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  • 1.
    Bayer, Nico
    et al.
    Deutsche Telekom/T-Systems, Darmstadt, Germany.
    Cavalcanti de Castro, Marcel
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Koucheryavy, Yevgeni
    Tampere University of Technolo, Finland.
    Mitoraj, Piotr
    Tampere University of Technology, Finland.
    Staehle, Dirk
    University of Würzburg, Germany.
    VoIP service performance optimization in pre-IEEE 802.11s Wireless Mesh Networks2008In: Proceedings of the IEEE International Conference on Circuits andSystems for Communications (ICCSC) 2008, IEEE conference proceedings, 2008, p. 75-79Conference paper (Refereed)
    Abstract [en]

    802.11-based wireless mesh networks are seen as a means for providing last mile connections to next generation networks. Due to the low deployment cost and the mature technology used, they are scalable, easy to implement and robust. With an increasing coverage of wireless networks, VoIP becomes a cheaper alternative for traditional and cellular telephony. In this paper, we carry out a feasibility study of VoIP in a dual radio mesh environment. Heading towards 802.11s, we present the design of a mesh testbed and methodology for performing the measurements. Additionally, we address the problem that small voice packets introduce a high overhead leading to a low voice capacity of 802.11 based mesh networks. In order to alleviate this problem and increase the voice capacity, a novel packet aggregation mechanism is presented and evaluated using the ns-2 simulator.

  • 2. Brolin, Jonas
    et al.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Hedegren, Mikael
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Implementing Packet Aggregation in the Linux Kernel2008Conference paper (Refereed)
    Abstract [en]

    In multi-hop wireless mesh networks (WMN) Voice over IP (VoIP) suffers from large overhead created by the IP/UDP/RTP/MAC header and time due to collisions. As a result the VoIP capacity of WMNs is small. As shown in [1] a 3 hop WMN at a data rate of 2Mbit/s can only support 3 concurrent VoIP flows. [1], [2] and [3] propose the use of packet aggregation in order to reduce the overhead and thus increase the capacity. The idea behind packet aggregation is to combine multiple small packets into a single larger one, reducing overhead and collision probability in multi-hop environment. This paper presents insights into an implementation of an aggregation scheme in the Linux Kernel and its experimental evaluation

  • 3.
    Brunström, Anna
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Cavalcanti de Castro, Marcel
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Lavén, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Galluccio, L
    NEWCOM++ DR11.3: Final report on the activities and results of WPR112010Report (Other academic)
    Abstract [en]

    This document is the last deliverable of WPR.11 and presents an overview of the final activities carried out within the NEWCOM++ Workpackage WPR.11 during the last 18 months. We provide a description of the most consolidated Joint Research Activities (JRAs) and the main results so far obtained. We also address some considerations on the future activities which are expected to continue at the end of NEWCOM++

  • 4.
    Castro, Marcel C.
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Vaidya, Nitin H.
    QoS-Aware Channel Scheduling for Multi-Radio/Multi-Channel Wireless Mesh Networks2009In: Proceedings of the Fourth ACM International Workshop on Wireless Network Testbeds, Experimental evaluation and Characterization (WiNTECH 09), New York: ACM , 2009Conference paper (Refereed)
    Abstract [en]

    In non-static multi-radio/multi-channel wireless mesh networks architectures such as Net-X, mesh nodes need to switch channels in order to communicate with different neighbors. Present channel schedulers do not consider the requirements of real time traffic such as voice over IP. Thus the resulting quality is low. We propose a novel channel scheduler for the Net-X platform that takes into account packet priorities. We evaluate the algorithm on the KAUMesh testbed. Our algorithm outperforms the standard round-robin scheduler both in terms of average delay and jitter.

  • 5.
    Cavalcanti de Castro, Marcel
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Karlsson, Jonas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Capacity Increase for Voice over IP Traffic through Packet Aggregation in Wireless Multihop Mesh Networks2007Conference paper (Refereed)
    Abstract [en]

    Recently, Voice over IP (VoIP) has become an important service for the future internet. However, for ubiquitous wireless VoIP services, greater coverage will be necessary as promised by the advent of e.g. 802.11 WLAN based wireless meshed networks. Unfortunately, the transmission of small (voice) packets imposes high overhead which leads to low capacity for VoIP over 802.11 based multihop meshed networks. In this work, we present a novel packet aggregation mechanism that significantly enhances capacity of VoIP in wireless meshed networks while still maintaining satisfactory voice quality. Extensive experiments using network simulation ns-2 confirm that our packet aggregation algorithm can lead to a significantly increase in the number of supported concurrent VoIP flows over a variety of different hop numbers while reducing the MAC layer contention

  • 6.
    Chow, Lawrence
    et al.
    Stanford Univ, Stanford, CA 94305 USA.
    Collins, Bradley
    Stanford Univ, Stanford, CA 94305 USA.
    Bambos, Nicholas
    Stanford Univ, Stanford, CA 94305 USA.
    Dely, Peter
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Peylo, Christoph
    Deutsch Telekom Labs, Berlin, Germany.
    Einsiedler, Hans
    Deutsch Telekom Labs, Berlin, Germany.
    Bayer, Nico
    Deutsch Telekom Labs, Berlin, Germany.
    Channel Aware Rebuffering for Wireless Media Streaming with Handoff Control2013In: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), IEEE Press, 2013, p. 4434-4439Conference paper (Refereed)
    Abstract [en]

    Packet/frame 'rebuffering' in wireless video streaming typically considers only connectivity from the mobile terminal to its network access point (AP). However, in the presence of multiple APs with the possibility of handoffs, the overall wireless environment should be considered. We develop a model capturing joint rebuffering & handoff dynamics in wireless video streaming, and design a new channel-aware joint rebuffering & handoff control scheme, aiming to minimize the long-run average cost of video jitters and freezes. We first characterize the optimal control in the general case of multiple wireless APs/channels and multiple states per channel. Subsequently, we evaluate the system performance in key important cases, using experimental traces of wireless channel data. We explore the relationship between optimal rebuffering thresholds and overall channel dynamics, and evaluate the associated joint handoff control. The performance results demonstrate the importance of jointly managing rebuffering and handoff controls to achieve high-performance wireless video streaming.

  • 7.
    Chow, Lawrence
    et al.
    Stanford University.
    Collins, Bradley
    Stanford University.
    Bambos, Nick
    Stanford University.
    Peylo, Christoph
    Telekom Innovation Laboratories.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Playout-Buffer Aware Hand-Off Control for Wireless Video Streaming2012In: 2012 IEEE Global Communications Conference (GLOBECOM 2012): Proceedings of a meeting held 3-7 December 2012, Anaheim, California, USA, IEEE conference proceedings, 2012, p. 5237-5242Conference paper (Refereed)
    Abstract [en]

    Wireless hand-off control typically considers only connectivity strength from the mobile terminal to alternative access points. In wireless video streaming, however, where video freezing must be avoided at the mobile terminal, the playout buffer level should also be considered by hand-off control. In this paper, we first develop a model capturing hand-off dynamics under video streaming, and design a new playout buffer aware hand-off control. It aims to avert a video freeze for as long as possible, maximizing the expected time until freezing. We compute the optimal control in the general case of multiple access points and multiple connectivity strength states per channel. The optimal hand-off control is then computationally probed in specific relevant cases. It is demonstrated that there is a certain playout buffer threshold level - a buffer tipping point - above which a hand-off should be attempted. Of course, this tipping point depends on the access point to mobile channel statistics

  • 8.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Architectures and Algorithms for Future Wireless Local Area Networks2012Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Future Wireless Local Area Networks (WLANs) with high carrier frequencies and wide channels need a dense deployment of Access Points (APs) to provide good performance. In densely deployed WLANs associations of stations and handovers need to be managed more intelligently than today.

    This dissertation studies when and how a station should perform a handover and to which AP from a theoretical and a practical perspective. We formulate and solve optimization problems that allow to compute the optimal AP for each station in normal WLANs and WLANs connected via a wireless mesh backhaul. Moreover, we propose to use software defined networks and the OpenFlow protocol to optimize station associations, handovers and traffic rates. Furthermore, we develop new mechanisms to estimate the quality  of a link  between a station and an AP. Those mechanisms allow optimization algorithms to make better decisions about when to initiate a handover. Since handovers in today’s WLANs are slow and may disturb real-time applications such as video streaming, a faster procedure is developed in this thesis.

    Evaluation results from wireless testbeds and network simulations show that our architectures and algorithms significantly increase the performance of WLANs, while they are backward compatible at the same time.

  • 9.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Cross-Layer Optimization of Voice over IP in Wireless Mesh Networks2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wireless Mesh Networks (WMNs) have emerged as a promising network technology, which combines the benefits of cellular networks and Wireless Local Area Networks (WLANs). In a WMN mesh routers wirelessly relay traffic on behalf of other mesh routers or clients and thereby provide coverage areas comparable to cellular networks, while having the low complexity and low costs of WLANs. As Voice over IP (VoIP) is a very important Internet service, it is critical for the success of WMNs to support high quality VoIP. However, currentWMNs are not adapted well for VoIP. The capacity and scalability of single-radio WMNs is low, especially for small packet transmissions of VoIP calls, because the MAC and PHY layer overhead for small packets is high. The scalability of multiradio/multi-channel WMNs is usually higher, since fewer nodes contend for a channel. However channel scheduling might be required, which can lead to excessive delay and jitter and result in poor VoIP quality. In this thesis we investigate how to deliver high quality VoIP in single radio and multi-radio networks by using cross-layer optimization. For single radio WMNs, we consider the use of IP packet aggregation and IEEE 802.11e transmission opportunities. We conclude that IP packet aggregation greatly improves the capacity and thereby the scalability of WMNs. We show that the key for providing good quality is to artificially delay packets prior to aggregation. We propose a distributed cross-layer optimization system, which, based on Fuzzy Logic Inference, derives an aggregation delay that enhances the capacity and quality. For multi-radio/multi-channel WMNs, we demonstrate the importance of qualityof- service-aware channel scheduling. We develop a quality-of-serviceaware channel scheduler that compared to a basic round-robin scheme significantly reduces jitter and in that way increases VoIP quality. Our analysis shows that there is a trade-off between the jitter of high priority VoIP traffic and the throughput of background TCP traffic. The proposed optimizations significantly increase the capacity of singleradio and multi-radio WMNs. This allows network operators to serve more users with an existing mesh infrastructure or provide better service delivery to existing users.

  • 10.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Towards an Architecture for OpenFlow and Wireless Mesh Networks2011Conference paper (Refereed)
  • 11.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Cavalcanti de Castro, Marcel
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Moldsvor, Arild
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Soukhakian, Sina
    Practical Considerations for Channel Assignment in Wireless Mesh Networks2010In: GLOBECOM Workshops (GC Wkshps), 2010 IEEE, IEEE , 2010, p. 763-767Conference paper (Refereed)
    Abstract [en]

    Abstract--- In multi-radio wireless mesh networks (WMNs) several radios can operate within one node simultaneously on different channels. Due to frequency selective fading and varying output powers of WLAN cards the received signal strength on channels in the U-NII band can differ by several dB. Furthermore, power leakage from neighboring channels in the frequency spectrum can cause adjacent channel interference (ACI). Using a IEEE 802.11a testbed, we experimentally evaluate the achievable throughput of a multi-radio mesh network in a string topology under the impact of ACI and channel heterogeneity. Our results show that for low PHY rates the channel separation is a good indicator for throughput. However, for high PHY rates the propagation properties of a specific channel also need to be considered. Based on the results we provide recommendations for designing channel assignment algorithms for IEEE 802.11-based WMNs

  • 12.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    D’Andreagiovanni, Fabio
    Konrad-Zuse-Zentrum für Informationstechnik Berlin (ZIB), Germany.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Fair Optimization of Mesh-Connected WLAN Hotspots2015In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 15, no 5, p. 924-946Article in journal (Refereed)
    Abstract [en]

    In Wireless mesh networks mesh access points (MAPs) forward traffic wirelessly towards users or Internet gateways. A user device usually connects to the MAP with the strongest signal, as such MAP should guarantee the best quality of service. However, this connection policy may lead to: (i) unfairness towards users that are distant from gateways; (ii) uneven distribution of users to MAPs; and (iii) inefficient use of network paths. We present a new model and solution approach to the problem of assigning users to MAPs and routing the data within the mesh network with the objective of providing max–min fair throughput. The problem is formulated as a mixed-integer linear programming problem (MILP). Because of the inherent complexity of the problem, real size instances cannot be solved to optimality within the time limits for online optimization. Therefore, we propose an original heuristic solution algorithm for the resulting MILP. Both numerical comparisons and network simulations demonstrate the effectiveness of the proposed heuristic. For random networks, the heuristic achieves 98% of the optimal solution. Network simulations show that in medium-sized networks, the number of users with at least 1Mbit/s minimum end-to-end rate increases by 550% when compared with the classical signal-strength based association.

  • 13.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Adaptive Aggregierung von VoIP Paketen in Wireless Mesh Networks2008Conference paper (Refereed)
  • 14.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Architecture and Algorithms for User Association and Routing in Wireless Mesh Networks2011Conference paper (Other (popular science, discussion, etc.))
  • 15.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    KAUMesh Demo: A MultiRadio MultiChannel Mesh Testbed2009Other (Other (popular science, discussion, etc.))
    Abstract [en]

    In this demo, we will present KAUMesh, an experimental Wireless Broadband Mesh Network based on 802.11a/b/g WLAN devices that has been deployed at the Karlstad University Campus. KAUMesh comprises currently 20 mesh nodes, which are permanently installed to cover large areas inside the new House 21. Standard 802.11b/g based clients can be used to connect to the mesh as they would to any given normal WLAN access point. KAUMesh features multiple gateways that connect the mesh network towards the internet. By deploying multiple radio cards in mesh nodes, KAUMesh is able to fully exploit available spectrum in the mesh backbone. One radio card interface is used for transparent client access, using typically 802.11b/g mode. The mesh backhaul connectivity is established using multiple radio interfaces per mesh node. The interfaces involved in the backhaul use a hybrid channel assignment mechanism, which rebalances channel usage according to user demand. As the hybrid channel assignment involves channel switching, a novel scheduling approach for making the channel switching QoS aware has been developed. KAUMesh also supports 802.11e standard on the mesh interface to provide service differentiation on the mesh backhaul

  • 16.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    On Packet Aggregation for VoIP in Wireless Meshed Networks2007Conference paper (Refereed)
  • 17.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Method and System for Centralized Control of User Associations in Wireless Mesh Networks2012Patent (Other (popular science, discussion, etc.))
  • 18.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Peylo, Christoph
    Telekom Innovation Laboratories.
    Optimization of WLAN associations considering handover costs2012In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 255Article in journal (Refereed)
    Abstract [en]

    In Wireless Local Area Network (WLAN) hotspots the coverage areas of Access Points (APs) often overlap considerably. Current state of the art optimization models find the optimal AP for each user station by balancing the load across the network. Recent studies have shown that in typical commercial WLAN hotspots the median connection duration is short. In such dynamic network settings the mentioned optimization models might cause many handovers between APs to accommodate for user arrivals or mobility. We introduce a new mixed integer linear optimization problem that allows to optimize handovers but takes into account the costs of handovers such as signaling and communication interruption. Using our model and extensive numeric simulations we show that disregarding the handover costs leads to low performance. Based on this insight we design a new optimization scheme that uses estimates of future station arrivals and mobility patterns. We show that our scheme outperforms current optimization mechanisms and is robust against estimation errors

  • 19.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Peylo, Christoph
    Telekom Innovation Laboratories.
    Chow, Lawrence
    Stanford University.
    Collins, Bradley
    Stanford University.
    Bambos, Nicholas
    Stanford University.
    Daniel, Mellado
    Miguel, Sanchez
    A Software Defined Networking Approach for Handover Management with Real-Time Video in WLANs2012Conference paper (Refereed)
  • 20.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Sivchenko, Dmitry
    Method and system for deriving an aggregation delay for packet aggregation in a wireless network2011Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    System and method for deriving an aggregation delay for a packet aggregation in a wireless network comprising a controller for deriving an optimal aggregation delay at a network node depending on information relating to the channel quality related parameters at the network node in the wireless network.

  • 21.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Bayer, Nico
    Einsiedler, Hans-Joachim
    Sivchenko, Dmitry
    FUZPAG: A Fuzzy-Controlled Packet Aggregation Scheme for Wireless Mesh Networks2010In: Proceedings of the International Conference on Fuzzy Systems and Knowledge Discovery (FSKD'10), IEEE , 2010, p. 778-782Conference paper (Refereed)
    Abstract [en]

    Wireless mesh networks (WMNs) are wireless multi-hop backhaul networks in which mesh routers relay traffic on behalf of clients or other routers. Due to large MAC layer overhead, applications such as Voice over IP, which send many small packets, show poor performance in WMNs. Packet aggregation increases the capacity of IEEE 802.11-based WMNs by aggregating small packets into larger ones and thereby reducing overhead. In order to have enough packets to aggregate, packets need to be delayed and buffered. Current aggregation mechanisms use fixed buffer delays or do not take into account the delay characteristics of the saturated IEEE 802.11 MAC layer. In this work, we present FUZPAG, a novel packet aggregation architecture for IEEE 802.11-based wireless mesh networks. It uses fuzzy control to determine the optimum aggregation buffer delay under the current channel utilization. By cooperation among neighboring nodes FUZPAG distributes the buffer delay in a fair way. We implemented and evaluated the system in a wireless mesh testbed. For different network topologies we show that FUZPAG outperforms standard aggregation in terms of end-to-end latency under a wide range of traffic patterns.

  • 22.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Bayer, Nico
    Sivchenko, Dmitry
    An Experimental Comparison of Burst Packet Transmission Schemes in IEEE 802.11-based Wireless Mesh Networks2010In: Proceedings of IEEE Global Telecommunications Conference (GLOBECOM) 2010, IEEE , 2010, p. 1-5Conference paper (Refereed)
    Abstract [en]

    Wireless mesh networks (WMNs) are wireless multihop networks comprised of mesh routers, which relay traffic on behalf of clients and other nodes. Using the standard IEEE 802.11 distributed coordination function (DCF) as MAC layer, a node needs to contend for the medium each time it wants to transmit a packet. This creates high overhead in particular for small packets and leads to poor performance for real-time applications such as Voice over IP (VoIP) or online gaming. Burst packet transmission can increase the efficiency. For example, with the Transmission Opportunity limit (TXOPlimit) in IEEE 802.11e, a station may transfer several packets without contending for the channel in between. Similarly, IP packet aggregation combines several IP packets together and sends them as one MAC Service Data Unit. Originally, both schemes have been developed for singlehop networks only. Thus the impact on WMNs is unclear if the packets need to contend over multiple hops. In this paper, we use measurements from a 9-node WMN testbed to compare TXOPs and IP packet aggregation for VoIP in terms of fairness, network capacity and quality of user experience. We show that for low networks loads, both TXOPs and IP packet aggregation increase the VoIP quality compared to IEEE 802.11 DCF. However, in highly loaded networks IP packet aggregation outperforms the other schemes.

  • 23.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Cavalcanti de Castro, Marcel
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Paolo Delia, Francesco
    Avallone, Stefano
    OLSR and Net-X as a Framework for Channel Assignment Experiments: Poster Presentation2009In: Proceedings of the 4th ACM international workshop on Experimental evaluation and characterization WiNTECH 09, NewYork: ACM , 2009Conference paper (Refereed)
    Abstract [en]

    We present a software framework for channel assingment and routing experiments in multi-channel/multi-radio wireless mesh networks.Based on a plug-in architecture we develop a traffic demand-aware channel assignment algorithm. The evaluation in KAUMesh - an experimental multi-radio mesh network - shows around 30% throughput improvement with respect to a traffic un-aware channel assignment scheme

  • 24.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Chow, Lawrence
    Stanford Univ, Stanford, CA 94305 USA..
    Bambos, Nicholas
    Stanford Univ, Stanford, CA 94305 USA..
    Bayer, Nico
    Telekom Innovat Labs, D-10587 Berlin, Germany..
    Einsiedler, Hans
    Telekom Innovat Labs, D-10587 Berlin, Germany..
    Peylo, Christoph
    Telekom Innovat Labs, D-10587 Berlin, Germany..
    BEST-AP: Non-intrusive estimation of available bandwidth and its application for dynamic access point selection2014In: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 39, p. 78-91Article in journal (Refereed)
    Abstract [en]

    The coverage area of Access Points CAPS) in Wireless Local Area Networks (WLANs) often overlaps considerably. Hence, a station can potentially associate with many APs. In traditional IEEE 802.11 systems, the station associates to the AP with the strongest signal. This strategy may result in load imbalance between APs and thus low overall network throughput. This paper proposes a new mechanism for selecting the "best" AP based on a novel available bandwidth estimation scheme. The available bandwidth provided by an AP depends mainly on the signal quality and the load on the wireless channel. Based on measurements we first analyze how those factors vary stochastically over time and motivate why a frequent estimation of available bandwidth is necessary. We then develop BEST-AP, a system for Bandwidth ESTimation of Access Points, which uses regular data traffic to estimate the available bandwidth from all APs in reach in a non-intrusive way, even if they are on a different channel. Based on OpenFlow, BEST-AP allows the station to be associated with multiple APs simultaneously and to switch between APs with low overhead. Using the available bandwidth estimates, the system exploits the "best" AP for longer duration while probing the less good APs for shorter durations to update the bandwidth estimations. The evaluation in a WLAN testbed shows that with background load created from real WLAN traces, the dynamic selection of APs improves the throughput of a station by around 81%, compared to a static selection. When the station is mobile, the throughput increases by 176% on average.

  • 25.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Chow, Lawrence
    USA.
    Bambos, Nicholas
    USA.
    Bayer, Nico
    Germany.
    Einsiedler, Hans
    Germany.
    Peylo, Christoph
    Germany.
    Mellado, Daniel
    Spain.
    Sanchez, Miguel
    Spain.
    A software-defined networking approach for handover management with real-time video in WLANs2013In: Journal of Modern Transportation, ISSN 2095-087X, E-ISSN 2196-0577, Vol. 21, no 1, p. 58-65Article in journal (Refereed)
  • 26.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Peylo, Christoph
    Telekom Innovation Laboratories.
    Software Defined Networking for the Management and Operation of WLANs2013Other (Other (popular science, discussion, etc.))
  • 27.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Sivchenko, Dmitry
    Theoretical and Experimental Analysis of the Channel Busy Fraction in IEEE 802.112010In: Proceedings of Future Network & Mobile Summit 2010, IEEE , 2010, p. 1-9Conference paper (Refereed)
    Abstract [en]

    Optimizing the operation of IEEE 802.11 networks requires to estimate the load of the wireless channel. The channel busy fraction, which is the fraction of time in which the wireless channel is sensed busy due to successful or unsuccessful transmissions, can be used as such indicator. It can be obtained from e.g. the IEEE 802.11k channel load report or hardware-specific interfaces. Previously, the channel busy fraction has been used as a metric for different purposes such as routing and admission control. However, a thorough evaluation of the relationship between the busy fraction and other important characteristics such as the collision probability and throughput is missing. In this paper, we present an analytical model to study the channel busy fraction in non-saturated IEEE 802.11 networks. We validate the model with measurements in a testbed. The predictions from the model match measurements well. Furthermore, we demonstrate how to apply the model to estimate the available link bandwidth. Using measurements obtained from a testbed operated at 6 Mbit/s, we show that the channel busy fraction allows an accurate prediction of the available bandwidth with an error smaller than 70 Kbit/s.

  • 28.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Staehle, Barbara
    Staehle, Dirk
    Pries, Rastin
    Hirth,, Matthias
    Measuring One-Way Delay in Wireless Mesh Networks: An Experimental Investigation2009In: Proceedings of the 4th ACM workshop on Performance monitoring and measurement of heterogeneous wireless and wired networks, New York: ACM , 2009Conference paper (Refereed)
    Abstract [en]

    Wireless Mesh networks are multi-hop networks mostly based on IEEE 802.11 technology and are considered as a viable alternative for providing broadband wireless Internet access. As a consequence, they require support for Quality of Service or advanced mechanisms for selecting Internet gateways. One important requiredinformation is the one-way delay between different nodes. In this paper, we have developed, implemented, and evaluated an one-way delay estimation technique for wireless mesh networks which is based on estimating intra node queuing and inter node forwarding delay. An IP-header option field is used to accumulate the per hop delay estimate to provide an end-to-end estimate. We also outline problems with the implementation and compare results with real one-way delays obtained from a 14 node mesh testbed.We show how estimation accuracy depends on network load and provide insights into further improvements

  • 29.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Vestin, Jonathan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    CloudMAC - Using OpenFlow to Process 802.11 MAC Frames in the Cloud2013In: PIK - Praxis der Informationsverarbeitung und Kommunikation, ISSN 0930-5157, Vol. 36, no 1, p. 53-Article in journal (Refereed)
  • 30.
    Dely, Peter
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Vestin, Jonathan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Peylo, Christoph
    Telekom Innovation Laboratories.
    CloudMAC: An OpenFlow based Architecture for 802.11 MAC Layer Processing in the Cloud2012In: 2012 IEEE Globecom Workshops (GC Wkshps 2012): Proceedings of a meeting held 3-7 December 2012, Anaheim, California, USA, IEEE conference proceedings, 2012, p. 186-191Conference paper (Refereed)
  • 31.
    Kassler, Andreas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Cavalcanti de Castro, Marcel
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    VoIP Packet Aggregation based on Link Quality Metric for Multihop Wireless Mesh Networks2007Conference paper (Refereed)
    Abstract [en]

    Providing Voice over IP in WLAN based wireless meshed networks is an important service for the future wireless internet. However, the transmission of small (voice) packets imposes high overhead which leads to low capacity for VoIP over 802.11 based multihop meshed networks. By combining several small packets into larger aggregated ones, it is expected that overhead can be significantly reduced thus incapacity for VoIP services. When mesh relay nodes aggregate small packets, there is an inherent trade-off regarding packet size. Aggregating more packets leads to larger packets, reduces the overall number of packets in the mesh and thus reduces multi-hop contention and packet loss due to collisions. However, such larger aggregated packets can lead to higher packet loss for a link that operates at low signal quality. For such links, aggregating fewer packets can be beneficial. Classical aggregation strategies typically operate end-to-end without considering those aspects and are therefore suboptimal. In this paper, we propose a new adaptive hop-by-hop aggregation scheme that calculates target aggregation sizes per each hop based on wireless link characteristics. Simulation results show that our approach is very effective, outperforms static aggregation schemes in various performance parameters and increases capacity for VoIP in meshed networks significantly

  • 32.
    Kassler, Andreas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Beyer, Nico
    OpenFlow for Wireless Mesh Networks2011In: Proceedings of 20th International Conference on Computer Communications and Networks (ICCCN), Maui, HI: IEEE conference proceedings, 2011, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Several protocols for routing and forwarding in Wireless Mesh Networks (WMN) have been proposed, such as AODV, OLSR or B.A.T.M.A.N. However, providing support for e.g. flow-based routing where flows of one source take different paths through the network is hard to implement in a unified way using traditional routing protocols. OpenFlow is an emerging technology which makes network elements such as routers or switches programmable via a standardized interface. By using virtualization and flow-based routing, OpenFlow enables a rapid deployment of novel packet forwarding and routing algorithms, focusing on fixed networks. We propose an architecture that integrates OpenFlow with WMNs and provides such flow-based routing and forwarding capabilities. To demonstrate the feasibility of our OpenFlow based approach, we have implemented a simple solution to solve the problem of client mobility in a WMN which handles the fast migration of client addresses (e.g. IP addresses) between Mesh Access Points and the interaction with re-routing without the need for tunneling. Measurements from a real mesh testbed (KAUMesh) demonstrate the feasibility of our approach based on the evaluation of forwarding performance, control traffic and rule activation time.

  • 33.
    Kassler, Andreas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Skorin-Kapov, Lea
    Dobrijevic, Ognjen
    Matijasevic, Maja
    Towards QoE-driven Multimedia Service Negotiation and Path Optimization with Software Defined Networking2012In: Software, Telecommunications and Computer Networks (SoftCOM), 2012 20th International Conference on, IEEE Press, 2012Conference paper (Refereed)
    Abstract [en]

    This paper presents motivation and ongoing work towards a system for Quality of Experience (QoE)-driven path assignment for multimedia services. The system goal is to enable negotiation of service and network communication parameters between end-users and to assign the network paths that are used for delivering multimedia flows according to the agreed service configuration. The key concept behind the system is a centralized multi-user optimization of the path assignments, which maximizes QoE by taking into account service utility functions, network topology, link capacities, and delay. Based on the output of the optimization process, the system implementation uses the OpenFlow to set up forwarding paths for the network elements

  • 34.
    Vestin, Jonathan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Peylo, Christoph
    Telekom Innovation Laboratories.
    CloudMAC: Towards Software Defined WLANs2012In: Mobicom '12 Proceedings of the 18th annual international conference on Mobile computing and networking, Association for Computing Machinery (ACM), 2012, p. 393-396Conference paper (Refereed)
  • 35.
    Zhou, Shuqiao
    et al.
    Tsinghua University.
    Yuan, Ruixi
    Tsinghua University.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Mitigating Control Channel Saturation in the Dynamic Channel Assignment Protocol2011In: JCIT: Journal of Convergence Information Technology, ISSN 2233-9299, Vol. 6, no 6, p. 271-281Article in journal (Refereed)
    Abstract [en]

     Multi-channel MAC protocols that rely on a dedicated control channel (CC) for data channel reservation face the problem of control channel saturation. When the control channel becomes the bottleneck, data channels are not fully utilized and the spectrum allocated for the network is not used efficiently. For a popular dedicated control channel based multi-channel MAC protocol, the dynamic channel assignment protocol (DCA), we propose and compare two methods for mitigating control channel saturation. The first method is based on the ability of modern wireless cards to use different channel bandwidths. Increasing the bandwidth of the CC allows higher transmission rates and thereby relieves the saturation on the CC. The second method involves TXOP (Transmission Opportunity)-like burst-transmissions, where several date packets are transmitted using one reservation operation on the control channel. Network simulations and analysis show that, in an 802.11 based network, the bandwidth adaptation method yields a throughput improvement of around 30%. The TXOP mechanism performs much better and increases the throughput by a factor of 2 to 10, depending on the length of the data packets.

  • 36. Zola, Enria
    et al.
    Barcelo-Arroyo, Francisco
    Dely, Peter
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Expected Bit Rate for Terminals Moving According to the Random Waypoint Model in a WLAN Cell2013Conference paper (Refereed)
    Abstract [en]

    The IEEE 802.11 standard defines the different bit rates and modulation schemes to which a WLAN device may adapt according to the channel quality. User mobility may also have an impact on the available bit rate. This paper presents a study of the bit rate evolution along time for devices that move according to the Random Waypoint mobility pattern in WLAN cells. Simulation has been applied in order to obtain statistical results that permit to characterize the evolution of the bit rate behavior along time and to compute average results in the ideal case (without interference) and in the presence of interfering devices. Our results can be useful in the solution of optimization problems in which decision on where to connect must be taken based on some minimum guaranteed bit rate. They also can be useful in the design of inter and intra-cell handover methods and load balancing schemes.

  • 37. Zola, Enrica
    et al.
    Dely, Peter
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Barcelo-Arroyo, Francisco
    Robust Association for Multi-radio Devices under Coverage of Multiple Networks2013Conference paper (Refereed)
1 - 37 of 37
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