Passau, Germany.
    Oikonomou, G.
    Eurescom, Germany.
    Pohls, H.C.
    FORTH-ICS, Greece.
    Gavras, A.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Enabling reliable and secure IoT-based smart city applications2014Ingår i: 2014 IEEE International Conference on Pervasive Computing and Communication Workshops, PERCOM WORKSHOPS 2014, IEEE Computer Society, 2014, nr 6815175, s. 111-116Konferensbidrag (Refereegranskat)
    Abstract [en]

    Smart Cities are considered recently as a promising solution for providing efficient services to citizens with the use of Information and Communication Technologies. With the latest advances on the Internet of Things, a new era has emerged in the Smart City domain, opening new opportunities for the development of efficient and low-cost applications that aim to improve the Quality of Life in cities. Although there is much research in this area, which has resulted in the development of many commercial products, significant parameters like reliability, security and privacy have not been considered as very important up until now. The newly launched FP7-SmartCities-2013 project RERUM aims to build upon the advances in the area of Internet of Things in Smart Cities and develop a framework to enhance reliability and security of smart city applications, with the citizen at the center of attention. This work presents four applications that will be developed within RERUM, gives a general description of the open reliability and security issues that have to be taken into account and gives an overall view of the solutions that RERUM will develop to address these issues. © 2014 IEEE.

  • 36.
    Yuan, Di
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Chen, Lei
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Karipidis, Eleftherios
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    On Optimal Link Activation with Interference Cancelation in Wireless Networking2013Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 62, nr 2, s. 939-945Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A fundamental aspect in performance engineering of wireless networks is optimizing the set of links that can be concurrently activated to meet given signal-to-interference-and-noise ratio (SINR) thresholds. The solution of this combinatorial problem is the key element in scheduling and cross-layer resource management. In this paper, we assume multiuser decoding receivers, which can cancel strongly interfering signals. As a result, in contrast to classical spatial reuse, links being close to each other are more likely to be active concurrently. Our focus is to gauge the gain of successive interference cancellation (SIC), as well as the simpler, yet instructive, case of parallel interference cancellation (PIC), in the context of optimal link activation. We show that both problems are NP-hard and develop compact integer linear programming formulations that enable to approach global optimality. We provide an extensive numerical performance evaluation, indicating that for low to medium SINR thresholds the improvement is quite substantial, especially with SIC, whereas for high SINR thresholds the improvement diminishes and both schemes perform equally well.

  • 37.
    Yuan, Di
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Lei, Lei
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Minimum-Length Scheduling in Wireless Networks with Multi-User Detection and Interference Cancellation: Optimization and Performance Evaluation2012Ingår i: IEEE International Conference on Communication Systems (ICCS), 2012, Piscataway, NJ, USA: IEEE , 2012, s. 315-319Konferensbidrag (Refereegranskat)
    Abstract [en]

    Minimum-length scheduling has been a subject of extensive research in performance engineering of wireless ad hoc networks. We consider the problem under the unconventional setting of multi-user detection receivers that can perform decoding successively, potentially admitting interference cancellation. Thus, in contrast to classical spatial reuse, strong interference is not necessarily harmful. The paper studies fundamental aspects of assessing the achievable performance by successive decoding and interference cancellation versus that of the conventional setup. Computationally, the task is very challenging - the optimal decoding pattern is intertwined with the composition of time slots. We provide structural results of the problem, and develop integer programming formulations enabling to effectively determine the optimal schedule. Computational experiments are provided to shed light on the achievable performance gain of successive decoding with interference cancellation for minimum-length scheduling.

  • 38.
    Zhao, Chao
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Timus, Bogdan
    Ericsson Research, Kista, Sweden.
    Evaluation of Cell Selection Algorithms in LTE-Advanced Relay Networks2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    The concept of relay has been introduced in LTE-Advanced as a promising approach to enhance network performance. Because of the diversity introduced by deploying relays to a purely macro network, the conventional cell selection schemes do not perform well, leading to noticeable throughput degradation for some of the users. An algorithm attempting to address the issue is the use of data rate mapped from Reference Signal Received Power (RSRP) as the cell selection criterion. This algorithm, however, introduces an extra interference problem. We therefore describe an additional interference avoidance (IA) mechanism to enhance it. Performance evaluation and analysis are carried out to gain insights on the enhanced algorithm and two additional algorithms, both developed in this paper, to demonstrate their effectiveness in improving the throughput. Simulation results show that for relay-enabled networks the new algorithms based on data rates obtained directly from RSRP and the Reference Signal Received Quality (RSRQ) outperform the algorithm based on RSRP with offset. Moreover, the interference issue is well dealt with via the implementation of additional IA.

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