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  • 251.
    Chen, Jiajia
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Machuca, C.
    Jaeger, M.
    Cost vs. reliability performance study of fiber access network architectures2010Ingår i: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 48, nr 2, s. 56-65Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fiber to the home is the future-proof technology for broadband access networks. Several fiber access network architectures have been developed (e.g., point-to-point, active optical network, and passive optical network). PON is considered the most promising solution due to the relatively low deployment cost and high resource efficiency. Meanwhile, because of the growing demand for reliable service delivery, fault management is becoming more significant in all parts of communications networks. However, there is a trade-off between the cost of protection and the level of service reliability. Since economical aspects are most critical in the access part of networks, improving reliability performance by duplication of network resources (and capital expenditures) could be too expensive. Therefore, recent work has focused on PON protection schemes with reduced CAPEX. The future trend will probably migrate toward minimizing operational expenditures during the access network lifetime. The main contributions of this article include providing a general method for CAPEX and OPEX analysis that can be applied to any type of fiber access network with consideration of changed component cost in time and variable take rates, and comparing the total cost (i.e., sum of CAPEX and OPEX) for the selected representative architectures with and without protection for business and residential users in relation to reliability performance. The aim is to give a guideline for the design of the most cost-effective protection schemes, while maintaining acceptable service reliability.

  • 252.
    Chen, Lisan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Schiller Shi, Tingting
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Targeted News in an Intranet2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Microsoft har i SharePoint 2013 förbättrat användarnas personliga sidor (My Site) genom att sammankoppla dem i ett socialt nätverk. I förbättringen har ett personligt nyhetsflöde som visar händelser som användaren följer tillagts. Denna rapport avser att undersöka möjligheten att utöka det personliga nyhetsflödet med att lägga till en oberoende komponent i My Site. Komponenten ska tillåta användarna att prenumerera på företagsnyheter genom att välja bland olika nyhetskategorier.

    En prototyp av komponenten implementerades och resultatet uppfyllde de flesta kraven som ställdes i början av arbetet. Komponenten har lagts till i användarens My Site som en webb del och hämtar automatiskt de senaste företagsnyheterna som matchar användarens prenumeration. Den utvecklade prototypen kan förbättras både i funktion och design, men har uppfyllt behovet för denna rapport som avser att undersöka möjligheten att utöka det personliga nyhetsflödet i My Site med en sådan komponent.

    Eftersom projektmedlemmarna saknade förkunskaper i SharePoint och .NET utveckling innebar projektet nya utmaningar. Studenterna lärde sig att arbeta i SharePoint miljö samt i Microsoft Visual Studio för .NET utveckling.

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  • 253.
    Cheng, Yuxin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Passive Optical Top-of-Rack Interconnect for Data Center Networks2017Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Optical networks offering ultra-high capacity and low energy consumption per bit are considered as a good option to handle the rapidly growing traffic volume inside data center (DCs). However, most of the optical interconnect architectures proposed for DCs so far are mainly focused on the aggregation/core tiers of the data center networks (DCNs), while relying on the conventional top-of-rack (ToR) electronic packet switches (EPS) in the access tier. A large number of ToR switches in the current DCNs brings serious scalability limitations due to high cost and power consumption. Thus, it is important to investigate and evaluate new optical interconnects tailored for the access tier of the DCNs.

    We propose and evaluate a passive optical ToR interconnect (POTORI) architecture for the access tier. The data plane of the POTORI consists mainly of passive components to interconnect the servers within the rack as well as the interfaces toward the aggregation/core tiers. Using the passive components makes it possible to significantly reduce power consumption while achieving high reliability in a cost-efficient way.

    Meanwhile, our proposed POTORI’s control plane is based on a centralized rack controller, which is responsible for coordinating the communications among the servers in the rack. It can be reconfigured by software-defined networking (SDN) operation. A cycle-based medium access control (MAC) protocol and a dynamic bandwidth allocation (DBA) algorithm are designed for the POTORI to efficiently manage the exchange of control messages and the data transmission inside the rack.

    Simulation results show that under realistic DC traffic scenarios, the POTORI with the proposed DBA algorithm is able to achieve an average packet delay below 10 μs with the use of fast tunable optical transceivers. Moreover, we further quantify the impact of different network configuration parameters on the average packet delay. 

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  • 254.
    Cheng, Yuxin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Datavetenskap, Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Fiorani, Matteo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Lin, Rui
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    POTORI: A Passive Optical Top-of-Rack Interconnect Architecture for Data Centers2017Ingår i: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 9, nr 5, s. 401-411Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several optical interconnect architectures inside data centers (DCs) have been proposed to efficiently handle the rapidly growing traffic demand. However, not many works have tackled the interconnects at top-of-rack (ToR), which have a large impact on the performance of the data center networks (DCNs) and can introduce serious scalability limitations due to their high cost and power consumption. In this paper, we propose a passive optical ToR interconnect architecture (POTORI) to replace the conventional electronic packet switch (EPS) in the access tier of DCNs. In the data plane, POTORI relies on a passive optical coupler to interconnect the servers within the rack and interfaces toward the aggregation/core tiers. The POTORI control plane is based on a centralized rack controller responsible for managing the communications among the servers in the rack. We propose a cycle-based medium access control (MAC) protocol to efficiently manage the exchange of control messages and the data transmission inside the rack. We also introduce and evaluate a dynamic bandwidth allocation algorithm for POTORI, namely largest first (LF). Extensive simulation results show that, with the use of fast tunable optical transceivers, POTORI and the proposed LF strategy are able to achieve an average packet delay below 10 μs under realistic DC traffic scenarios, outperforming conventional EPSs. On the other hand, with slower tunable optical transceivers, a careful configuration of the network parameters (e.g., maximum cycle time of the MAC protocol) is necessary to obtain a good network performance in terms of the average packet delay.

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  • 255.
    Cheng, Yuxin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Fiorani, Matteo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Centralized Control Plane for Passive Optical Top-of-Rack Interconnects in Data Centers2016Ingår i: 2016 IEEE Global Communications Conference, GLOBECOM 2016 - Proceedings, IEEE conference proceedings, 2016, artikel-id 7841655Konferensbidrag (Refereegranskat)
    Abstract [en]

    To efficiently handle the fast growing traffic inside data centers, several optical interconnect architectures have been recently proposed. However, most of them are targeting the aggregation and core tiers of the data center network, while relying on conventional electronic top-of-rack (ToR) switches to connect the servers inside the rack. The electronic ToR switches pose serious limitations on the data center network in terms of high cost and power consumption. To address this problem, we recently proposed a passive optical top-of-rack interconnect architecture, where we focused on the data plane design utilizing simple passive optical components to interconnect the servers within the rack. However, an appropriate control plane tailored for this architecture is needed to be able to analyze the network performance, e.g., packet delay, drop rate, etc., and also obtain a holistic network design for our passive optical top-of-rack interconnect, which we refer to as POTORI. To fill in this gap, this paper proposes the POTORI control plane design which relies on a centralized rack controller to manage the communications inside the rack. To achieve high network performance in POTORI, we also propose a centralized medium access control (MAC) protocol and two dynamic bandwidth allocation (DBA) algorithms, namely Largest First (LF) and Largest First with Void Filling (LFVF). Simulation results show that POTORI achieves packet delays in the order of microseconds and negligible packet loss probability under realistic data center traffic scenarios.

  • 256.
    Cheng, Yuxin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Fiorani, Matteo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Reliability Analysis of Interconnects at Edge Tier in Datacenters2015Ingår i: 2015 17th International Conference on Transparent Optical Networks (ICTON), Institute of Electrical and Electronics Engineers (IEEE), 2015, artikel-id UNSP We.C3.1Konferensbidrag (Refereegranskat)
    Abstract [en]

    The growing popularity of cloud based applications is drastically increasing the traffic volume that datacenters have to handle. This brings the need for scalable, reliable, and energy-efficient interconnection networks inside the datacenters. Optical communication has been considered as a promising technology for datacenter applications due to its high energy- and cost-efficiency at ultra-high capacity. A typical datacenter interconnection network includes several tiers. Figure 1 shows an example with three tiers: edge, aggregation and core. Due to the large number of active devices on top of the rack (ToR) energy consumption at the edge tier is dominating the overall power consumed by all the switches within the datacenter [1-2]. Several passive optical interconnect approaches [2-4] have been proposed showing that replacing active optical devices by passive ones is possible to significantly reduce both the hardware cost and energy consumption, achieve lower maintenance complexity and offer a sufficient level of scalability. [GRAPHICS] Furthermore, several topologies, e.g., fat-tree [5], Quartz [6], are investigated in order to improve the resiliency and scalability, particularly for large-scale datacenters. However, it should be noted that the redundancy for these proposed topologies is often added in the aggregation and core tiers rather than the edge tier, due to the cost issue. Although passive optical ToR solution by nature could provide better reliability performance than its active counterpart, the intra-rack communication may still need survivability strategies to meet very high connection availability requirement. For instance, the required availability of fault-tolerant datacenter infrastructure (including electrical power supply, storage and distribution facilities) should be higher than 99.995% [7]. Then the expected availability for any connection established within the datacenter needs to be even higher, since the communication system is only a part of the site infrastructure. In this regard, we analyse reliability performance of optical interconnects and identify the key part to be protected. Based on it, we propose some reliable passive optical interconnects for the edge tier of the datacenter interconnection networks. They can achieve ultra-high connection availability for intra-rack communications and adapt to any topology, e.g., fat-tree and Quartz, designed to increase scalability and reliability performance for the overall datacenter network.

  • 257.
    Cheng, Yuxin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Fiorani, Matteo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Reliable and Cost Efficient Passive Optical Interconnects for Data Centers2015Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, nr 11, s. 1913-1916Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

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  • 258.
    Cheng, Zhuo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Hybrid Power Control in Time Division Scheduling Wideband Code Division Multiplex Access2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Med den höga datahastighet som Enhanced Uplink (EUL) medger kan en konventionell algoritm för effektkontroll baserad på signal to interference ratio (SIR) leda till effekthöjning beroende på självinterferens eller felaktigt SIR mål. Time division (TD) schedulering vid Wideband Code Division Multiple Access (WCDMA) anses vara en nyckelfunktion för att uppnå höga datahastigheter. I övergången mellan aktiv och inaktiv transmissionstidsintervall vid time division multiplexing (TDM) har effektoscillering/effektpeak observerats. Detta gör det nödvändigt att se över algoritmerna för effektkontroll vid olika scenarion av TD schedulering.

    Målet med effektkontrollen i denna studie är att minimera rise over thermal noise (RoT) för en given datahastighet givet begränsningen att kvaliteten på physical layer control channel är tillräcklig (beaktande att dedicated physical control channel (DPCCH) SIR inte understiger 3dB med en sannolikhet på som mest 5%). Ett annat mål är att minimera den lokala effektoscillationen (effektpeakar) som kan inträffa till exempel vid övergång mellan aktiv och inaktiv transmissionstidsintervall.

    De undersökta hybrida metoderna för effektkontroll är: (1) icke-parametrisk Generalized rake receiver SIR (GSIR) Inner Loop Power Control (ILPC) vid aktiv transmissionstidsintervall + Received Signal Code Power (RSCP) ILPC vid inaktiv transmissionstidsintervall och (2) RSCP ILPC under aktiv transmissionstidsintervall + GSIR ILPC under inaktiv transmissiontidsintervall. Båda metoderna jämförs med ren GSIR och ren RSCP ILPC.

    Länk nivå simulering med flera användare anslutna till en enda cell visar att:

    • Problemet med effektpeakar observeras tydligt vid GSIR + GSIR transmit power control (TPC) men generellt sett presterar den bra i alla studerade TD scenarion. GSIR presterar bättre än andra TPC metoder beträffande RoT, speciellt i TU kanal modellen. Detta beror på att metoden är bra på att motverka momentant förändrad fading och med god precision estimerar SIR. Bland alla presenterade TPC metoder är GSIR + GSIR TPC den bästa på att behålla en god kvalitet på DPCCH kanalen. Ingen effekthöjning har observerats vid GSIR + GSIR TPC.
    • RSCP + RSCP eliminerar problemet med effektpeakar och presterar bättre än andra TPC metoder presenterade under 3GPPs Pedestrial A (pedA) 3km/h kanal beträffande RoT. Dock är metoden generellt sett sämre på att behålla kontrollkanalens kvalitet än GSIR + GSIR TPC.
    • GSIR + GSIR ILPC eliminerar problemet med effektpeakar och presterar bättre än GSIR power control i ett scenario med 2 och 4 TDM high data rate (HDR) UE och 2 TDM HDR UE tillsammans med 4 Code Division Multiplex (CDM) LDR UE i pedA 3km/h kanalen beträffande RoT. Dock kan inte kvaliteten på kontrollkanalen behållas i detta fall heller under inaktiv transmissionstidsintervall.
    • Det är inte rekommenderat att använda RSCP + GSIR TPC eftersom den presterar sämst av alla TPC metoder beträffande RoT i de allra flesta fall. Till dess fördel är att den är den näst bästa på att behålla kvaliteten på kontrollkanalen. Effektpeakar har observerats när RSCP + GSIR TPC använts.

    För att behålla kontrollkanalens kvalitet används alltid en minimum SIR nivå ovanpå alla föreslagna TPC metoder. När det finns flera anslutna TDM HDR UEs i cellen indikerar resultaten att det är en utmaning att behålla kvalitetskraven på kontrollkanalen. På grund av detta kan det bli nödvändigt att begränsa antalet anslutna terminaler i en cell i ett TD scenario.

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  • 259.
    Chengegowda, Venkatesh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Analysis of Queues for Interactive Voice and Video Response Systems: Two Party Video Calls2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Videosamtal på mobila enheter är popularisera med tillkomsten av 3G. Den förbättrade nätkapacitet så tillgänglig möjliggör överföring av videodata över Internet. Det har prognos av flera VOIP serviceorganisationer att de nuvarande IVR-system kommer att utvecklas till röst och video Response (IVVR) System. Dock har denna utveckling många tekniska utmaningar på vägen. Arkitekturer för att genomföra kösystem för videodata och standarder för bland konvertering av videodata mellan format som stöds för uppringande är två av dessa utmaningar. Denna avhandling är en analys av köer och media kodkonvertering för IVVRs.

    En stor insats i detta arbete innebär att bygga en prototyp IVVR kösystem. Systemet är konstruerat med hjälp av en öppen källkod-server som heter Asterisk och MySQL-databas. Asterisk är en SIP-baserad Public Exchange Server (PBX) och även en utvecklingsmiljö för VOIP-baserade IVRs. Funktionella scenarier för SIP session etablering och motsvarande sessionen inställningar för den föreslagna kö modell mäts. Resultaten indikerar att prototypen tjänar som en tillräcklig modell för en kö, även om en betydande fördröjning införs för sessionsupprättandebegäran. Arbetet omfattar även analys av integrering DiaStar™ är en SIP-baserad media kodkonvertering motor till denna kö. Emellertid är detta system inte helt att fungera med DiaStar för media translation. The studie avslutas med ett omnämnande av de områden för framtida arbete med detta system och det allmänna tillståndet i IVVR kö-system i branschen.

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  • 260. Chiaraviglio, L.
    et al.
    Lorincz, J.
    Monti, Paolo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Towards sustainable and reliable networks with LIFETEL2015Ingår i: Proceedings - IEEE INFOCOM, IEEE conference proceedings, 2015, s. 39-40Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present the LIFETEL project, whose aim is trying to increase the device lifetime in telecommunication networks by exploiting energy-efficient techniques. In particular, we show that the lifetime of a device might increase when it is put in sleep mode. However, the device lifetime might decrease when power state variations (from sleep mode to full power) occur very frequently. Thus, there is a trade-off between the duration of sleep mode and its frequency. Moreover, we report a lifetime analysis for cellular and backbone devices, showing that the electricity saving may be exceeded by the costs due to the fact that devices fail more frequently compared to the situation in which they are always powered on. Thus, we claim that energy-aware network algorithms should be redesigned in order not to impact and to increase (when possible) the lifetime of network devices.

  • 261. Chiaraviglio, L.
    et al.
    Wiatr, Paweł
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Lorincz, J.
    Idzikowski, F.
    Listanti, M.
    Impact of energy-efficient techniques on a device lifetime2014Ingår i: 2014 IEEE Online Conference on Green Communications, OnlineGreenComm 2014, IEEE conference proceedings, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper focuses on the impact that energyefficient techniques have on the component lifetime in optical backbone networks. The study presented in the paper considers in particular the influence that green routing strategies have on the failure rate of Erbium Doped Fiber Amplifiers (EDFAs), i.e., if their lifetime is positively or negatively impacted when putting them into sleep mode in order to reduce their energy consumption. To this end, the paper proposes a model that estimates the failure rate acceleration factor as a function of: (i) for how long and how frequently a device is switched into sleep mode, and (ii) hardware parameters that characterize the device. The proposed model is then evaluated by considering an energyefficient Routing and Wavelength Assignment (RWA) strategy that targets saving energy by putting EDFAs into sleep mode. The results presented in the paper show that energy-efficient techniques may have the potential to lower the failure rate of EDFAs. However, this is true only under specific conditions, i.e., an energy-efficient strategy needs to be carefully planned in order to avoid frequent power state transitions, which result in shortening the lifetime of an EDFA.

  • 262. Chiaraviglio, Luca
    et al.
    Blefari-Melazzi, Nicola
    Liu, William
    Gutierrez, Jairo A.
    Van de Beek, Jaap
    Birke, Robert
    Chen, Lydia
    Idzikowski, Filip
    Kilper, Daniel
    Monti, Paolo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Wu, Jinsong
    5G in rural and low-income areas: Are we ready?2016Ingår i: PROCEEDINGS OF THE 2016 ITU KALEIDOSCOPE ACADEMIC CONFERENCE - ICTS FOR A SUSTAINABLE WORLD (ITU WT), IEEE, 2016, s. 99-106Konferensbidrag (Refereegranskat)
    Abstract [en]

    Current trends in telecommunication networks foresee the adoption of the,fifth generation (5G) of wireless networks in the near fixture. However; a large number of people are living without coverage and connectivity. To face this issue, we consider the possibility of deploying 5G networks in rural and low-income zones. After detailing the current state-of-the-art, we consider the main challenges that need to be faced. Moreover; we define the main pillars to follow in order to deploy 5G networks in such zones, as well as a proposal of a future network architecture.

  • 263. Chiaraviglio, Luca
    et al.
    Wiatr, Pawel
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Lorincz, Josip
    Idzikowski, Filip
    Listanti, Marco
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Is Green Networking Beneficial in Terms of Device Lifetime?2015Ingår i: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 53, nr 5, s. 232-240Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article analyzes the impact that sleep mode (SM)-based green strategies have on the reliability performance of optical and cellular network elements. First, we consider a device in isolation (i. e., not plugged into a network in operation), showing how operational temperature and temperature variations, both introduced by SM, impact its lifetime. We then evaluate, from an operational cost perspective, the impact of these lifetime variations, showing that some devices are critical, that is, their achievable energy savings might not cover the potential additional reparation costs resulting from being put in SM too frequently. Moreover, we present a model for evaluating the impact of SM on the lifetime of a device plugged into an operational network. The analysis considers two case studies (one based on the optical backbone and one on cellular networks) showing that the lifetime of a device is influenced by both the hardware parameters, which depend on the specific design of the device, and the SM parameters, which instead depend on the energy-efficient algorithm used, the network topology, and the traffic variations over time. Our results show that (i) the changes in the operational temperature and the frequency of their variation are two crucial aspects to consider while designing a SM-based green strategy, and (ii) the impact of a certain SM-based strategy on the lifetime of network devices is not homogeneous (i. e., it can vary through the network).

  • 264.
    Chincoli, Michele
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Valcarenghi, Luca
    Scuola Superiore Sant'Anna.
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Investigating the Energy Savings of Cyclic Sleep with Service Guarantees in Long Reach PONs2012Ingår i: Asia Communications and Photonics Conference, ACP, 2012, s. ATh1D.3-Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper evaluates what are the conditions, in terms of increased overhead time and number of optical network units (i.e., ONUs), in which cyclic sleep based techniques are effective in Long Reach PONs.

  • 265.
    Cho, Jeong-woo
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Jiang, Yuming
    NTNU (Norwegian University of Science and Technology).
    Fundamentals of the Backoff Process in 802.11: Dichotomy of the Aggregation2015Ingår i: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 61, nr 4, s. 1687-1701Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper discovers fundamental principles of the backoff process that governs the performance of IEEE 802.11. A simplistic principle founded upon regular variation theory is that the backoff time has a truncated Pareto-type tail distribution with an exponent of $ { (log gamma !)/log m}$ ( $boldsymbol {m}$ is the multiplicative factor and $ {gamma }$ is the collision probability). This reveals that the per-node backoff process is heavy-tailed in the strict sense for $ { gamma > 1/m^{2}}$ , and paves the way for the following unifying result. The state-of-the-art theory on the superposition of the heavy-tailed processes is applied to establish a dichotomy exhibited by the aggregate backoff process, putting emphasis on the importance of time-scales on which we view the backoff processes. While the aggregation on normal time-scales leads to a Poisson process, it is approximated by a new limiting process possessing long-range dependence (LRD) on coarse time-scales. This dichotomy turns out to be instrumental in formulating short-term fairness, extending existing formulas to arbitrary population, and to elucidate the absence of LRD in practical situations. A refined wavelet analysis is conducted to strengthen this argument.

  • 266.
    Cho, Jeong-woo
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Le Boudec, Jean-Yves
    EPFL (École Polytechnique Fédérale de Lausanne).
    Jiang, Yuming
    NTNU (Norwegian University of Science and Technology).
    On the Asymptotic Validity of the Decoupling Assumption for Analyzing 802.11 MAC Protocol2012Ingår i: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 58, nr 11, s. 6879-6893Artikel i tidskrift (Refereegranskat)
    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. This decoupling assumption results from mean field convergence and is generally true in transient regime in the asymptotic sense (when the number of wireless nodes tends to infinity), but, contrary to widespread belief, may not necessarily hold in stationary regime. The issue is often related with the existence and uniqueness of a solution to a fixed point equation; however, it was also recently shown that this condition is not sufficient; in contrast, a sufficient condition is a global stability property of the associated ordinary differential equation. In this paper, we give a simple condition that establishes the asymptotic validity of the decoupling assumption for the homogeneous case (all nodes have the same parameters). We also discuss the heterogeneous and the differentiated service cases and formulate a new ordinary differential equation. We show that the uniqueness of a solution to the associated fixed point equation is not sufficient; we exhibit one case where the fixed point equation has a unique solution but the decoupling assumption is not valid in the asymptotic sense in stationary regime.

  • 267.
    Cho, Jeong-woo
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Yi, Yung
    KAIST (Korea Advanced Institute of Science and Technology).
    On the Payoff Mechanisms in Peer-Assisted Services With Multiple Content Providers: Rationality and Fairness2014Ingår i: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 22, nr 3, s. 731-744Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper studies an incentive structure for cooperation and its stability in peer-assisted services when there exist multiple content providers, using a coalition game-theoretic approach. We first consider a generalized coalition structure consisting of multiple providers with many assisting peers, where peers assist providers to reduce the operational cost in content distribution. To distribute the profit from cost reduction to players (i.e, providers and peers), we then establish a generalized formula for individual payoffs when a "Shapley-like" payoff mechanism is adopted. We show that the grand coalition is unstable, even when the operational cost functions are concave, which is in sharp contrast to the recently studied case of a single provider where the grand coalition is stable. We also show that irrespective of stability of the grand coalition, there always exist coalition structures that are not convergent to the grand coalition under a dynamic among coalition structures. Our results give us an incontestable fact that a provider does not tend to cooperate with other providers in peer-assisted services and is separated from them. Three facets of the noncooperative (selfish) providers are illustrated: 1) underpaid peers; 2) service monopoly; and 3) oscillatory coalition structure. Lastly, we propose a stable payoff mechanism that improves fairness of profit sharing by regulating the selfishness of the players as well as grants the content providers a limited right of realistic bargaining. Our study opens many new questions such as realistic and efficient incentive structures and the tradeoffs between fairness and individual providers' competition in peer-assisted services.

  • 268.
    Choudrey, Sajaval
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Hiltunen, Kim
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Moln för Försvarsmakten2015Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    En organisation med ett så stort ansvar som Försvarsmakten behöver ständigt nya sätt att utvecklas och effektivisera sin drift, administration och organisation. Ett informationshanteringssystem i molnmiljö som grund skulle innebära en modernisering av administrationen inom organisationen och har potentialen att uppfylla Försvarsmaktens förbättringskrav. Arbetet har som huvudmål att ta fram och analysera lösningsförslag för hur Försvarsmakten skulle kunna använda sig av molnbaserade IT-system. I den första delen av arbetet ges en grundläggande introduktion till molnteknologin som även innefattar säkerhetsaspekter. Efter detta presenteras allmän information om Försvarsmakten, deras nuvarande IT-system samt de krav som ställs när det kommer till implementation av nya IT-system inom organisationen. Två olika molntjänster från WMware och Cloudstack undersöks för att se hur dessa skulle kunna användas för en eventuell implementation inom Försvarsmakten. Analysen av de två olika molntjänsterna fokuserar främst på säkerhetsaspekter, då det är ett viktigt fokusområde för Försvarsmakten.

    Ett annat område som arbetet har som syfte att undersöka är ekonomin för molntjänster. Detta för att se om en eventuell implementation är lönsam för Försvarsmakten eller inte.

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  • 269.
    Christos, Vouzas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Wireless Data Aquisition in Dairy Farms2005Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Wireless communications in dairy farms can be used in order to provide the farmer with useful information such as the activity of the cows. Nowadays, DeLaval is commercially using a wireless uplink system for cows’ activity monitoring limited though mostly to the indoors area of a farm. Throughout this paper we present four systems that can be used in dairy farms for extending the coverage area while also introduce a duplex two-way(uplink and downlink) communication scheme. We argue that the main trade off between the proposed systems is the current consumption versus the required coverage area. We evaluate the proposed systems and show the advantages of a duplex communication. Further on, we proceed in a simple cost analysis of the systems that is essential since they are addressing to a commercial reality.

  • 270.
    Chughtai, Mohsan Niaz
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik. KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Study of physical layer impairments in high speed optical networks2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The work done in this thesis focuses on the impact of transmission impairments in high speed optical networks. Specifically it focuses on the impact of nonlinear impairments in long haul fiber optic data transmission. Currently deployed fiber optic transmission networks are running on NRZ OOK modulation formats with spectral efficiency of only 1 bit/symbol. To achieve spectral efficiency beyond 1 bit/symbol, fiber optic communication systems running on advanced modulation formats such as QPSK are becoming important candidates. The practical deployment of QPSK based fiber optic communication system is severely limited by Kerr-induced nonlinear distortions such as XPM and XPolM, from the neighboring NRZ OOK channels. In this thesis we focus on the impact of nonlinear impairments (XPM and XPolM) in fiber optical transmission systems running on QPSK modulation with both differential and coherent detection. The dependence of impact of nonlinear impairments on SOP, baud rate of the neighboring NRZ OOK channels and PMD in the fiber, is analyzed in detail through numerical simulations in VPItransmission Maker®. In this thesis we also analyze digital signal processing algorithms to compensate linear and nonlinear impairments in coherent fiber optic communication systems. We propose a simplification of the existing method for joint compensation of linear and nonlinear impairments called "digital back propagation". Our method is called "weighted digital back propagation". It achieves the same performance of conventional digital back propagation with up to 80% reduction in computational complexity.In the last part of the thesis we analyze the transmission performance of a newly proposed hybrid WDM/TDM protection scheme through numerical simulation in VPItransmission Maker®. The transmission performance of the hybrid WDM/TDM PON is limited by impairments from passive optical devices and fiber optical channel.

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  • 271.
    Châtaignier, Arnaud
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Ahmed, Ashraf Awadelkarim Widaa
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Teslenko, Maxim
    Markendahl, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Regulation development on licensed shared access and TV white spaces2014Ingår i: Der Open-Access-Publikationsserver der ZBW, Brussels: ITS , 2014Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    For several years, the demand for data has increased. Furthermore, this is a growing trend. There are three ways to meet this demand. One option is to make the network denser; this implies large investments. We can work on improving the bandwidth efficiency; unfortunately, the channel limit is about to be reached[1]. Finally, the bandwidth allocated to telecommunication can be enlarged. Indeed, there are large spaces on spectrum which have been underused by the army or by the TV broadcasters. These players employ only a part of their allocated frequencies or use them only in a restricted area or time. Thus, regulatory frameworks are under construction to allow second users to exploit the locally unused frequencies without harming the incumbent. The two most advanced projects in this area are Licensed Share Access (LSA) and TV White Spaces (TVWS). Under LSA, an agreement is settled between an incumbent who underuses its spectrum (e.g: the Army) and one to several second users (share licensees). The agreement states, among other things, the area where the share licensees can deploy their networks and the conditions leading to its termination. In the case of TVWS, which takes advantage of the locally unused TV frequencies, the number of second users is unlimited and there is no direct contract with the incumbents (TV broadcasters and PMSE1 ). Instead, second users have to obtain the regulator authorization. Concretely, second users inform a database of their localization and the characteristics of their devices and will get in return available channels and power limitations. Even if there is a common understanding of these regulatory frameworks, regulators[2][3] are still working on the definition. This paper aims at presenting in several countries the trends in the regulation of TVWS and LSA. Aspects such as normalization, authorized uses, and allocated bandwidths will be highlighted. From this overall regulatory picture, this research will provide insight on the business development around TVWS and LSA.

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  • 272.
    Collin, Guillaume
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Chazalet, Boris
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Exploiting cooperative behaviors for VoIP communication nodes in a wireless local area network2007Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The purpose of this project was to implement a new design for VoIP communication in a wireless local area. One of the main goals was to experiment with a new approach that exploits cooperative behaviors. By cooperative we mean that the nodes try to cooperate so as to achieve higher cell capacity.

    VoIP communications has such specific data flows that it is interesting to build protocols that exploit these characteristics, for example for speech these characteristics are: regularity and timeconstrained delivery. Furthermore the wireless local area network brings another dimension in terms of all of the nodes sharing a wireless cell, as the nodes will share a common bandwidthlimited media. In the current standard for wireless local area networks the computers in the cell have to contend to get access to the shared media which can lead to delays, even if the bandwidth needed is much lower than the bandwidth available. If we focus on the needs of VoIP, one way to improve this is for all nodes to cooperate by organizing themselves to efficiently share the media. If they can agree with each other on what time each node will transmit, then they don't need to contend anymore. Thus the VoIP packets can reach their destination on time and while minimizing the use of resources in this cell.

    In this project we have designed and test a proof of concept of this cooperation in order to prove that it can work and to show what effects and performance it implies. This work can also be seen more generally as contextawareness research where the contextawareness is used to provide input to the cooperative behavior.

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  • 273. Colman-Meixner, C.
    et al.
    Figueiredo, G. B.
    Fiorani, Matteo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Tornatore, M.
    Mukherjee, B.
    Resilient cloud network mapping with virtualized BBU placement for cloud-RAN2017Ingår i: 2016 IEEE International Conference on Advanced Networks and Telecommunications Systems, ANTS 2016, Institute of Electrical and Electronics Engineers (IEEE), 2017, artikel-id 7947790Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cloud Radio Access Network (C-RAN) will improve mobile radio coordination and resource efficiency by allowing baseband processing unit (BBU) functions to be virtualized and centralized, i.e., deployed in a BBU hotel. We consider a BBU hoteling scheme based on the concept of access cloud network (ACN). An ACN consists of virtualized BBUs (vBBUs) placed in metro cloud data centers (metro DCs). A vBBU is connected to a set of remote radio heads (RRHs). ACN resiliency against network and processing failures is critical for C-RAN deployments. Hence, in this study, we propose three protection approaches: 1+1 ACN protection, 1+1 ACN and vBBU protection, and partial ACN protection. Simulation results show that both 1+1 ACN and 1+1 ACN and vBBU protection requires large capacity for backup to provide 100% survivability for singlelink and single-DC failures. As a result, we suggest a partial ACN protection approach which provides degraded services with only 8% additional network resources.

  • 274.
    Costa, J.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Zander, Jens
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Context-Aware Framework for Energy Efficient Machine-to-Machine CommunicationsIngår i: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cellular network based Machine-to-Machine(M2M) communications have been growing rapidly in recentyears, being used in a wide range of services such as security,metering, health, remote control, tracking and so on. A criticalissue that needs to be considered in M2M communications isthe energy efficiency, typically the machines are powered bybatteries of low capacity and it is important to optimize the waythe power is consumed. In search of better M2M systems, wepropose a context-aware framework for M2M communicationsso the machine type communication (MTC) devices dynamicallyadapt their settings depending on a series of characteristicssuch as data reporting mode and quality of service (QoS)features so higher energy efficient is achieved, extending theoperating lifetime of the M2M network. Simulations results willbe provided for four commonly used M2M applications: homesecurity, telehealth, climate and smart metering, showing thatconsiderable energy savings and operating lifetime extension onthe network can be achieved. Thus, contexts play an importantrole on the energy efficiency of a M2M system.

  • 275.
    Costa, Javier Mendonca
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Miao, Guowang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Context-Aware Machine-to-Machine Communications2014Ingår i: 2014 IEEE CONFERENCE ON COMPUTER COMMUNICATIONS WORKSHOPS (INFOCOM WKSHPS), IEEE , 2014, s. 730-735Konferensbidrag (Refereegranskat)
    Abstract [en]

    As a key enabler of Internet of things, cellular network based Machine-to-Machine (M2M) communications have been growing rapidly in recent years, being used in a wide range of services such as security, metering, health, remote control, tracking, and so on. A critical issue in M2M communications is the energy efficiency as typically the machine devices are powered by batteries of low capacity and thus, it is the key to optimize their consumption. To achieve higher energy efficiency, this paper proposes the adoption of contexts through a generic context-aware framework for M2M communications. With this framework, machine devices dynamically adapt their settings depending on a series of characteristics such as data reporting mode, QoS features, and network conditions to achieve higher energy efficiency and extend the operating lifetime of M2M networks. Simulation results are provided for four commonly used M2M applications. The results demonstrate considerable energy savings and operating lifetime extension on the network when the proposed context-aware framework is used. Thus, it is shown that contexts play an important role on the energy efficiency of M2M systems.

  • 276.
    Crespo Ramírez, Daniel
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Smartphone traffic patterns2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Den växande populariteten för nya generationens mobila terminaler, så kallade"smartphones", har ökat både antal och sådana produkter. Dessa enheter utnyttjar de resursersom Universal Mobile Telecommunication Services (UMTS) att få tillgång till on-line tjänster såsom web webbläsning, e-post, ljud och video streaming, osv. UMTS-nät har hantera med en ökande mängd data som genereras trafik bysmartphones. På grund av det faktum attsmartphone är batteridriven och försöker för att tillgodose behoven hos både applikationer och mänskliga användare det finns ett behov att vara smartare om hur man kan hantera både nätverk och terminaler resurser.

    Den avhandling undersöker möjligheten att göra en bättre användning av nätverk och terminaler resurser genom att utnyttja samband i händelserna smartphone-genererade trafik. Vi föreslår en mekanism genom vilken nätet kan förutsäga om terminalen kommer att ta fram dataöverföring orreception i en nära framtid, baserat på tidigare händelser i trafiken. Enligt denna förutsägelse, kommer nätet att kunna avgöra om den håller eller frigör resurser till terminalen. Vi analyserar nytta nätet och terminalen synvinkel. Vi beskriver också en metod för att uppskatta övre gränsen för tiden till nästa sändning eller mottagning av data inom ens nar framtidd.

    Vi visar att det är möjligt att minska den tid som varje terminal avfall i sin maximal strömförbrukning staten, men denna minskning innebär en straffavgift överföring /mottagning genomströmning av terminalen. Minskningen är notuniform för alla terminaler där trafiken utgör en förutsägbart beteende vinna mest. Uppskattningar av övre gränserna för tid untilthe nästa sändning eller mottagning är mer exakta om de görs tar som indata information om interarrival gånger tidigare paket.

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  • 277. Csaszar, Andras
    et al.
    Enyedi, Gabor
    Retveri, Gabor
    Hidell, Markus
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Sjödin, Peter
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Converging the evolution of router architectures and IP networks2007Ingår i: IEEE Network, ISSN 0890-8044, E-ISSN 1558-156X, Vol. 21, nr 4, s. 8-14Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Although IP is widely recognized as the platform for next-generation converged networks, unfortunately, it is heavily burdened by its heritage of almost 30 years. Nowadays, network operators must devote significant resources to perform essential tasks, such as traffic engineering, policy enforcement, and security. In this article, we argue that one of the principal reasons for this is the way control and forwarding planes are interspersed in IP networks today. We review the architectural. developments that led to the current situation, and we reason that centralization of network control functionality can constitute a solution to the pressing problems of the contemporary Internet.

  • 278.
    da Silva, Carlos Natalino
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Chiaraviglio, Luca
    Idzikowski, Filip
    Wosinska, Lena
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Datavetenskap, Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Datavetenskap, Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Joint Optimization of Failure Management Costs, Electricity Costs, and Operator Revenue in Optical Core Networks2017Ingår i: IEEE Transactions on Green Communications and Networking, ISSN 2473-2400, Vol. PP, nr 99Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We focus on the problem of maximizing profitability in an optical core network by acting on the power states of Optical Line Amplifiers (OLAs) and Line Cards (LCs) operating under varying traffic. Specifically, the profitability metric considered in this work takes into account the electricity costs of OLAs and LCs, the failure management costs derived from the application of power states to the network devices, and the operator revenue. After proving that all terms of the considered profitability function are deeply inter-correlated, we formulate the optimization problem of maximizing the network profitability in an optical core network with multi-period traffic. By solving the proposed formulation on a realistic scenario, we show that it is possible to wisely trade between the considered costs and revenue, and achieve higher network profitability than in the case in which the single terms are considered in isolation, e.g., only electricity consumption or only Failure Management Costs (FMC).

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  • 279.
    da Silva, Carlos Natalino
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Yayimli, Aysegul
    Istanbul University of Technology.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Furdek, Marija
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Assessing the effects of physical layer attacks on content accessibility and latency in optical CDNs2017Ingår i: 19th International Conference on Transparent Optical Networks (ICTON), Girona, Spain: IEEE conference proceedings, 2017, artikel-id 8024993Konferensbidrag (Refereegranskat)
    Abstract [en]

    Content Delivery Networks (CDNs) are a major enabler of large-scale content distribution for Internet applications. Many of these applications require high bandwidth and low latency for a satisfactory user experience, e.g., cloud gaming, augmented reality, tactile Internet and vehicular communications. Replication is one of the most prominent solutions to meet the requirements of latency-sensitive applications. However, infrastructure disruptions can greatly degrade the performance of such applications, or even cease their proper execution. The extent of degradation can be exacerbated by malicious attackers that target the critical elements of the CDN physical infrastructure to disconnect or severely degrade services.

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  • 280.
    da Silva, Carlos Natalino
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Yayimli, Aysegul
    Istanbul University of Technology.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Furdek, Marija
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Content Accessibility in Optical Cloud Networks Under Targeted Link Cuts2017Ingår i: 2017 21st International Conference on Optical Network Design and Modeling, ONDM 2017 - Conference Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, artikel-id 7958546Konferensbidrag (Refereegranskat)
    Abstract [en]

    One of the key enablers of the digital society is a highly reliable information infrastructure that can ensure resiliency to a wide range of failures and attacks. In cloud networks, replicas of various content are located at geographically distributed data centers, thus inherently enhancing cloud network reliability through diversification and redundancy of user accessibility to the content. However, cloud networks rely on optical network infrastructure which can be a target of deliberate link cuts that may cause service disruption on a massive scale. This paper investigates the dependency between the extent of damage caused by link cuts and a particular replica placement solution, as a fundamental prerequisite of resilient cloud network design that lacks systematic theoretical quantification and understanding. To quantify the vulnerability of optical cloud networks based on anycast communication to targeted link cuts, we propose a new metric called Average Content Accessibility (ACA). Using this metric, we analyze the impact of the number and the placement of content replicas on cloud network resiliency and identify the best and the worst case scenarios for networks of different sizes and connectivity. We evaluate the efficiency of simultaneous and sequential targeted link cuts, the latter reassessing link criticality between subsequent cuts to maximize disruption. Comparison with Average Two-Terminal Reliability (A2TR), an existing robustness measure for unicast networks, shows great discrepancy in the vulnerability results, indicating the need for new measures tailored to anycast-based networks.

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  • 281.
    Dahlberg, Christian
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Liu, Zhicheng
    KTH, Skolan för elektro- och systemteknik (EES). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Pradini, Aidilla
    KTH, Skolan för elektro- och systemteknik (EES). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    A Techno-Economic Framework of Spectrum Combining for Indoor Capacity Provisioning2013Ingår i: 2013 IEEE 24th International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), IEEE conference proceedings, 2013, s. 2759-2763Konferensbidrag (Refereegranskat)
    Abstract [en]

    Spectrum combining refers to utilizing multiple types of spectrum authorization options for a wireless network. The approach is considered as an essential ingredient of high-capacity provision in the coming years. This paper presents a techno-economic framework to analyze capacity and cost of different spectrum combining options. We focus on indoor environments where the traffic demand is expected to be extremely demanding. We describe various spectrum options such as licence-exempt, light licensing, and licensed shared access (LSA). Then, we compare various combinations of these options with increasing traffic demand over time. In terms of capacity provisioning, this framework is based on the idea that spectrum combining must be done at the right time, that is when the existing deployment can no longer satisfy capacity demand. For the cost analysis, most relevant cost drivers are included in a cost structure which becomes the backbone of this framework. The proposed framework can help network providers determine the most cost-effective spectrum acquisition strategy which can meet capacity demand in indoor environments.

  • 282.
    Dandugula, Chaitanya
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Networking for Smart Meters2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    "Smart grid" avser i allmänhet en klass av teknik föra system elleverans till 21: a århundradet, med hjälp av datorbaserade fjärrkontroll och automation. Med den ökande efterfrågan på energi, är effektiv användning av de tillgängliga energiresurser blir alltmer en viktig fråga över hela världen. Smart grid är ett steg i den riktningen. Forskning i Europeiska unionen och USA för närvarande pågår för att modernisera befintliga och åldrande transmissionsnätet och effektivisera användningen av el.

    En typisk elnätet består av två större enheter - de allmännyttiga företaget och \distribution control system"(DCS). El genereras vid verktyget företaget och DCS ansvarar för distributionen av el till enskilda hem / konsumenter. En smart meter (SM) är en elektronisk apparat som mäter elförbrukning på konsumentens lokaler och ger ökad information till elbolaget. \Data concentration unit"(DCU) är en enhet fungerar som ett kommunikationsnav insamling och kodning av data från flera smarta mätare i ett område och vidarebefordra data till elbolaget. Syftet med detta projekt är att utforma ett nätverk för att säkra kommunikationen mellan SM och DCU i ett smart mätning nätverksmiljö.

    Mätaren uppgifter som lämnas från SM till DCU är mycket känslig och i händerna på en angripare, kan avslöja viktig personlig information om en individ. Följaktligen är det av som mest betydelse för att skydda de mätdata som sänds från SM: en. å andra sidan styrsignaler överförs från DCU till SM och behöver skydd för att hindra av obehöriga signaler (dvs en inkräktare kan personifiera DC och skicka ut styrsignaler till SM). Därför SM och DCU ska bestyrkas av varandra och godkänts och data och / eller styrsignaler utväxlas mellan dem ska vara krypterad.

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  • 283.
    Dannerud, Sara
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Sårbarheter i routrar och switchar2008Självständigt arbete på grundnivå (yrkesexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Det finns många olika källor där man kan få information om sårbarheter i routrar och switchar. Mängden information gör det dock svårt att på ett enkelt sätt ta reda på vilka tillverkare som drabbas och vilken typ av sårbarheter man hittar i nätverksutrustning. Därmed är det också svårt att veta hur man ska skydda sin utrustning mot attacker.

    I detta examensarbete analyseras ett antal befintliga sårbarheter i routrar och switchar. Dessa sårbarheter har valts ut genom att i National Vulnerability Database söka på orden ”router” och ”switch”. Målet med analysen är att svara på frågorna vem, vad och varför när det gäller sårbarheter i routrar och switchar.

    Examensarbetet beskriver vilka tillverkare som drabbas av sårbarheter, vilka typer av sårbarheter som är vanligast i routrar och switchar och varför sårbarheterna har uppstått. Utifrån detta dras slutsatser om vad man som användare ska göra för att undvika attacker mot sin utrustning. I arbetet beskrivs också hur tillverkarna väljer att hantera de sårbarheter som finns i deras produkter.

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  • 284.
    Daoud, Nahir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Interference Mitigation in Coexisting WLANs2005Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Wired Local Area Network (WLAN) is a popular infrastructure today where it’s mostly used for indoor environments.  WLAN is easy to install for different applications, it’s easy to configure and the cost is less than the Wired LAN infrastructure.  The WLAN operates in the unlicensed, shared frequency bands where there are variety of signals such as microwave ovens, cordless telephones, Wireless Personal Area Networks(WPANs).  The growing popularity of different wireless devices operating in the unlicensed band increases the level of mutual interference from one to another, and causes a reduced QoS for all of them.

    The focus of this thesis is to investigate two WLANs that share the same frequency band.  The two WLANs coexist in the same geographical area and therefore will interfere with each other.  The task of this thesis is to investigate if adaptive antennas can improve the performance of coexisting WLANs and allow them, to share the same geographical area.  The benefit of adaptive antennas compared with the omnidirectional antenna is that they concentrate the main energy on one certain direction or point.  By doing so adaptive antennas are able to give the user or AP higher antenna gain and at the same time reduce the interference in other directions.  The adaptive antennas have also a long range coverage compared with the omnidirectional, for the most cases it will lead to a improvement of the network but in this thesis will it have a negative influence through higher generated interference between the users.

    The obtained results showed that the adaptive antenna models improved the networks QoS in terms of throughput and network separation at certain distances.  Also showed that when the networks came very near each other the adaptive antenna models lost there advantage over the omnidirectional antenna.

  • 285. Darrell, T. J.
    et al.
    Yeh, T.
    Tollmar, Konrad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Photo-based mobile deixis system and related techniques2004Patent (Övrig (populärvetenskap, debatt, mm))
  • 286. Darrell, Trevor
    et al.
    Tollmar, Konrad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Bentley, Frank
    Checka, Neal
    Morency, Loius-Phillipe
    Rahimi, Ali
    Oh, Alice
    Face-Responsive Interfaces: From Direct Manipulation to Perceptive Presence2002Ingår i: Proceedings of the 4th international conference on Ubiquitous Computing, ACM Press, 2002, s. 135-151Konferensbidrag (Refereegranskat)
    Abstract [en]

    Systems for tracking faces using computer vision have recently become practical for human-computer interface applications. We are developing prototype systems for face-responsive interaction, exploring three different interface paradigms: direct manipulation, gazemediated agent dialog, and perceptually-driven remote presence. We consider the characteristics of these types of interactions, and assess the performance of our system on each application. We have found that face pose tracking is a potentially accurate means of cursor control and selection, is seen by users as a natural way to guide agent dialog interaction, and can be used to create perceptually-driven presence artefacts which convey real-time awareness of a remote space.

  • 287.
    Darwis, Darwis
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Implementation and Analysis of VoIP CPE Management System using TR-0692008Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Customer Premises Equipment (CPE) skötseln är undervärderad av CPE försäljarna och tjänste leverantörerna meddans det faktiskt är en av de mest viktiga aspekterna för att tillförsäkra hög quality of service. Många personer tror fortfarande att CPE skötseln är det samma som att sköta ett nätverk. Så, de använder Simple Network Management Protocol (SNMP) för att sköta deras CPE:er. Emellertid, SNMP ensamt var inte tänkt att skala eller att ge stöd vid försörjning av typer av tjänster som internet tjänst leverantörer måste stödja idag.

    Den här avhandlingen framhäver det väsentliga med CPE skötsel, hur det implementeras vid användande av TR-069; ett CPE skötsel protocol definerat av DSL forum, och hur detta administrations system kan användas för att sköta VoIP tjänster. Tilläggande så kommer avhandligen att jämföra TR-069 och SNMP för att bestämma vilken av dem som är mer lämplig för CPE administration. En intressant sammanfattning är att meddans TR-069 har några fördelar över SNMP för att sköta tjänster hellre än att enkelt sköta enheten, dessa fördelar är inte så stora som man trott från början. Dessutom, TR-069 ser inte ut att kunna övervinna problemet med privatägd (användande av privat MIB) information som SNMP har demonstrerat.

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  • 288.
    De Andrade, Marilet
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Skubic, Björn
    Ahmed, Jawwad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Enhanced IPACT: solving the over-granting problem in long-reach EPON2013Ingår i: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 54, nr 2, s. 137-146Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we address an issue referred to as "over-granting problem", which is inherent in the existing dynamic bandwidth allocation algorithms for Ethernet-based Passive Optical Networks (EPON), in particular when deployed for multi-threaded scheme in long-reach scenario. In order to solve this problem we design a scheme for the algorithm of Interleaved Polling with Adapted Cycle Time (IPACT) with the limited service discipline. We evaluate the proposed scheme through simulations for single-thread and double-thread cases and demonstrate that, the network performance can be significantly improved by our solution in terms of average delay, jitter, and throughput.

  • 289. De Moor, K.
    et al.
    Andrén, B.
    Guo, Yi
    KTH. Acreo Swedish ICTAB, Sweden.
    Brunnström, K.
    Wang, Kun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab). Acreo Swedish ICTAB, Sweden.
    Drott, A.
    Hermann, D.
    Influence of high ambient illuminance and display luminance on readability and subjective preference2015Ingår i: Proceedings of SPIE - The International Society for Optical Engineering, 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Many devices, such as tablets, smartphones, notebooks, fixed and portable navigation systems are used on a (nearly) daily basis, both in in- and outdoor environments. It is often argued that contextual factors, such as the ambient illuminance in relation to characteristics of the display (e.g., surface treatment, screen reflectance, display luminance...) may have a strong influence on the use of such devices and corresponding user experiences. However, the current understanding of these influence factors is still rather limited. In this work, we therefore focus in particular on the impact of lighting and display luminance on readability, visual performance, subjective experience and preference. A controlled lab study (N=18) with a within-subjects design was performed to evaluate two car displays (one glossy and one matte display) in conditions that simulate bright outdoor lighting conditions. Four ambient luminance levels and three display luminance settings were combined into 7 experimental conditions. More concretely, we investigated for each display: (1) whether and how readability and visual performance varied with the different combinations of ambient luminance and display luminance and (2) whether and how they influenced the subjective experience (through self-reported valence, annoyance, visual fatigue) and preference. The results indicate a limited, yet negative influence of increased ambient luminance and reduced contrast on visual performance and readability for both displays. Similarly, we found that the self-reported valence decreases and annoyance and visual fatigue increase as the contrast ratio decreases and ambient luminance increases. Overall, the impact is clearer for the matte display than for the glossy display. 

  • 290.
    Debernardi, Nicolas
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Jäger,, Markus
    Laneri, Jean-Christophe
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Sraj, Malek
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Lungaro, Pietro
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Services Provisioning and Terminal Cooperation in User-Deployed Networks2006Ingår i: IEEE International Symposium on Personal, Indoor, and Mobile Radio Communications workshops, ISSN 2166-9570, E-ISSN 2166-9589Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Exploiting high-speed user-deployed Access Points (APs) in public infrastructures has been proposed as one of the candidate solutions for reducing the cost of future radio access. A disadvantage is that, due to lack of deployment coordination, these types of network are likely to provide only partial coverage. For this reason, the set of services that could be successfully provided in these networks might be rather limited. In this paper we present a novel framework for modeling non-interactive " infotainment" services with different degrees of "time criticality", and utilize it for investigating the user service perception in "spotty" coverage networks. In order to hide the infrastructure sparsity to the end users, the terminals are assumed equipped with software agents that can "opportunistically" pre-fetch information, on behalf of their users. This can be done when in contact with an AP, or, through a peer-to-peer file exchange with other terminal agents that have previously accessed the same information. In this paper, for different service types, the relationship between AP density and service perception is investigated. Furthermore, the impact of peer-to-peer terminal cooperation is evaluated in respect to both infrastructure requirements and content access delay. The results show that already with moderate AP densities, user-deployed networks deliver acceptable service perception, especially for services with low time criticality. Furthermore, whenever a "critical" mass of users shares common interests, the adoption of a peer-to-peer exchange strategy brings the significant gains of infrastructure reduction and/or improved service perception.

  • 291.
    Derakhshanno, Homayoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Voice over IP over GPRS2008Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    VoIP tekniken har blivit en rådande teknik numera på grund av dess lägre kostnader och mervärdestjänster som erbjuds jämfört med traditional telefoni. Samtidigt som tendensen mot mer tillgänglig trådlöst internet har underlättat och därmed driver mera studier inom dessa områden. Den allt mer utbredda användningen av avancerade mobiltelefoner och handdatorer numera har lett till ökat behov av att använda VoIP tekniken för dessa mobila utrustningar är alltmer kännbar. För att möjliggöra användadet av VoIP tekniken så behöver vi först och främst utvärdera dagens existerande teknologier för att stödja iden och för det andra måste vi kunna implementera en mjukvara vilket kan erbjuda olika typer av tjänster för slutanvändaren.

    För att kunna använda en IP-baserad tjänst på GSM teknologin så måste vi använda oss utan GPRS tjänster som tillhandahålls av GSM opratörer. I detta examens arbete kommer vi att utvärdera VoIP tjänster på GPRS när det gäller kvalitet och möjligheter. Därefter kommer vi att Portning en VoIP mjukvara till en handdator (utrustad med GSM sim-kort) vilket har windows Mobile operativsystemet som erbjuder en rad olika tjänster.

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  • 292.
    Devlic, Alisa
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab).
    On Optimization of Quality of User Experience and Wireless Network Bandwidth in Video Content Delivery2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Mobile video content today generates more than half of the mobile data traffic.The increasing popularity of mobile video on demand services poses great challenges to mobile operators and content providers. Frontmost, how to reduce the mobile video traffic load, while delivering high quality video content to mobile users without perceived quality degradations for the same (or cheaper) price? Battery lifetime represents another key factor of a user’s Quality of Experience(QoE). A lot of device energy is consumed by mobile network signalling and data transmission over new generation mobile communication systems. This thesis focuses on: (1) reducing the size of the video that is delivered to the enduser in the maximum achievable video quality, thus optimizing the wireless network bandwidth and the user-perceived QoE, and (2) reducing the energy consumption of a mobile device that is associated to data transfer over the radio interface, thus increasing the device’s battery lifetime. The main contributions have been given in providing the Over-the-Top video optimization and delivery schemes and recommendations on tuning their parameters in order to minimize the bandwidth and energy consumption of mobile video delivery, while maximizing the predictable user-perceived QoE. By preventing the video to be prefetched on low data rates and tuning the datarate threshold according to statistical properties of available data rates, we show that 20-70% of energy cost can be reduced by opportunistic prefetching, depending on the user’s pattern of available data rates. The data rate values ordered in time that have a large amount of serial correlation and low noise variance, or low average valueand high peak-to-mean ratio, are likely to yield the highest energy gains from content prefetching. Moreover, we show that energy gains are the largest when the threshold data rate is set close to an average data rate, due to the highest availability of data rates around this value, and for longer sleep time between the prefetching periods, which increases the probability of moving away from the areas with low data rates. Next, we focus on QoE-aware mobile video delivery solutions that are more bandwidth efficient without compromising the user-perceived video quality. They deliver a video over a varying data rate channel that is optimized for viewing on a mobile device in the highest perceptual video quality that can be achieved in the given video and network conditions. An optimized video consists of short segments in the minimum resolutions that satisfy the target perceptual video quality and have up to 60% reduced size compared to the video in the corresponding fixed video resolution, without perceptible quality difference. The delivery is performed by on demand download, context-aware prefetching, or in real time using the QoE-aware adaptive video streaming that runs over Dynamic Adaptive video Streaming over HTTP (DASH). By limiting the maximum bitrates of the requested video segments and using the remaining throughput to prefetch optimized video segments in advance of playout, we show that QoE-aware adaptive video streaming maintains a more stable perceptual video quality than DASH despite the fluctuations of the channel bandwidth, while using fewer number of bits, which improves a user-perceived QoE. The results of this thesis can help operators and content providers to reduce their costs and provide more content to their users at the same (or cheaper) price.

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  • 293.
    Devlic, Alisa
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Graf, A.
    Barone, P.
    Evaluation of context distribution methods via Bluetooth and WLAN: Insights gained while examining Battery Power Consumption2008Ingår i: MobiQuitous 2008 - 5th International ICST Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services, 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    In a traditional context-aware system, most context information is local to a device. However, we may need access to context information from outside the device. Increasingly mobile electronic devices are equipped with Bluetooth and/or WLAN network interfaces. Both of these technologies enable ad hoc discovery & networking. In this paper we evaluate the use of these technologies for context distribution within a local area (i.e., limited to a single hop). Using Bluetooth, we begin by discovering devices using Bluetooth's discovery protocol, collect their context information, create an XML file containing this information, and distribute this file to all discovered devices, such that every device now has the same context information. Next we perform the same discovery, collect, and distribute functions, but using WLAN. In each case we have performed the cycle of operations starting with a fully charged battery and continuing until the device was not able to utilize the selected wireless interface any longer. Finally we compare both approaches to context distribution in terms of battery power consumption. We observe that Bluetooth consumes 2-6 times more energy for transmission of a 1MB file to two devices than to discover these two devices. Furthermore, the transfer of this file is two times slower than WLAN, and we must unicast this file to each device. Multicasting via WLAN proved to be less energy consuming than the Bluetooth transmission, if data is to be sent to more than three users. In addition, the energy to discover 2 devices along with their services using Bluetooth consumed 52 times more energy than to receive the same amount of data via a WLAN multicast. Thus, this paper shows that it is more energy efficient to distribute context knowledge to other devices, than having each device learn this information itself. Finally, we give equations for calculating the battery power consumption of transmitting data using any protocol that runs over Bluetooth or over WLAN.

  • 294.
    Devlic, Alisa
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab).
    Kamaraju, Pavan
    Lungaro, Pietro
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab).
    Segall, Zary
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab).
    Tollmar, Konrad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab).
    QoE-aware optimization for video delivery and storage2015Ingår i: 2015 IEEE 16th International Symposium on "A World of Wireless, Mobile and Multimedia Networks" (WoWMoM) 2015, Boston, MA, USA, 2015, s. 1-10Konferensbidrag (Refereegranskat)
    Abstract [en]

    The explosive growth of Over-the-top (OTT) online video strains capacity of operators’ networks, which severely threatens video quality perceived by end users. Since video is very bandwidth consuming, its distribution costs are becoming too high to scale with network investments that are required to support the increasing bandwidth demand. Content providers and operators are searching for solutions to reduce this video traffic load, without degrading their customers’ perceived Quality ofExperience (QoE). This paper proposes a method that can programmatically optimize video content for desired QoE accordingto perceptual video quality and device display properties, while achieving bandwidth and storage savings for content providers, operators, and end users. The preliminary results obtained with Samsung Galaxy S3 phone show that up to 60% savings can be achieved by optimizing movies without compromising the perceptible video quality, and up to 70% for perceptible, but not annoying video quality difference. Tailoring video optimization to individual user perception can provide seamless QoE delivery across all users, with a low overhead (i.e., 10%) required to achieve this goal. Finally, two applications of video optimization: QoE-aware delivery and storage, are proposed and examined.

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  • 295.
    Devlic, Alisa
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab).
    Kamaraju, Pavan
    Lungaro, Pietro
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab).
    Segall, Zary
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab).
    Tollmar, Konrad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab).
    Towards QoE-aware adaptive video streaming2016Ingår i: 2015 IEEE 23rd International Symposium on Quality of Service (IWQoS), IEEE, 2016, s. 75-76, artikel-id 7404713Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes a novel QoE-aware adaptive video streaming method that enhances the viewing experience on mobile devices and reduces cellular network bandwidth consumed by Dynamic Adaptive Streaming over HTTP (DASH) by considering perceptual video quality and data rate channel conditions in the bitrate adaptation process. By streaming an optimized video for the particular video quality and channel conditions toa mobile device, we can improve the worst video qualities causedby DASH streaming and reduce quality variations using fewer number of bits.

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  • 296.
    Devlic, Alisa
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab).
    Lungaro, Pietro
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Kamaraju, Pavan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab).
    Segall, Zary
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Tollmar, Konrad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Energy consumption reduction via context-aware mobile video pre-fetching2012Ingår i: Proceedings - 2012 IEEE International Symposium on Multimedia, ISM 2012, IEEE , 2012, s. 261-265Konferensbidrag (Refereegranskat)
    Abstract [en]

    The arrival of smartphones and tablets, along with a flat rate mobile Internet pricing model have caused increasing adoption of mobile data services. According to recent studies, video has been the main driver of mobile data consumption, having a higher growth rate than any other mobile application. However, streaming a medium/high quality video files can be an issue in a mobile environment where available capacity needs to be shared among a large number of users. Additionally, the energy consumption in mobile devices increases proportionally with the duration of data transfers, which depend on the download data rates achievable by the device. In this respect, adoption of opportunistic content pre-fetching schemes that exploit times and locations with high data rates to deliver content before a user requests it, has the potential to reduce the energy consumption associated with content delivery and improve the user's quality of experience, by allowing playback of pre-stored content with virtually no perceived interruptions or delays. This paper presents a family of opportunistic content pre-fetching schemes and compares their performance to standard on-demand access to content. By adopting a simulation approach on experimental data, collected with monitoring software installed in mobile terminals, we show that content pre-fetching can reduce energy consumption of the mobile devices by up to 30% when compared to the on demand download of the same file, with a time window of 1 hour needed to complete the content prepositioning.

  • 297.
    Devlic, Alisa
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab).
    Lungaro, Pietro
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Segall, Zary
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Tollmar, Konrad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Mobile Service Laboratory (MS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Evaluation of energy profiles for mobile video prefetching in generalized stochastic access channels2014Ingår i: Mobile and Ubiquitous Systems: Computing, Networking, and Services: 10th International Conference, MOBIQUITOUS 2013, Tokyo, Japan, December 2-4, 2013, Revised Selected Papers, Springer, 2014, s. 209-223Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper evaluates the energy cost reduction of Over-The-Top mobile video content prefetching in various network conditions. Energy cost reduction is achieved by reducing the time needed to download content over the radio interface by prefetching data on higher data rates, compared to the standard on demand download. To simulate various network conditions and user behavior, a stochastic access channel model was built and validated using the actual user traces. By changing the model parameters, the energy cost reduction of prefetching in different channel settings was determined, identifying regions in which prefetching is likely to deliver the largest energy gains. The results demonstrate that the largest gains (up to 70%) can be obtained for data rates with strong correlation and low noise variation. Additionally, based on statistical properties of data rates, such as peak-to-mean and average data rate, prefetching strategy can be devised enabling the highest energy cost reduction that can be obtained using the proposed prefetching scheme.

  • 298. Di Giglio, A.
    et al.
    Schiano, M.
    Ruffini, M.
    Payne, D.
    Doran, N.
    Achouche, M.
    Jensen, R.
    O’Sullivan, B.
    Pfeiffer, T.
    Bonk, R.
    Rohde, H.
    Talli, G.
    Yin, X.
    Wessaly, R.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Montalvo, J.
    Towards the distributed core for ubiquitous superfast broadband optical access2014Ingår i: 2014 European Conference on Networks and Communications (EuCNC), 2014, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we describe recent architectural and technological advances of the end to end optical network architecture proposed by the DISCUS project (the DIStributed Core for unlimited bandwidth supply for all Users and Services). The two main targets of DISCUS are the principle of equivalence in the access and the reduction of optical-to-electronic conversions in the metro-core network. Technological advances and techno-economic evaluation of Long-Reach Passive Optical Networks (LR-PON), as well as the optimal metro-core node architecture and the required network control plane framework are reported. Network infrastructure sharing challenges are also discussed.

  • 299.
    Di Pascale, Emanuele
    et al.
    CTVR, Trinity College, Ireland .
    Payne, David B.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Ruffini, Marco
    Locality-Aware Peer-to-Peer Multimedia Delivery Over Next-Generation Optical Networks2014Ingår i: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 6, nr 9, s. 782-792Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The increasing success of multimedia services poses a serious challenge to both network operators and service providers. Traditional copper-based access technologies are being replaced by fiber-to-the-X (FTTX) deployments in order to meet this increasing bandwidth demand of individual users. However, the growing traffic volume in the access segment may overload the existing aggregation part of the network, therefore creating a bandwidth bottleneck in the core. To address this problem the traffic should be kept as much as possible in the access network, taking advantage of the high-capacity fiber infrastructure. Since multimedia traffic is dominating the network, locality-aware approaches to video content distribution can represent a good solution. In this work, we propose and evaluate a network-managed, peer-to-peer based caching scheme for multimedia distribution. Our results show that such a system is able to reduce core traffic compared to the traditional content delivery network (CDN) based strategies, while at the same time decreasing the overall power consumption of the network and offering cost-saving opportunities for operators.

  • 300.
    Di, Shuang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    USB Attached Network Performance: Uplink Performance2009Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Fler och fler människor över hela världen använder ett USB-modem för att ansluta tillInternet. Detta gäller i synnerhet i Sverige, som har den största 3G-täckning i Europa.Jämförbar med fast bredband, med hjälp av ett 3G USB-modemet är en underbar upplevelseför kunden. Allt var som helst vi kan använda vår mobiltelefon är en plats som vi hartillgång till Internet, även om vi färdas i ett tåg, promenad i en park, eller sitter på stranden.Detta gör att arbeta på resande fot mycket enklare. Men kunderna inte vet om nätetgenomströmning, fördröjning, och kostnaden för anslutning passar deras behov. Dessutomfinns det också en fråga om tid att ansluta till nätverket när det inte har funnits några trafikför en tid. Men den genomströmning, fördröjning och "tid för att ansluta" när du använderett modem för att ansluta till ett trådlöst nätverk beror på flera faktorer. I denna avhandlingkommer vi att undersöka dessa faktorer. Mer specifikt avhandlingen analyserar i detaljeffekterna av att använda en USB bifogade nätverkskort, för att få större förståelse för ettsådant gränssnitt nätverk prestanda. Vi har valt att fokusera på upplänk, eftersom detförväntas ha låg kapacitet och det har inte fått lika mycket uppmärksamhet som denerlänkning prestanda.

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