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  • 1.
    Bagula, Antoine
    et al.
    University of Cape Town.
    Inggs, Gordon
    University of Cape Town.
    Scott, Simon
    University of Cape Town.
    Zennaro, Marco
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    On the Relevance of Using Open Wireless Sensor Networks in Environment Monitoring2009In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 9, no 6, p. 4845-4868Article in journal (Refereed)
    Abstract [en]

    This paper revisits the problem of the readiness for field deployments of wireless sensor networks by assessing the relevance of using Open Hardware and Software motes for environment monitoring. We propose a new prototype wireless sensor network that fine-tunes SquidBee motes to improve the life-time and sensing performance of an environment monitoring system that measures temperature, humidity and luminosity. Building upon two outdoor sensing scenarios, we evaluate the performance of the newly proposed energy-aware prototype solution in terms of link quality when expressed by the Received Signal Strength, Packet Loss and the battery lifetime. The experimental results reveal the relevance of using the Open Hardware and Software motes when setting up outdoor wireless sensor networks.

  • 2. Bellagamba, Elisa
    et al.
    Kempf, James
    Sköldström, Pontus
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Link Failure Detection and Traffic Redirection in an Openflow Network2010Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    Failure detection and traffic redirection are implemented in an OpenFlow switch. Link failure detection packets, such as Bidirectional Forwarding Detection (BFD) packets, are periodically sent out on links to peer OpenFlow switches, such as via the Multi-protocol Label Switching (MPLS) Transport Profile (MPLS-TP). Link failure detection packets are received from the peer OpenFlow switches on the links, and monitored. A link failure is detected if no incoming link failure detection packets are received on a link for a predetermined interval. In the event of a link failure, traffic is redirected from the failed link to a backup link by altering entries on a flow table of the OpenFlow switch.

  • 3.
    Brewka, Lukasz
    et al.
    DTU.
    Sköldström, Pontus
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Gavler, Anders
    Acreo AB.
    Nordell, Viktor
    Acreo AB.
    Wessing, Henrik
    DTU.
    Dittmann, Lars
    DTU.
    ALPHA Proposal of mapping QoS parameters between UPnP home network and GMPLS access2011In: ACCESS NETWORKS, 2011, p. 226-239Conference paper (Refereed)
    Abstract [en]

     This paper is treating the interdomain QoS signaling between the home and access domains with a focus on applying it for providing QoS between a UPnP-QoS based home network and GMPLS based access network. The work presented here is defining a possible approach for an interface between UPnP-QoS and GMPLS in order to move towards end-to-end QoS establishment as well as investigating the complexity of such a solution. We present the QoS parameters and mechanisms in both UPnP-QoS and GMPLS and how they can be matched to create a coherent QoS architecture.

  • 4.
    Brewka, Lukasz
    et al.
    DTU.
    Sköldström, Pontus
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Gavler, Anders
    Acreo AB.
    Nordell, Viktor
    Acreo AB.
    Wessing, Henrik
    DTU.
    Dittmann, Lars
    DTU.
    QoS enabled resource allocation over an UPnP-QoS/€”GMPLS controlled edge2011In: 2011 IEEE Consumer Communications and Networking Conference, CCNC'2011, 2011, p. 218-222Conference paper (Refereed)
    Abstract [en]

    This paper focuses on the problem of coherent resource allocation within home and access networks. The interdomain QoS signaling discussed here enables the initiation of the QoS provisioning in the home and access from the end device in users home. The home network considered in this paper is UPnP-QoS enabled while the access network is GMPLS based. We propose and implement an interface between aforementioned network segments allowing for end-to-end QoS establishment. We present the QoS parameters and mechanisms in both UPnP-QoS and GMPLS and how they can be matched to create a coherent QoS architecture. Additionally we investigate the complexity of such a solution and present implementation results.

  • 5.
    Cho, Jeong-woo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Cho, Dong-ho
    KAIST (Korea Advanced Institute of Science and Technology).
    A Dynamic Buffer Management Scheme Based on Rate Estimation in Packet-Switched Networks2001In: IEEE Global Telecommunications Conference, 2001. GLOBECOM '01, IEEE Press, 2001, p. 2304-2310Conference paper (Refereed)
    Abstract [en]

    While traffic volume of real-time applications is rapidly increasing, current routers do not guarantee minimum QoS values of fairness and they drop packets in a random fashion. If routers provide a minimum QoS, resulting a less delay, reduced delay-jitter, more fairness, and smooth sending rates, TCP-friendly rate control (TFRC) can be adopted for real-time applications. We propose a dynamic buffer management scheme that meets the requirements described above, and can be applied to TCP flow and to data flow for transfer of real-time applications. The proposed scheme consists of a virtual threshold function, an accurate and stable per-flow rate estimation, and a per-flow exponential drop probability. We discuss how this scheme motivates real-time applications to adopt TCP-friendly rate control.

  • 6.
    Cho, Jeong-woo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Chong, Song
    KAIST (Korea Advanced Institute of Science and Technology).
    Stabilized Max-Min Flow Control Using PID and PII2 Controllers2005In: IEICE transactions on communications, ISSN 0916-8516, E-ISSN 1745-1345, Vol. E88-B, no 8, p. 3353-3364Article in journal (Refereed)
    Abstract [en]

     This paper describes an 'analytical framework for the weighted max-min flow control of elastic flows in packet networks using PID and PII2 controller when flows experience heterogeneous round-trip delays. Our algorithms are scalable in that routers do not need to store any per-flow information of each flow and they use simple first come first serve (FCFS) discipline, stable in that the stability is proven rigorously when there are flows with heterogeneous round-trip delays. We first suggest two closed-loop system models that approximate our flow control algorithms in continuous-time domain where the purpose of the first algorithm is to achieve the target queue length and that of the second is to achieve the target utilization. The slow convergence [1] of many rate-based flow control algorithms, which use queue lengths as input signals, can be resolved by the second algorithm. Based on these models, we find the conditions for controller gains that stabilize closed-loop systems when round-trip delays are equal and extend this result to the case of heterogeneous round-trip delays with the help of Zero exclusion theorem. We simulate our algorithms with optimal gain sets for various configurations including a multiple bottleneck network to verify the usefulness and extensibility of our algorithms.

  • 7.
    Cho, Jeong-woo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Chong, Song
    KAIST (Korea Advanced Institute of Science and Technology).
    Utility Max-Min Flow Control Using Slope-Restricted Utility Functions2005In: GLOBECOM '05: IEEE Global Telecommunications Conference, Vols 1-6: DISCOVERY PAST AND FUTURE, IEEE Press, 2005, p. 819-824Conference paper (Refereed)
    Abstract [en]

    We present a network architecture for the distributed utility max-min flow control of elastic and non-elastic flows where utility values of users (rather than data rates of users) are enforced to achieve max-min fairness. We provide a distributed link algorithm that does not use the information of users' utility functions. To show that the proposed algorithm can be stabilized not locally but globally, we found that the use of nonlinear control theory is inevitable. Even though we use a distributed How control algorithm, it is shown that any kind of utility function can be used as long as the minimum slopes of the functions are greater than a certain positive value. We believe that the proposed algorithm is the first to achieve utility max-min fairness with guaranteed stability in a distributed manner.

  • 8.
    Cho, Jeong-woo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Chong, Song
    KAIST (Korea Advanced Institute of Science and Technology).
    Utility Max-Min Flow Control Using Slope-Restricted Utility Functions2007In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 55, no 5, p. 963-972Article in journal (Refereed)
    Abstract [en]

    We present a network architecture for the distributed utility max-min flow control of elastic and nonelastic flows where utility values of users (rather than data rates of users) are enforced to achieve max-min fairness. The proposed link algorithm converges to utility max-min fair bandwidth allocation in the presence of round-trip delays without using the information of users' utility functions. To show that the proposed algorithm can be stabilized not locally but globally, we found that the use of nonlinear control theory is inevitable. Even though we use a distributed flow-control algorithm, it is shown that any kind of utility function can be used as long as the minimum slopes of the functions are greater than a certain positive value. Though our analysis is limited to the single-bottleneck and homogeneous-delay case, we believe that the proposed algorithm is the first to achieve utility max-min fairness with guaranteed stability in a distributed manner

  • 9.
    Cho, Jeong-woo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Jiang, Yuming
    NTNU (Norwegian University of Science and Technology).
    Basic Theorems on the Backoff Process in 802.112009In: Performance Evaluation Review, ISSN 0163-5999, E-ISSN 1557-9484, Vol. 37, no 2, p. 18-20Article in journal (Refereed)
  • 10.
    Cho, Jeong-woo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Kim, Seong-Lyun
    Yonsei University.
    Chong, Song
    KAIST (Korea Advanced Institute of Science and Technology).
    Capacity of Interference-Limited Ad Hoc Networks with Infrastructure Support2006In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 10, no 1, p. 16-18Article in journal (Refereed)
    Abstract [en]

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

  • 11.
    Cho, Jeong-woo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Le Boudec, Jean-Yves
    EPFL (École Polytechnique Fédérale de Lausanne).
    Jiang, Yuming
    NTNU (Norwegian University of Science and Technology).
    On the Validity of the Fixed Point Equation and Decoupling Assumption for Analyzing the 802.11 MAC Protocol2010In: Performance Evaluation Review, ISSN 0163-5999, E-ISSN 1557-9484, Vol. 38, no 2, p. 36-38Article in journal (Refereed)
    Abstract [en]

    Performance evaluation of the 802.11 MAC protocol is classically based on the decoupling assumption, which hypothesizes that the backoff processes at different nodes are independent. A necessary condition for the validity of this approach is the existence and uniqueness of a solution to a fixed point equation. However, it was also recently pointed out that this condition is not sufficient; in contrast, a necessary and sufficient condition is a global stability property of the associated ordinary differential equation. Such a property was established only for a specific case, namely for a homogeneous system (all nodes have the same parameters) and when the number of backoff stages is either 1 or infinite and with other restrictive conditions. In this paper, we give a simple condition that establishes the validity of the decoupling assumption for the homogeneous case. We also discuss the heterogeneous and the differentiated service cases and show that the uniqueness condition is not sufficient; we exhibit one case where the fixed point equation has a unique solution but the decoupling assumption is not valid

  • 12.
    Cho, Jeong-woo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Mo, Jeonghoon
    Yonsei University.
    Chong, Song
    KAIST (Korea Advanced Institute of Science and Technology).
    Joint Network-wide Opportunistic Scheduling and Power Control in Multi-cell Networks2007In: 2007 IEEE INTERNATIONAL SYMPOSIUM ON A WORLD OF WIRELESS, MOBILE AND MULTIMEDIA NETWORKS, VOL 1, IEEE Press, 2007, p. 1-12Conference paper (Refereed)
    Abstract [en]

    We present a unified analytical framework that maximizes generalized utilities of a wireless network by network-wide opportunistic scheduling and power control. That is, base stations in the network jointly decide mobile stations to be served at the same time as the transmission powers of base stations are coordinated to mitigate the mutually interfering effect. Although the maximization at the first glance appears to be a mixed, twofold and nonlinear optimization requiring excessive computational complexity, we show that the maximization can be transformed into a pure binary optimization with much lower complexity. To be exact, it is proven that binary power control of base stations is necessary and sufficient for maximizing the network-wide utilities under a physical layer regime where the channel capacity is linear in the signal-to-interference-noise ratio. To further reduce the complexity of the problem, a distributed heuristic algorithm is proposed that performs much better than existing opportunistic algorithms. Through extensive simulations, it becomes clear that network-wide opportunistic scheduling and power control is most suitable for fairness-oriented networks and underloaded networks.

  • 13. Dahlhammar, Tobias
    et al.
    Brown, Terrence
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Voices of entrepreneurship and small business immigrant enterprises in kista, stockholm2005In: Innovation and entrepreneurship in functional regions / [ed] Iréne Johansson, Trollhättan: University West , 2005Conference paper (Refereed)
  • 14.
    Dan, György
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Internet Video Transmission2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The Internet has rapidly evolved from being a scientific experiment to a commercial network connecting millions of hosts that carries traffic generated by a large amount of applications with diverse requirements. Its architecture was however designed to enable efficient point-to-point delivery of bulk data, and can not provide statistical guarantees on the timely delivery of delay sensitive data such as streaming and real-time multimedia. Thus, applications that require low loss probabilities in today's Internet have to use some end-to-end error recovery mechanism. For delay sensitive applications the introduced latency by the applied schemes has to be low as well. Traffic control functions such as delay limited shaping and forward error correction (FEC), and multiple description coding (MDC) have been proposed for variable bitrate video. Their major drawback is, however, that it is difficult to predict their efficiency, as it depends on many factors like the characteristics of the stream itself, the characteristics of the traffic in the network and the network parameters. Consequently, it is difficult to decide which control mechanisms to employ, how to combine them and to choose the right parameters (e.g. block length, code rate) for optimal performance.

    In this thesis we present results on the efficiency of traffic control functions and MDC for video transmission based on mathematical models and simulations. We investigate the efficiency of delay limited traffic shaping and the trade-offs in the joint use of traffic shaping and forward error correction. We identify the packet size distribution of the traffic in the network as an additional factor that may influence the efficiency of FEC, and present a thorough analysis of its possible effects. We present an analytical comparison of MDC versus media-dependent FEC and media-independent FEC, and based on the results we conclude that MDC is a promising error control solution for multimedia communications with very strict delay bounds in an environment with bursty losses. We combine the analytical results with traces from measurements performed on the Internet to evaluate how efficient these error control schemes are under real loss patterns. We compare the efficiency of MDC and media-dependent FEC in the presence of channel estimation errors; we propose a new rate allocation method, which is robust to mis-estimations of the channel state and which improves error resilience on non-stationary channels. Finally we present an analytical model of the performance of an end-point-based multimedia streaming architecture based on multiple distribution trees and forward error correction, and analyze the behavior of the architecture for a large number of nodes.

  • 15. Eklund, J.
    et al.
    Grinnemo, Karl-Johan
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Brunström, A.
    Theoretical analysis of an ideal startup scheme in multihomed SCTP2010In: Networked Services And Applications - Engineering, Control And Management, Springer, 2010, p. 155-166Conference paper (Refereed)
    Abstract [en]

    SCTP congestion control includes the slow-start mechanism to probe the network for available bandwidth. In case of a path switch in a multihomed association, this mechanism may cause a sudden drop in throughput and increased message delays. By estimating the available bandwidth on the alternate path it is possible to utilize a more efficient startup scheme. In this paper, we analytically compare and quantify the degrading impact of slow start in relation to an ideal startup scheme. We consider three different scenarios where a path switch could occur. Further, we identify relevant traffic for these scenarios. Our results point out that the most prominent performance gain is seen for applications generating high traffic loads, like video conferencing. For this traffic, we have seen reductions in transfer time of more than 75% by an ideal startup scheme. Moreover, the results show an increasing impact of an improved startup mechanism with increasing RTTs.

  • 16. Eklund, Johan
    et al.
    Grinnemo, Karl-Johan
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Baucke, Stephan
    Brunstrom, Anna
    Tuning SCTP failover for carrier grade telephony signaling2010In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 54, no 1, p. 133-149Article in journal (Refereed)
    Abstract [en]

    The Stream Control Transmission Protocol (SCTP) has not only been selected as the signaling transport protocol of choice in IETF SIGTRAN, the architecture that bridges circuit-switched and IP-based mobile core networks, but also plays a pivotal role in SAE/LTE, the next-generation UMTS/HSPA networks. To meet the redundancy requirements of telecom signaling traffic, SCTP includes a failover mechanism that enables rerouting of traffic from an unreachable network path to a backup path. However, the recommendations provided by IETF on how to configure the SCTP failover mechanism to meet telecom signaling requirements are kept quite general and leave much of the tuning to the telecom equipment vendor and/or operator. Several works by us and others have been carried out to study the effect of different SCTP parameters on the failover performance. The main contribution of this paper is that it gives a coherent treatment of how to configure the SCTP failover mechanism for carrier-grade telephony signaling, and provides practically usable configuration recommendations. The paper also discusses an alternate or complementary way of optimizing the SCTP failover mechanism by relaxing the exponential backoff that foregoes a retransmission timeout in SCTP. Some results showing significantly reduced failover times by use of this mechanism, with only marginal deteriorating effects on a signaling network, are discussed and analyzed in the paper. (C) 2009 Elsevier B.V. All rights reserved.

  • 17.
    Eliasson, Erik
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Minisip design overview2006Report (Other academic)
  • 18.
    Eliasson, Erik
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Secure VoIP performance on handheld devices2006Report (Other academic)
  • 19.
    Enström, Emma
    et al.
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Kreitz, Gunnar
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Niemelä, Fredrik
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Söderman, Pehr
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Kann, Viggo
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Five Years with Kattis – Using an Automated Assessment System in Teaching2011In: 2011 Frontiers in Education Conference (FIE), New York: IEEE , 2011Conference paper (Refereed)
    Abstract [en]

    Automated assessment systems have been employed in computer science (CS) courses at a number of different universities. Such systems are especially applicable in teaching algorithmic problem solving since they can automatically test if an algorithm has been correctly implemented, i.e., that it performs its specified function on a set of inputs. Being able to implement algorithms that work correctly is a crucial skill for CS students in their professional role, but it can be difficult to convey the importance of this in a classroom situation. Programming and problem solving education supported by automated grading has been used since 2002 at our department. We study, using action research methodology, different strategies for deploying automated assessment systems in CS courses. Towards this end, we have developed an automated assessment system and both introduced it into existing courses and constructed new courses structured around it. Our primary data sources for evaluation consists of course evaluations, statistics on students' submitted solutions, and experience teaching the courses. Authors of this paper have been participating in teaching all of the courses mentioned here.

  • 20. Fraile, F
    et al.
    Kopparhed, Dan
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Persson, Hans
    Guerri, J.C.
    Interactive TV Arena: a TestBed for Hybrid Broadcast/Broadband Services2009In: BMSB: 2009 IEEE INTERNATIONAL SYMPOSIUM ON BROADBAND MULTIMEDIA SYSTEMS AND BROADCASTING, 2009, p. 766-768Conference paper (Refereed)
    Abstract [en]

    This paper presents the architecture of a Hybrid Broadband Broadcast TestBed deployed in Gavle, Sweden, to conduct end user trials with Interactive TV Services. The platform offers an environment for the evaluation of Interactive TV services, technology and program formats for television.

  • 21.
    Fu, Jing
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Sjödin, Peter
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Intra-Domain Routing Convergence with Centralized Control2009In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 53, no 18, p. 2985-2996Article in journal (Refereed)
    Abstract [en]

    The decentralized control scheme for routing in current IP networks has been questioned, and a centralized routing scheme has been proposed as an alternative. In this paper, we compare the convergence of centralized control scheme with decentralized link-state routing protocols. We first review the architectural advantages and challenges of centralized control. Thereafter, we identify and discuss the components of the convergence time in both schemes. We present how to achieve fast routing convergence in networks with centralized control. in particular, we analyze how to distribute forwarding information efficiently. Finally, we perform simulation studies on the convergence time for both real and synthetic network topologies and study the impact of control element location, link weights, and number of failures on the convergence time. The results show that the centralized control scheme can provide faster routing convergence than link-state routing protocols.

  • 22.
    Fu, Jing
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Sjödin, Peter
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Loop-Free Updates of Forwarding Tables2008In: IEEE Transactions on Network and Service Management, ISSN 1932-4537, Vol. 5, no 1, p. 22-35Article in journal (Refereed)
    Abstract [en]

    When the forwarding paths in an IP network change due to a link failure or a link weight modification, the forwarding tables in the routers may need to be updated. Each of these updates may cause transient loops if they are not performed in an appropriate order. In this paper, we propose an order to update the forwarding tables that avoids transient loops for non-urgent changes. The order is obtained by studying the changes in the forwarding tables, therefore it can be used in networks running any routing protocols, and for any type of forwarding path changes. After presenting the order, we prove that it is correct, and present an efficient algorithm to compute the order. Thereafter, we present several algorithms for performing forwarding table updates in accordance with the order. We also discuss how the update algorithms can be applied to both networks with centralized control and decentralized routing protocols. Finally, we study the update algorithms’ performance on several network topologies and with varying parameter settings and for several types of forwarding path changes.

  • 23.
    Gidlund, Mikael
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Xu, Y Z
    An improved ARQ scheme with application to multi-level modulation techniques2004In: IEEE INTERNATIONAL SYMPOSIUM ON COMMUNICATIONS AND INFORMATION TECHNOLOGIES 2004 (ISCIT 2004), PROCEEDINGS, VOLS 1 AND 2: SMART INFO-MEDIA SYSTEMS, NEW YORK: IEEE , 2004, p. 973-978Conference paper (Refereed)
    Abstract [en]

    In this paper we present a simple but effective packet combined ARQ scheme for multi-level modulation schemes such as MPAM, MPSK and MQAM. We propose an ARQ scheme that rearrange the symbols between different transmissions and also use the modulation level M as an extra dimension to improve the quality of the signal and reduce the number of retransmissions per packet. The idea is to see the modulation level and number of retransmissions as an augmented signal space and use packet combining to improve the robustness and performance. Our results show that the proposed ARQ scheme obtain a 4 dB gain compared to a packet combined ARQ scheme employing Chase combining.

  • 24.
    Hidell, Markus
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Sjödin, Peter
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Hagsand, Olof
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    NACK-Oriented Reliable Multicast for Routing Table Distribution in Decentralized Routers2005In: 3rd Swedish National Computer Networking Workshop, SNCNW 2005, Halmstad, Sweden, 2005Conference paper (Refereed)
    Abstract [en]

    The requirements on IP routers are increasing for every new generation of designs. The driving forces behind this development are growing traffic volumes and demands for new services. We believe that a modular decentralized router design is well-suited to meet future requirements. However, a distributed design may, compared to a centralized system, introduce an additional cost for internal communication between the elements. In this paper we evaluate different transaction mechanisms for the internal communication. We study the suitability of reliable multicast for the internal distribution of large amounts of routing information. In particular, we evaluate NORM (NACK-Oriented Reliable Multicast) as a candidate protocol for our purposes.

  • 25.
    Hidell, Markus
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Sjödin, Peter
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Klockar, Tomas
    Carr-Motyckova, Lenka
    A Modularized Control Plane for BGP2007In: PDCS '07 Proceedings of the 19th IASTED International Conference on Parallel and Distributed Computing and System, Anaheim, CA, USA: ACTA Press, 2007Conference paper (Refereed)
    Abstract [en]

    The number of new services and protocols required in IP routers is steadily growing. This adds to the complexity of the router control plane and increases the amount of work that has to be performed by the control processor. Accordingly, the trend of augmenting the router functionality has an important impact on control plane performance and robustness. Traditionally, router control software is intertwined into a single complex system in a centralized fashion. In this paper, we put forward a new way to design the control plane, based on modularization of control software into independent modules that can be decentralized to multiple processing elements and executed concurrently. We have applied this design approach on BGP (Border Gateway Protocol), with the main purpose to do an experimental performance evaluation of distributed control plane processing. We find that the time to process and install a large number of BGP routes, for instance during start-up of BGP, can be significantly reduced if the workload is spread over multiple processing units. We also identify several approaches for improving robustness through the use of a modular decentralized control plane. Finally, we demonstrate that such a system can be realized using unmodified open source routing software.

  • 26.
    Jimenez, Raul
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Eriksson, Lars-Erik
    Dacc.
    Knutsson, Björn
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    P2P-NEXT: Technical and legal challenges2009Conference paper (Refereed)
    Abstract [en]

    P2P-Next aims at providing solutions and appli- cations for digital content production and distribution, while keeping a continued analytical focus on the regulatory arena and legal aspects.

    In this paper, we address netorking, access control, and payment in P2P content distribution, three topics which are not only technically challenging, but they also require careful consideration of related legal and commercial issues.

    Finally, a design proposal is presented. This design considers technical capabilities, legal requirements and it is flexible enough to support different business models.

  • 27.
    Jimenez, Raúl
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Kademlia on the Open Internet: How to Achieve Sub-Second Lookups in a Multimillion-Node DHT Overlay2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Distributed hash tables (DHTs) have gained much attention from the research community in the last years. Formal analysis and evaluations on simulators and small-scale deployments have shown good scalability and performance.

    In stark contrast, performance measurements in large-scale DHT overlays on the Internet have yielded disappointing results, with lookup latencies measured in seconds. Others have attempted to improve lookup performance with very limited success, their lowest median lookup latency at over one second and a long tail of high-latency lookups.

    In this thesis, the goal is to to enable large-scale DHT-based latency-sensitive applications on the Internet. In particular, we improve lookup latency in Mainline DHT, the largest DHT overlay on the open Internet, to identify and address practical issues on an existing system. Our approach is implementing and measuring backward-compatible modifications to facilitate their incremental adoption into Mainline DHT (and possibly other Kademlia-based overlays). Thus, enabling our research to have impact on a real-world system.

    Our results close the performance gap between small- and large-scale DHT overlays. With a median lookup latency below 200 ms and a 99\superscript{th} percentile of just above 500 ms, our median lookup latency is one order of magnitude lower than the best performing measurement reported in the literature. Moreover, our results do not show a long tail of high-latency lookups, unlike previous reports.

    We have achieved these results by studying how connectivity artifacts on the underlying network ---probably caused by firewalls and NAT devices on the Internet--- affect the DHT overlay. Our measurements of the connectivity of more than 3 million nodes reveal that connectivity artifacts are widespread and can severely degrade lookup performance.

    Scalability and locality-awareness have also been explored in this thesis, where different mechanisms have been proposed. Some of the mechanisms are planned to be integrated into Mainline DHT in future work.

  • 28.
    Jimenez, Raúl
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Knutsson, Björn
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    CTracker: a Distributed BitTorrent Tracker Based on Chimera2008In: Collaboration and the Knowledge Economy: Issues, Applications, Case Studies / [ed] Paul Cunningham and Miriam Cunningham, Amsterdam: IOS Press , 2008, p. 941-947Conference paper (Refereed)
    Abstract [en]

    There are three major open issues in the BitTorrent peer discovery system, which are not solved by any of the currently deployed solutions. These issues seriously threaten BitTorrent's scalability, especially when considering that mainstream content distributors could start using BitTorrent for distributing content to millions of users simultaneously in the near future.

    In this paper these issues are addressed by proposing a topology-aware distributed tracking system as a replacement for both centralized and Kademlia-based trackers.

    An experiment measuring most popular open BitTorrent trackers is also presented. It shows that centralized trackers are not topology aware. We conclude that an ideal topology-aware tracker would return peers whose latency to the requester peer is significantly lower than of a centralized tracker.

  • 29.
    Jimenez, Raúl
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Osmani, Flutra
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Knutsson, Björn
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Connectivity Properties of Mainline BitTorrent DHT Nodes2009In: 2009 IEEE NINTH INTERNATIONAL CONFERENCE ON PEER-TO-PEER COMPUTING (P2P 2009), NEW YORK: IEEE , 2009, p. 262-270Conference paper (Refereed)
    Abstract [en]

    The birth and evolution of Feer-to-Peer (P2P) protocols have, for the most part, been about peer discovery. Napster, one of the first P2P protocols, was basically FTP/HTTP plus a way of finding hosts willing to send you the file. Since then, both the transfer and peer discovery mechanisms have improved, but only recently have we seen a real push to completely decentralized peer discovery to increase scalability and resilience. Most such efforts are based on Distributed Hash Tables (DHTs), with Kademlia being a popular choice of DHT implementation. While sound in theory, and performing well in simulators and testbeds, the real-world performance often falls short of expectations. Our hypothesis is that the connectivity artifacts caused by guarded hosts (i.e., hosts behind firewalls and NATs) are the major cause for such poor performance. In this paper, the first steps towards testing this hypothesis are developed. First, we present a taxonomy of connectivity properties which will become the language used to accurately describe connectivity artifacts. Second, based on experiments "in the wild", we analyze the connectivity properties of over 3 million hosts. Finally, we match those properties to guarded host behavior and identify the potential effects on the DHT

  • 30.
    Jimenez, Raúl
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Osmani, Flutra
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Knutsson, Björn
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Sub-Second Lookups on a Large-Scale Kademlia-Based Overlay2011In: 11th IEEE International Conference on Peer-to-Peer Computing 2011 (P2P’11), IEEE , 2011, p. 82-91Conference paper (Refereed)
    Abstract [en]

    Previous studies of large-scale (multimillion node) Kademlia-based DHTs have shown poor performance, measured in seconds, in contrast to the far more optimistic results from theoretical analysis, simulations and testbeds. In this paper, we unexpectedly find that in the Mainline BitTorrent DHT (MDHT), probably the largest DHT overlay on the Internet, many lookups already yield results in less than a second, albeit not consistently. With the backwards-compatible modifications we present, we show that not only can we reduce median latencies to between 100 and 200 ms, but also consistently achieve sub-second lookups. These results suggest that it is possible to deploy latency-sensitive applications on top of large-scale DHT overlays on the Internet, contrary to what some might have concluded based on previous results reported in the literature.

  • 31.
    Jocha, Dávid
    et al.
    Ericsson Research.
    Kern, András
    Ericsson Research.
    Takács, Attila
    Ericsson Research.
    Sköldström, Pontus
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    MPLS-OpenFlow based Access/Aggregation network2011In: 10th GENI Engineering Conference (GEC10), Puerto Rico, 2011Conference paper (Refereed)
  • 32.
    Kern, András
    et al.
    Ericsson Research.
    Lajos Kis, Zoltán
    Ericsson Research.
    Jocha, Dávid
    Ericsson Research.
    Takács, Attila
    Ericsson Research.
    Sköldström, Pontus
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Nordell, Viktor
    Acreo AB.
    Split Architecture: OpenFlow based MPLS access/aggregation network2011Conference paper (Refereed)
  • 33.
    Kopparhed, Dan
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Experiences from a research and development project course in ICT2011In: INTED2011: 5TH INTERNATIONAL TECHNOLOGY, EDUCATION AND DEVELOPMENT CONFERENCE, 2011, p. 1755-1761Conference paper (Refereed)
    Abstract [en]

    In this paper I reflect on my experiences from involvement in numerous Research and Development (R&D) projects. While observing teams of students working on various challenges in projects, I discovered that a surprising number of students seemed more or less unaware of common methodologies, tools and practices used in modern software development - newer ones in general and about collaborative development and regarding open source software in particular. These observations have led to ideas for improvements in the course, such as teaching about and requiring the use of revision control systems and wikis. The science of project management is evolving, especially regarding software development. In my opinion, there is an untapped potential that may be released by putting increased effort in supporting students in learning about and applying modern project methodology, such as Agile methods. There are two roles in project management that stand in particular contrast to each other, the coach and the principal. While the principal is at times a quite nasty guy making "impossible" demands, the coach is the good guy the team can turn to for help in dealing with a difficult situation. There is also a third role that acts as a sort of mix between coach and principal, which could be called the domain expert. It is important that roles are well defined and understood by the teams. Senior students can assist the projects in various ways while gaining useful knowledge. However, it is important that they start training well before the projects, allowing coaches to study relevant project methodology well in advance of coaching the teams. Applying the suggestions in this paper gives many benefits, including improved project results, higher efficiency, fewer mistakes, and students learning valuable knowledge about useful modern tools and methodologies that will be immediately useful when graduating and starting to work in the project-driven industry.

  • 34.
    Larsen, Claus Popp
    et al.
    Acreo AB.
    Popov, Mikhail
    Acreo AB.
    Gavler, Anders
    Acreo AB.
    Wang, Kun
    Nordell, Viktor
    Acreo AB.
    Sköldström, Pontus
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Next generation active optical access networks (AON): latest results of the ALPHA project2011Conference paper (Refereed)
  • 35.
    Lee, Hyang-Won
    et al.
    KAIST (Korea Advanced Institute of Science and Technology).
    Cho, Jeong-woo
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Chong, Song
    KAIST (Korea Advanced Institute of Science and Technology).
    A Distributed Max-Min Flow Control Algorithm for Multi-rate Multicast Flows2004In: GLOBECOM '04: IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, VOLS 1-6, IEEE Press, 2004, p. 1140-1146Conference paper (Refereed)
    Abstract [en]

    We present a distributed algorithm to compute bandwidth max-min fair rates in a multi-rate multicast network. The significance of the algorithm, compared to previous algorithms [1], [21, [3], is that it is more scalable in that it does not require each link to maintain the saturation status of all sessions and virtual sessions travelling through it, more stable in that it converges asymptotically to the desired equilibrium satisfying the minimum plus max-min fairness even in presence of heterogeneous round-trip delays, and has explicit link buffer control in that the buffer occupancy of every bottlenecked link in the network asymptotically converges to the pre-defined value. In addition, we propose an efficient feedback consolidation algorithm which is computationally simpler than its hard-synchronization based counterpart and eliminates unnecessary consolidation delay by preventing it from awaiting backward control packets(BCPs) that do not directly contribute to the session rate. Through simulations we verity the performance of the proposed multi-rate multicast flow control scheme based on these two algorithms.

  • 36.
    Lee, Hyang-Won
    et al.
    KAIST (Korea Advanced Institute of Science and Technology).
    Cho, Jeong-woo
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Chong, Song
    KAIST (Korea Advanced Institute of Science and Technology).
    Distributed Max-Min Flow Control for Multi-rate Overlay Multicast2010In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 54, no 11, p. 1727-1738Article in journal (Refereed)
    Abstract [en]

    We present a distributed algorithm to compute bandwidth max-min fair rates in an overlay multicast network supporting multi-rate data delivery. The proposed algorithm is scalable in that it does not require each logical link to maintain the saturation status of all sessions and virtual sessions traveling through it, stable in that it converges asymptotically to the desired equilibrium satisfying the minimum plus max-min fairness even in the presence of heterogeneous round-trip delays, and has explicit link buffer control in that the buffer occupancy of every bottlenecked link in the network asymptotically converges to the pre-defined value. The algorithm is based on PI (proportional integral) control in the feedback control theory and by appealing to the Nyquist stability criterion, a usable stability condition is derived in the presence of sources with heterogeneous round-trip delays. In addition, we propose an efficient feedback consolidation algorithm which is computationally simpler than its hard-synchronization based counterpart and eliminates unnecessary consolidation delay by preventing it from awaiting backward control packets that do not directly contribute to the session rate. Through simulations we further verify the analytical results and the performance of the proposed multi-rate multicast flow control scheme based on these two algorithms.

  • 37. Marsh, Ian
    et al.
    Severiano, Juan Carlos Martın
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Nunes, Victor
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Maguire, Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    IEEE 802.11b voice quality assessment using crosslayer information.2006Conference paper (Refereed)
    Abstract [en]

    This paper reports on the suitability of IEEE802.11b networks for carrying real-time voice traffic, considering particularly the end terminals. More specifically we looked at such networks in different operating circumstances:an outdoor environment, an office environment,and the influence of competing traffic. Additionally wehave investigated the link protocol in combination with theapplication layer. Based on over 2500 recorded sessions,it can be generally concluded that the 802.11b protocolcan support real-time voice; particularly if the link transmissionrate is immediately lowered after an unsuccessful initial transmission. However, we did find situations where the voice quality deteriorated below commonly accepted values, such as when competing with high-rate TCP traffic,when intervening obstacles blocked the transmission path,and with certain uses of the RTS/CTS mechanism.

  • 38.
    Nordell, Viktor
    et al.
    Acreo AB.
    Gavler, Anders
    Acreo AB.
    Sköldström, Pontus
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    BFD-triggered, GMPLS-based, multi-layer ethernet access network protection2011In: 2011 Asia Communications and Photonics Conference and Exhibition, ACP 2011, 2011Conference paper (Refereed)
    Abstract [en]

    In this paper we present a solution for providing protection in a Ethernet based access and metro network. To accomplish this we targeted two issues, protection aimed path computation in networks which does not provide fully disjoint paths, and the design and implementation of bi-directional forward detection (BFD) protocol in a GMPLS controlled Ethernet network. To the best of our knowledge, neither issue has been previously addressed through a similar approach and is therefore to be considered novel in its design and implementation. Our implementation shows good performances and reliability in both performance testing and testbed experiments.

  • 39.
    Ntareme, Hervé
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Domancich, Sebastián
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Security and performance aspects of Bytewalla: A Delay Tolerant Network on smartphones2011In: Wireless and Mobile Computing, Networking and Communications (WiMob), 2011 IEEE 7th International Conference on, IEEE , 2011, p. 449-454Conference paper (Refereed)
    Abstract [en]

    This paper presents an implementation of a Delay Tolerant Network (DTN) on the Android platform on mobile smartphones that we named Bytewalla. Moreover, we present an implementation of a security solution for Bytewalla based on the IRTF DTN Bundle Security protocol specification to protect the bundle content while in transit to the destination. Then, we make a throughout analysis of the data transmission overhead of the security protected bundles, which has direct consequences on the power consumption and system performance. Our overall, conclusion is that the integration of DTN links in the general IP-network architecture is feasible and will make it easier to integrate DTN applications into communication-challenged areas. To our knowledge our implementation of the bundle protocol is the first for the Android platform.

  • 40.
    Ntareme, Hervé
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Zennaro, Marco
    ICTP – International Centre for Theoretical Physics, Trieste, Italy.
    Pehrson, Björn
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Delay Tolerant Network on smartphones: Applications for communication challenged areas2011In: ExtremeCom '11 Proceedings of the 3rd Extreme Conference on Communication: The Amazon Expedition, ACM Press, 2011Conference paper (Refereed)
    Abstract [en]

    This paper discusses the Delay Tolerant Network (DTN) serviceand protocol stack and presents an implementation of it on theAndroid platform that is called "Bytewalla". It allows the use ofAndroid phones for the physical transport of data betweennetwork nodes in areas where there are no other links available, orwhere existing links need to be avoided for security reasons or incase the Internet is shut down by a government authority like ithappened in some Arab countries during the spring of 2011.The implementation of a store and forward messaging applicationand a Sentinel Surveillance health-care application (SSA) thatruns on top of Bytewalla are presented together with a few usagescenarios. Our conclusion is that the integration of DTN links inthe general IP-network architecture on mobile phone platform isfeasible and will make it easier to integrate DTN applications intocommunication-challenged areas. To our knowledge ourimplementation of the bundle protocol is the first on the Androidplatform.

  • 41.
    Nungu, Amos
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Analysis of the Serengeti Broadband Network2011Report (Other academic)
    Abstract [en]

    Internet access is intermittent and very expensive in remoteareas in the developing world. The access is still mainly pro-vided via satellite links to other continents and, although thetransition to terrestrial networks has started, it will taketime to reach the under-served areas. To understand thelocal needs and traffic patterns in rural areas, we have an-alyzed Internet web traffic logs captured over a year froma municipal network deployed in remote areas in Tanzania.The web traffic logs analysis was complemented by user sur-veys on their actual usage.Our analysis reveals that popularity of social networkingand news websites increases over time.We have noticed manyother contents such as advertisements which we consider notrelevant to developing regions but consume the little band-width they have. Based on the insights gained from theanalysis, we have provided recommendations on how to op-timize the little bandwidth available. Further, we have de-ployed some of the recommendations in the current system.

  • 42.
    Nungu, Amos
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Brown, Terrence
    KTH, School of Industrial Engineering and Management (ITM).
    Pehrson, Björn
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Business Model for Developing World Municipal Broadband Network - A Case Study2011In: Global Information Infrastructure Symposium (GIIS), 2011, Da Nang, Vietnam: IEEE , 2011, p. 1-7Conference paper (Refereed)
    Abstract [en]

    A viable business model is key for the financial andoperational sustainability of community broadband network. Us-ing the public-private-partnership approach, stakeholder analysisand the business model canvas tool, we demonstrate a businessmodel that can guarantee financial and operational sustainabilityof community networks in rural developing regions. The businessmodel has been validated in a local broadband communicationnetwork built in rural Tanzania.

  • 43.
    Nungu, Amos
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Brown, Terrence
    KTH, School of Industrial Engineering and Management (ITM).
    Pehrson, Björn
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Challenges in Sustaining Municipal Broadband Networks in the Developing World2011In: E-TECHNOLOGIES AND NETWORKS FOR DEVELOPMENT, Verlag Berlin Heidelberg: Springer , 2011, Vol. 171, p. 26-40Conference paper (Refereed)
    Abstract [en]

    Municipal or community networks seem to be a constructivefirst step in the process of establishing sustainable broadband networksin areas where the demand for broadband communication services islarger than the supply. Besides meeting the acute demand, one purposeis to stimulate the market by demonstrating connectivity feasibility, toreduce the risks involved for commercial actors. One of the keys to thesustainability and scalability of such networks is a well designed andmanaged institutional framework based on the local prerequisites.In this paper, we report on our experience from the establishment ofthe Serengeti Broadband Network in Northern Tanzania. We have beenusing a public-private partnership approach to create a not-for-profitorganization to manage and operate a network first deployed as a researchand education effort. We present and discuss our approach, comparingand contrasting to other approaches found in the literature. We concludethat success requires local ownership. Thus, the institutional frameworkshould aim at creating local commitment and leadership.

  • 44.
    Nungu, Amos
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Knutsson, Björn
    Pehrson, Björn
    On Building Sustainable Broadband Networks in Rural Areas2011In: 2011 Technical Symposium at ITU Telecom World (ITU WT11), 2011, p. 135-140Conference paper (Refereed)
    Abstract [en]

    We present research on how to build sustainablebroadband networks in rural areas of developing regions. Due toan increasing political awareness of the importance of ICT fordevelopment, many such regions are now being networked. Thespecific design considerations are due to the technical and non-technical challenges found in those areas. Our research includesa pilot implementation in rural Tanzania.

  • 45.
    Nungu, Amos Muhunda
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Towards Sustainable Broadband Communication in Under-served Areas: A Case Study from Tanzania2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The problem discussed in this thesis is how to establish sustainable broadband markets in under-served areas. The purpose is to improve people’s living conditions by promoting efficient service delivery in education, health, and governance and alleviating poverty. Due to the high-perceived risks, the market forces have failed to bring ICT in these areas. The business community is reluctant to take on the supplier role.

    Earlier efforts through development partners have been focusing on connecting under-served areas to the global Internet via telecentres. However, most implementations could not operate beyond the initial funding for various reasons, especially the lack of understanding of the local needs where most technical solutions were imported from the developed world, not optimized to work under local conditions.

    We propose the creation of community or municipal owned “broadband islands”, defined as high speed communication broadband networks that do not depend on external connections for their operations. Using an Action Research participatory approach, we are emphasizing multi-stakeholder partnerships, and engaging the local community to contribute infrastructure, technical solutions and leadership. Our proposal is validated through the design and deployment of two pilot sites in rural areas of Tanzania. Our original contributions include 1) An overall model on how to establish and sustain broadband markets in under-served areas, making it scalable and reproducible. 2) technical innovations, especially the design and implementation of a low cost, low power-consuming, and robust router with integrated power management. 3) Organizational innovations by establishing institutional mechanisms at a local level in public-private-community partnership. 4) Innovative funding mechanisms by identifying partners who can pay on behalf of the end users and cut down costs through resource sharing schemes.

    The government of Tanzania has shown interest to use the pilot sites as models for extending the national backbone into other municipal. Also, discussions are underway to organize similar pilots in East Africa.

  • 46.
    Nungu, Amos
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Nsubis, Genesis
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Pehrson, Björn
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Serengeti Broadband2008In: The 2nd ACM SIGCOMM Workshop on Networked Systems for De-veloping Regions, New York, NY, USA: ACM , 2008Conference paper (Refereed)
    Abstract [en]

    This paper presents a broadband island defined by a fibre-opticcommunication network between Bunda and Serengeti, two ruraldistricts in the Mara region in northern Tanzania. The purpose ofthe network is to facilitate creation and sharing of information atgovernment institutions. The network is also expected to createjobs and entrepreneurial activities in these under-served areas.

    The network is comprised of an optical fibre backbone and wireless local area networks operating in license-free spectrum asaccess networks. The fibre is currently terminated at three locations. VLAN-capable Ethernet switches with long rangeoptical transceivers provide backbone transmission as well as fibre access. To minimize costs, routers and servers in the networkare all based on standard PC hardware and Free Open Sourcesoftware. The infrastructure is operated under an Open Accessregime, other ways of resource sharing like virtualization at thelink; network and application layers are explored.

    Although the broadband island defined by the fibre has anarrowband VSAT connection to the Internet, the focus on theservices provided in the network is local, focusing on e-government, education, healthcare and support to local entrepreneurs.

  • 47. Nungu, Amos
    et al.
    Olsson, Robert
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Pehrson, Björn
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Design and Implementation of an Inclusive Ubiquitous Access2012In: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 67, no 1, p. 79-94Article in journal (Refereed)
    Abstract [en]

    The development towards ubiquitous network access requires innovative solutions to get remote areas included, especially rural areas of developing regions. The challenges include robustness of network components, poor or non-existent power supply and sustainable business models. We argue that large scale user-driven community networks are becoming technically viable to deploy in areas that are short of supply of telecommunication services due to little or no commercial interest. To support this claim, we discuss the design of key network elements and careful power management based on alternative energy sources and storage. We also provide a status report from ongoing field-tests regarding provisioning of broadband network services in Serengeti, Tanzania, and outline briefly our strategy to achieve sustainability. On the technical side, we first discuss an affordable, high-performance, low-effect router based on open source software and standard off-the-shelf hardware offering both copper and fibre links. Our design is capable of forwarding more than 700 kpps at 22.3 W. The power consumption is considerably less than all alternatives in our comparison. Then we discuss power management and the use of batteries and super-capacitors as backup and storage solutions.

  • 48.
    Nungu, Amos
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Olsson, Robert
    Pehrson, Björn
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    On Powering Communication Networks in Developing Regions2011In: Computers and Communications (ISCC), 2011 IEEE Symposium on, Kerkyra, Greece: IEEE , 2011, p. 383-390Conference paper (Refereed)
    Abstract [en]

    The work behind this paper aims at demonstrat-ing innovative solutions for the establishment of sustainablecommunity broadband networks in areas where there is de-mand but no supply of broadband services. One of the majorchallenges turns out to be reliable power supply. To overcomethis challenge, we explore how to decrease the demand forpower as well as the feasibility of using alternative powersources, such as solar and wind, and alternative power storagetechnologies, such as batteries and ultra-capacitors.In this paper, we present data collected over 2 months fromthe Serengeti community network in rural Tanzania to discussthe quality of the existing power-grid and the feasibility ofusing solar and wind energy as alternative energy sources.The network backbone is based on 1Gbps Ethernet links overdark fibre while end-user connections are currently based onWiFi links.Our measurements regarding the quality of the power-gridshow up to 21 power-outages in one single day, with an averageof 2 outages per day. Some of the outages are due to plannedrationing schemes caused by insufficient power generationwhile some outages are due to poor wiring or installations.Our measurements and analysis of the feasibility of usingalternative power sources indicate wind speeds on the average2m/s and a persistent high-level insolation, making solar energythe prime candidate as an alternative source of electricity. Therelatively high cost of solar panels has to be mitigated byincreased energy efficiency of the network elements. We alsopropose power management to be included in the networkmanagement system to maximize the availability of the net-work services and decrease operational costs due to damagednetwork elements.

  • 49.
    Nungu, Amos
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Olsson, Robert
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Pehrson, Björn
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    On the design of inclusive ubiquitous access2011In: ICUFN 2011 - 3rd International Conference on Ubiquitous and Future Networks, Dalian, China: IEEE , 2011, p. 346-352Conference paper (Refereed)
    Abstract [en]

    The development towards ubiquitous network access requires innovative solutions to get remote areas included, especially rural areas of developing regions. The challenges include robustness of network components, poor or non-existent power supply and sustainable business models. We argue that large scale user-driven community networks are becoming technically viable to deploy in areas that are short of supply of telecommunication services due to little or no commercial interest. To support this claim, we discuss the design of key network elements and careful power management based on alternative energy sources and storage. We also provide a status report from ongoing field-tests regarding provisioning of broadband network services in Serengeti, Tanzania, and outline briefly our strategy to achieve sustainability. On the technical side, we first discuss an affordable, high-performance, low-effect router based on open source software and standard off-the-shelf hardware offering both copper and fibre links. Our design is capable of forwarding more than 700kpps at 22.3W. The power consumption is considerably less than all alternatives in our comparison. Then we discuss power management and the use of batteries and super-capacitors as backup and storage solutions.

  • 50.
    Nungu, Amos
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Olsson, Robert
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Pehrson, Björn
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Short paper - On the design of affordable and green high-performance routers for community networks2010In: Proceedings of the 4th ACM Workshop on Networked Systems for Developing Regions, NSDR '10, 2010, p. 11-Conference paper (Refereed)
    Abstract [en]

    We argue that large scale user-driven community networks are becoming viable in areas without access to telecommunication services due to lack of commercial interest. We discuss the design of a key component supporting this claim: a high-performance, low-power-consuming and affordable router with fibre optic capable of forwarding 2 Gbps, 220kpps, powered by only 25W, which is between 7% and 17% of the alternatives in our comparison. The cost of the one-off prototype was below a third of the prices of comparable proprietary solutions and half of other open source alternatives. It can be reduced further in series production. Future work will include widening of bottlenecks without increasing cost and field tests in rural African settings.

12 1 - 50 of 85
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