Ändra sökning
Avgränsa sökresultatet
40414243444546 2101 - 2150 av 2282
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 2101.
    Xu, Tianhua
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Optik (Stängd 20120101).
    Jacobsen, G.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Li, J.
    Wang, Ke
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Optik (Stängd 20120101).
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Variable-step-size LMS adaptive filter for digital chromatic dispersion compensation in PDM-QPSK coherent transmission system2009Ingår i: 2009 International Conference on Optical Instruments and Technology: Optical Systems and Modern Optoelectronic Instruments, SPIE - International Society for Optical Engineering, 2009, s. 75062I-Konferensbidrag (Refereegranskat)
    Abstract [en]

    High bit rates optical communication systems pose the challenge of their tolerance to linear and nonlinear fiber impairments. Digital filters in coherent optical receivers can be used to mitigate the chromatic dispersion entirely in the optical transmission system. In this paper, the least mean square adaptive filter has been developed for chromatic equalization in a 112-Gbit/s polarization division multiplexed quadrature phase shift keying coherent optical transmission system established on the VPIphotonics simulation platform. It is found that the chromatic dispersion equalization shows a better performance when a smaller step size is used. However, the smaller step size in least mean square filter will lead to a slower iterative operation to achieve the guaranteed convergence. In order to solve this contradiction, an adaptive filter employing variable-step-size least mean square algorithm is proposed to compensate the chromatic dispersion in the 112-Gbit/s coherent communication system. The variable-step-size least mean square filter could make a compromise and optimization between the chromatic dispersion equalization performance and the algorithm converging speed. Meanwhile, the required tap number and the converged tap weights distribution of the variable-step-size least mean square filter for a certain fiber chromatic dispersion are analyzed and discussed in the investigation of the filter feature.

  • 2102.
    Xu, Tianhua
    et al.
    Univ Warwick, Coventry CV4 7AL, W Midlands, England..
    Jacobsen, Gunnar
    RISE Acreo AB, SE-16440 Stockholm, Sweden..
    Li, Jie
    RISE Acreo AB, SE-16440 Stockholm, Sweden..
    Leeson, Mark
    Univ Warwick, Coventry CV4 7AL, W Midlands, England..
    Popov, Sergei
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Dynamic physical layer equalization in optical communication networks2018Ingår i: Optoelectronics and Advanced Materials Rapid Communications, ISSN 1842-6573, E-ISSN 2065-3824, Vol. 12, nr 5-6, s. 292-298Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In optical transport networks, signal lightpaths between two terminal nodes can be different due to current network conditions. Thus the transmission distance and accumulated dispersion in the lightpath cannot be predicted. Therefore, the adaptive compensation of dynamic dispersion is necessary in such networks to enable flexible routing and switching. In this paper, we present a detailed analysis on the adaptive dispersion compensation using the least-mean-square (LMS) algorithm in coherent optical communication networks. It is found that the variable-step-size LMS equalizer can achieve the same performance with a lower complexity, compared to the traditional LMS algorithm.

  • 2103.
    Xu, Yuzhe
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Real Time Scheduling in LTE for Smart Grids2012Ingår i: 5th International Symposium on Communications Control and Signal Processing, ISCCSP 2012, IEEE , 2012, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    The latest wireless network, 3GPP Long Term Evolution (LTE), is considered to be a promising solution for smart grids because it provides both low latency and large bandwidth. However, LTE was not originally intended for smart grids applications, where data generated by the grid have specific delay requirements that are different from traditional data or voice communications. In this paper, the specific requirements imposed by a smart grids on the LTE communication infrastructure is first determined. The latency offered by the LTE network to smart grids components is investigated and an empirical mathematical model of the distribution of the latency is established. It is shown by experimental results that with the current LTE up-link scheduler, smart grid latency requirements are not always satisfied and that only a limited number of components can be accommodated. To overcome such a deficiency, a new scheduler of the LTE medium access control is proposed for smart grids. The scheduler is based on a mathematical linear optimization problem that considers simultaneously both the smart grid components and common user equipments. An algorithm for the solution to such a problem is derived based on a theoretical analysis. Simulation results based on this new scheduler illustrate the analysis. It is concluded that LTE can be effectively used in smart grids if new schedulers are employed for improving latency.

  • 2104.
    Xu, Yuzhe
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Hossein, Shokri-Ghadikolaei
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Distributed Association and Relaying in Millimeter Wave NetworksIngår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248Artikel i tidskrift (Refereegranskat)
  • 2105.
    Xu, Yuzhe
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Hossein, Shokri-Ghadikolaei
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Dynamic Distributed Association with Fairness in Millimeter Wave NetworksManuskript (preprint) (Övrigt vetenskapligt)
  • 2106.
    Xu, Yuzhe
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Shokri Ghadikolaei, Hossein
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Adaptive Distributed Association in Time-Variant Millimeter Wave Networks2019Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 18, nr 1, s. 459-472Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The underutilized millimeter-wave (mm-wave) band is a promising candidate to enable extremely high data rate communications in future wireless networks. However, the special characteristics of the mm-wave systems such as high vulnerability to obstacles (due to high penetration loss) and to mobility (due to directional communications) demand a careful design of the association between the clients and access points (APs). This challenge can be addressed by distributed association techniques that gracefully adapt to wireless channel variations and client mobilities. We formulated the association problem as a mixed-integer optimization aiming to maximize the network throughput with proportional fairness guarantees. This optimization problem is solved first by a distributed dual decomposition algorithm, and then by a novel distributed auction algorithm where the clients act asynchronously to achieve near-to-optimal association between the clients and APs. The latter algorithm has a faster convergence with a negligible drop in the resulting network throughput. A distinguishing novel feature of the proposed algorithms is that the resulting optimal association does not have to be re-computed every time the network changes (e.g., due to mobility). Instead, the algorithms continuously adapt to the network variations and are thus very efficient. We discuss the implementation of the proposed algorithms on top of existing communication standards. The numerical analysis verifies the ability of the proposed algorithms to optimize the association and to maintain optimality in the time-variant environments of the mm-wave networks.

  • 2107. Xu, Z.
    et al.
    Archambault, E.
    Tremblay, C.
    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).
    Belanger, M. P.
    Littlewood, P.
    1+1 dedicated optical-layer protection strategy for filterless optical networks2014Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 18, nr 1, s. 98-101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We propose a dedicated optical-layer protection strategy for filterless optical networks offering a 100% protection ratio by introducing a limited number of wavelength selective components at selected intermediate nodes. A comparison with conventional active photonic switching networks is presented. The results show that the proposed 1+1 protection for filterless networks exhibits a clear cost advantage at similar wavelength usage compared to active switching solutions.

  • 2108. Xue, Q.
    et al.
    Fang, X.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Beam management for millimeter wave beamspace MU-MIMO systems2018Ingår i: 2017 IEEE/CIC International Conference on Communications in China, ICCC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2018, Vol. 2018-January, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    Millimeter wave (mmWave) communication has attracted increasing attention as a promising technology for 5G networks. One of the key architectural features of mmWave is the use of massive antenna arrays at both the transmitter and the receiver sides. Therefore, by employing directional beamforming (BF), both mmWave base stations (MBSs) and mmWave users (MUEs) are capable of supporting multi-beam simultaneous transmissions. However, most researches have only considered a single beam, which means that they do not make full potential of mmWave. In this context, in order to improve the performance of short-range indoor mmWave networks with multiple reflections, we investigate the challenges and potential solutions of downlink multi-user multi-beam transmission, which can be described as a high-dimensional (i.e., beamspace) multi-user multiple-input multiple-output (MU-MIMO) technique, including multi-user BF training, simultaneous users' grouping, and multi-user multi-beam power allocation. Furthermore, we present the theoretical and numerical results to demonstrate that beamspace MU-MIMO compared with single beam transmission can largely improve the rate performance of mmWave systems.

  • 2109.
    Yaghoubi, Forough
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Agile, Resilient and Cost-efficient Mobile Backhaul Networks2017Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The exponentially increasing traffic demand for mobile services requires innovative solutions in both access and backhaul segments of 5th generation (5G) mobile networks. Although, heterogeneous networks (HetNets) are a promising solution for the wireless access, the backhaul segment has received considerably less attention and falls short in meeting the stringent requirements of 5G in terms of capacity and availability.

    HetNets together with mobility requirements motivate the use of microwave backhauling that supports fiber-like capacity with millimeter-wave communications. However, higher carrier frequencies are subject to weather disturbances like rain that may substantially degrade the network throughput. To mitigate this effect, we develop a fast and accurate rain detection algorithm that triggers a network-layer strategy, i.e., rerouting. The results show that with small detection error the network throughput increases while posing small overhead on the network.

    The rain impact can be alleviated by centralized rerouting under the software defined networking paradigm. However, careless reconfiguration may impose inconsistency that leads to a significant temporary congestion and limits the gain of rerouting. We propose a consistency-aware rerouting framework by considering the cost of reconfiguration. At each time, the centralized controller may either take a rerouting or no-rerouting decision in order to minimize the total data loss. We use a predictive control algorithm to provide such an online sequence of decisions. Compared to the regular rerouting, our proposed approach reduces the throughput loss and substantially decreases the number of reconfigurations.

    In the thesis we also study which backhaul option is the best from a techno-economic perspective. We develop a comprehensive framework to calculate the total cost of ownership of the backhaul segment and analyze the profitability in terms of cash flow and net present value. The results highlight the importance of selecting proper backhaul solution to increase profitability.

  • 2110.
    Yaghoubi, Forough
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS.
    Furdek, Marija
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS.
    Rostami, A.
    Öhlén, P.
    Wosinska, Lena
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS.
    Reliable topology design of wireless networks under correlated failures2018Ingår i: 2018 IEEE International Conference on Communications (ICC), Institute of Electrical and Electronics Engineers (IEEE), 2018, artikel-id 8422496Konferensbidrag (Refereegranskat)
    Abstract [en]

    Inherent vulnerability of wireless backhauling to random fluctuations of the wireless channel complicates the design of reliable backhaul networks. In the presence of such disturbances, network reliability can be improved by providing redundant paths between given source and destination. Many studies deal with modifying and designing the network topology to meet the reliability requirements in a cost- efficient manner. However, these studies ignore the correlation among link failures, such as those caused by rain. Consequently, the resulting topology design solutions may fail to satisfy the network reliability requirements under correlated failure scenarios. To address this issue, this paper studies the design of reliable wireless backhaul networks under correlated failures with focus on rain fading. We consider green-field topology design and brown-field topology upgrade scenarios with the objective to minimize the total cost of wireless links added to meet the target reliability requirement in the presence of correlated link failures. We propose a new model to formulate the spatial correlation using pairwise joint probability distribution of rain attenuation between different links. This model is applied to consider the link- wise correlation along individual paths, as well as the correlation among the multiple redundant paths from the source to the destination node of a traffic flow. We formulate the problem as a quadratic integer program, which is NP-hard, and develop a heuristic algorithm to find near-optimal solutions. Performance evaluation shows that correlation-aware design improves the resiliency under rain disturbance at a slightly increased cost.

  • 2111.
    Yaghoubi, Forough
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS.
    Furdek, Marija
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS.
    Rostami, Ahmad
    Ericsson Res, Networks Orchestrat & Automat, S-16483 Kista, Sweden..
    Ohlen, Peter
    Ericsson Res, S-16483 Kista, Sweden..
    Wosinska, Lena
    KTH, Skolan för industriell teknik och management (ITM), Lärande.
    Consistency-Aware Weather Disruption-Tolerant Routing in SDN-Based Wireless Mesh Networks2018Ingår i: IEEE Transactions on Network and Service Management, ISSN 1932-4537, E-ISSN 1932-4537, Vol. 15, nr 2, s. 582-595Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wireless network solutions, a dominant enabling technology for the backhaul segment, are susceptible to weather disturbances that can substantially degrade network throughput and/or delay, compromising the stringent 5G requirements. These effects can be alleviated by centralized rerouting realized by software defined networking architecture. However, careless frequent reconfigurations can lead to inconsistencies in the network states due to asynchrony between different switches, which can create congestion and limit the rerouting gain. The aim of this paper is to minimize the total data loss during rain disturbance by proposing an algorithm that decides on the timing, the sequence, and the paths for rerouting of network flows considering the imposed congestion during reconfiguration. At each time sample, the central controller decides whether to adopt the optimal routes at a switching cost, defined as the imposed congestion, or to keep using existing, sub-optimal routes at a throughput loss. To find optimal solutions with minimal data loss in a static scenario, we formulate a dynamic programming problem that utilizes perfect knowledge of rain attenuation for the whole rain period. For dynamic scenarios with unknown future rain attenuation, we propose an online consistency-aware rerouting algorithm, called consistency-aware rerouting with prediction (CARP), which uses the temporal correlation of rain fading to estimate future rain attenuation. Simulation results on synthetic and real networks validate the efficiency of our CARP algorithm, substantially reducing data loss and increasing network throughput with a fewer number of rerouting actions compared to a greedy and a regular rerouting benchmarking approaches.

  • 2112.
    Yaghoubi, Forough
    et al.
    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).
    Rostami, Ahmad
    Ericsson AB.
    Öhlén, Peter
    Ericsson AB.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Consistency-aware Weather Disruption-tolerant Routing in SDNbased Wireless Mesh Networks2017Ingår i: IEEE TNSM Special Issue on Advances in Management of Softwarized NetworksArtikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Although, wireless solutions continue to be a dominant enabling technology in the future backhaul  segment, they are susceptible to weather disturbances that may substantially degrade network throughput, or delay, compromising the 5G requirements.  These  effects  can  be  alleviated  by centralized rerouting realized by software defined networking (SDN) architecture. However, careless frequent reconfigurations may lead to inconsistencies in network states due to asynchrony between different switches, which may create  congestion and limit the gain of frequent rerouting.  In  this  paper, we focus on the rerouting process during rain disturbance considering the minimum total congestion imposed  during  the  update  of  routing  tables as a switching cost. At each time sample, the central controller has the possibility to adopt the optimal routes at a switching cost or to keep using previous routes at the expense of a throughput loss due to route sub- optimality. To find optimal solutions with minimal data loss in a static scenario, we formulate a dynamic programming problem that utilizes perfect knowledge of the rain attenuation for the whole rain period (off-line policy with full knowledge). For dynamic scenarios where the future rain attenuation data cannot be known, we propose an online consistency-aware rerouting algorithm, called optimal control action with prediction (OCAP), which uses the temporal correlation of rain fading to estimate the future rain attenuation. Simulation results on synthetic and real networks validate the efficiency of our OCAP algorithm, substantially reducing congestion and increasing network throughput with a fewer number of rerouting actions compared to benchmarks approaches.

  • 2113.
    Yaghoubi, Forough
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Mahloo, Mozghan
    Ericsson AB.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Farias, Fabricio de Souza
    Universidade Federal do Pará.
    Costa, João Crisóstomo Weyl Albuquerque
    Universidade Federal do Pará.
    A Techno-Economic Framework for 5G Transport Networks2017Ingår i: Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Wireless heterogeneous networks (HetNets) are a cost- and an energy-efficient alternative to provide high capacity to end users in the future 5G communication systems. However, the transport segment of a radio access network (RAN) poses a big challenge in terms of cost and energy consumption. In fact, if not planned properly its resulting high cost might limit the benefits of using small cells and impact the revenues of mobile network operators. Therefore, it is essential to be able to properly assess the economic viability of different transport techonolgies as well as their impact on the cost and profitability of a HetNets deployment (i.e., RAN + transport).

    This paper first presents a general and comprehensive techno-economic framework able to assess not only the total cost of ownership (TCO) but also the business viability of a HetNets deployment. It then applies it to the specific case study of a backhaul-based transport segment. In the evaluation work two technology options for the transport network are considered (i.e., microwave and fiber) assuming both a homogeneous (i.e., macro cells only) and a HetNet deployments. Our results demonstrate the importance of selecting the right technology and deployment strategy in order not to impact the economic benefits of a HetNet deployment. Moreover, the results also reveal that a deployment solution with the lowest TCO does not always lead to the highest profit.  

  • 2114.
    Yajie, Li I.
    et al.
    KTH. Beijing University of Posts and Telecommunications, China.
    Zhao, Y.
    Zhang, J.
    Xiaosong, Y. U.
    Jing, R.
    Data analysis-based autonomic bandwidth adjustment in software defined multi-vendor optical transport networks2017Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, nr 24, s. 29835-29846Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Network operators generally provide dedicated lightpaths for customers to meet the demand for high-quality transmission. Considering the variation of traffic load, customers usually rent peak bandwidth that exceeds the practical average traffic requirement. In this case, bandwidth provisioning is unmetered and customers have to pay according to peak bandwidth. Supposing that network operators could keep track of traffic load and allocate bandwidth dynamically, bandwidth can be provided as a metered service and customers would pay for the bandwidth that they actually use. To achieve cost-effective bandwidth provisioning, this paper proposes an autonomic bandwidth adjustment scheme based on data analysis of traffic load. The scheme is implemented in a software defined networking (SDN) controller and is demonstrated in the field trial of multi-vendor optical transport networks. The field trial shows that the proposed scheme can track traffic load and realize autonomic bandwidth adjustment. In addition, a simulation experiment is conducted to evaluate the performance of the proposed scheme. We also investigate the impact of different parameters on autonomic bandwidth adjustment. Simulation results show that the step size and adjustment period have significant influences on bandwidth savings and packet loss. A small value of step size and adjustment period can bring more benefits by tracking traffic variation with high accuracy. For network operators, the scheme can serve as technical support of realizing bandwidth as metered service in the future.

  • 2115.
    Yajnanarayana, Vijaya
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dwivedi, Satyam
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Multi Detector Fusion of Dynamic TOA hstimation using Kalman Filter2016Ingår i: 2016 IEEE International Conference on Communications (ICC), Institute of Electrical and Electronics Engineers (IEEE), 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we propose fusion of dynamic time of arrival (TOA) from multiple low complexity detectors like energy detectors operating at sub-Nyquist rate through Kalman filtering. We show that by having a multi-channel sub-Nyquist receiver with each channel having an energy detector can match the performance of a single channel digital receiver with matched filter. We derive analytical expression for number of sub-Nyquist energy detector channels needed to achieve the performance of digital implementation with matched filter and demonstrate in simulation the validity of our analytical approach. Results indicate that number of energy detectors needed will he high at low SNRs and converge to a constant number as the SNR increases. We also study the performance of the proposed strategy using IEEE 802.15.4a CM1 multipath channel model and show in simulation that two sub-Nyquist detectors are sufficient to match the performance of digital matched filter.

  • 2116.
    Yalew, Sileshi Demesie
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS. Universidade de Lisboa, Portugal.
    Maguire Jr., Gerald Q.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Correia, Miguel
    Universidade de Lisboa, Portugal.
    Light-SPD: a platform to prototype secure mobile applications2016Ingår i: Proceedings of the 1st ACM Workshop on Privacy-Aware Mobile Computing (PAMCO '16), New York, NY, USA: Association for Computing Machinery (ACM), 2016, s. 11-20Konferensbidrag (Refereegranskat)
    Abstract [en]

    Securely storing sensitive personal data is critical for protecting privacy. Currently, many persons use smartphones to store their private data. However, smartphones suffer from many security issues. To overcome this situation, the PCAS project is designing a secure personal storage device called the Secure Portable Device (SPD), to be attached to a smartphone for securely storing sensitive personal data. However, this device is unavailable, closed, and expensive to deploy for prototyping applications. We propose a platform that emulates the SPD and the smartphone using a board with an ARM processor with the TrustZone security extension. This platform is open, inexpensive, and secure. A payment application is used as an example to show the platform's capabilities. As a proof-of-concept, we implemented this platform and provide a performance evaluation using a i.MX53 board.

  • 2117. Yan, L.
    et al.
    Fiorani, Matteo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Muhammad, Ajmal
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Tornatore, M.
    Agrell, E.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Network performance trade-off in optical spatial division multiplexing data centers2017Ingår i: 2017 Optical Fiber Communications Conference and Exhibition, OFC 2017 - Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    We propose close-to-optimal network resource allocation algorithms for modular data centers using optical spatial division multiplexing. A trade-off between the number of established connections and throughput is identified and quantified.

  • 2118. Yang, B.
    et al.
    Gong, Y.
    Hong, X.
    Chen, Jiajia
    Heatsink topology based optical interconnect for datacenters2017Ingår i: Optics InfoBase Conference Papers, OSA - The Optical Society , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    We propose an optical interconnect architecture based on heatsink topology to enhance reliability for large-scale datacenters. The experimental demonstration has been carried out to verify the transmission performance of the proposed architecture.

  • 2119. Yang, B.
    et al.
    He, H.
    Hu, Xiaoming
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Detecting community structure in networks via consensus dynamics and spatial transformation2017Ingår i: Physica A: Statistical Mechanics and its Applications, ISSN 0378-4371, E-ISSN 1873-2119, Vol. 483, s. 156-170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a novel clustering algorithm for community detection, based on the dynamics towards consensus and spatial transformation. The community detection problem is translated to a clustering problem in the N-dimensional Euclidean space by three stages: (1) the dynamics running on a network is emulated to a procedure of gas diffusion in a finite space; (2) the pressure distribution vectors are used to describe the influence that each node exerts on the whole network; (3) the similarity measures between two nodes are quantified in the N-dimensional Euclidean space by k-Nearest Neighbors method. After such steps, we could merge clusters according to their similarity distances and show the community structure of a network by a hierarchical clustering tree. Tests on several benchmark networks are presented and the results show the effectiveness and reliability of our algorithm.

  • 2120.
    Yang, Bo
    et al.
    Wuhan Univ Technol, Sch Automat, Wuhan 430070, Hubei, Peoples R China..
    Cheng, Weizheng
    Wuhan Univ Technol, Sch Automat, Wuhan 430070, Hubei, Peoples R China..
    Hu, Xiaoming
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Zhu, Chao
    Wuhan Univ Technol, Sch Automat, Wuhan 430070, Hubei, Peoples R China..
    Yu, Xin
    Wuhan Univ Technol, Sch Automat, Wuhan 430070, Hubei, Peoples R China..
    Li, Xu
    Wuhan Univ Technol, Sch Automat, Wuhan 430070, Hubei, Peoples R China..
    Huang, Tao
    Wuhan Univ Technol, Sch Automat, Wuhan 430070, Hubei, Peoples R China..
    Seeking community structure in networks via biogeography-based optimization with consensus dynamics2019Ingår i: Physica A: Statistical Mechanics and its Applications, ISSN 0378-4371, E-ISSN 1873-2119, Vol. 527, artikel-id 121188Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Uncovering the community structure hidden in networks is crucial for understanding the function of networks. In this paper, an algorithm of biogeography-based optimization with consensus dynamics for community detection is proposed. The problems of seeking community structures in networks are exquisitely embedded into the framework of biogeography-based optimization. Hence the community structure unveiled in such an evolutionary and global manner is corresponding to the habitat with maximum modularity. We present a dynamical framework for generating initial distribution of solutions for the evolutionary process using consensus dynamics, which gives a reasonably good estimate of the community structure based on the topological information. Thereof, the proposed dynamical method of initialization promotes the efficiency of optimal solution search significantly, compared with the traditional random initialization. Then, the obtained partition is refined using biogeography-based optimization. In addition, a preferential selection strategy for generating the new solutions is developed based on local network topology. Furthermore, we also proposed an adaptive mutation operator that enhances the exploration ability of our evolutionary algorithm. The experimental results on both artificial random and real-world networks indicate the effectiveness and reliability of our algorithm. These findings shed new light on the role played by topological knowledge of networks extracted from consensus dynamics in the evolving optimization processes when finding complex mesoscale structures in networks such as community structure.

  • 2121. Yang, Bo
    et al.
    Shen, Yanyan
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Guan, Xinping
    Threshold-based Multichannel Access with Energy Constraint2010Ingår i: 2010 IEEE International Conference on Communications, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper considers multiaccess control for the uplink in orthogonal-frequency-division-multiple-access (OFDMA) wireless networks. To avoid extensive information exchange with the access point in centralized approaches, we propose a distributed threshold-based scheme, where each user accesses multiple channels simultaneously based on a comparison between measured channel gains and a channel gain threshold. Each user will adapts its channel gain threshold based on local measurements of collision on each channel and the energy consumption for channel contention. The problem is formulated as a constrained non-cooperative game. We show existence and uniqueness of the Nash equilibrium. A gradient-based algorithm is proposed to update the channel gain threshold. Furthermore, the convergence of this algorithm is proved. In addition, for heterogeneous systems, our proposed scheme can maintain multiuser diversity gains considering the time-varying channel gain and energy consumption. Compared with peer distributed OFDMA schemes and random channel selection algorithms, our proposed schemes reduce overhead and achieve a higher throughput.

  • 2122.
    Yang, Dekun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Investigation of a new integration test environment: Facilitating offline debugging of Hardware-in-the-Loop2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    I fordonsindustrin ställs stora krav på avancerad automatiserad testning. För att utvärdera Electronic Control Units (ECUs) används så kallade Hardware-In-the-Loop-system (HIL) för att simulera den omkringliggande hårdvaran. Detta möjliggör enklare samt säkrare testning av ECU-komponenterna än vid traditionell fysisk testning. Med hjälp av HIL kan ECUs testas innan en fullskalig produktion sätts igång. Då HIL-system vanligtvis utvecklas för ett brett användningsområde kan det ta tid att skräddarsy dem för ett specifikt system. Ett annat viktigt problem vi ställs inför är skillnaderna mellan HIL-systemet och testmiljön, då testfallen förväntas att användas en längre tid utan förändringar. Vidare är HIL-system kostsamma. Det anses vara varken praktiskt eller ekonomiskt att låta HIL-system enbart användas av testare.

    Scanias RESI-grupp använder en klient-server-arkitektur för att åstadkomma flexibilitet HIL-systemet körs på serversidan medan testarna arbetar på klientsidan. Den här typen av arkitektur öppnar upp för olika implementationer på klient- samt serversida, förutsatt att samma kommunikationsprotokoll används. En nackdel med den nuvarande lösningen är att HIL-systemet inte alltid finns tillgängligt när testarna vill felsöka deras programskript. Testarna vill hitta en lösning där det går att utföra felsökningen lokalt, utan tillgång till servrar.

    För att kunna lösa problemet undersöktes först vilka programmeringsspråk som används inom industrin. Undersökningen visar på att det finns inget programmeringsspråk som är idealt för alla ändamål. Vidare utvecklades en ny testmiljö som tillhandahåller testlägena "Dummy Mode" samt "Mat Mode". Testmiljön kan användas för att validera programskript på grund- och logiknivå utan att kommunicera mot servrar. Resultatet visar att "Dummy Mode" detekterar upp till 99.3% av enklare typ av fel än motsvarande 81.3% i nuvarande testmiljön. Genom att reproducera och återanvända resultat av HIL-systemet kan “Mat Mode” identifiera logikfel samt ge en bättre indikation om vad felen innebär. Generellt sätt kan den föreslagna testmiljön visa på ett bättre användande av HIL, som gör hela systemet mer effektivt och produktivt.

  • 2123.
    Yang, Guang
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Haenggi, Martin
    Univ Notre Dame, Dept Elect Engn, Notre Dame, IN 46556 USA..
    Xiao, Ming
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Traffic Allocation for Low-Latency Multi-Hop Networks With Buffers2018Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 66, nr 9, s. 3999-4013Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For buffer-aided tandem networks consisting of relay nodes and multiple channels per hop, we consider two traffic allocation schemes, namely local allocation and global allocation, and investigate the end-to-end latency of a file transfer. We formulate the problem for generic multi-hop queuing systems and subsequently derive closed-form expressions of the end-to-end latency. We quantify the advantages of the global allocation scheme relative to its local allocation counterpart, and we conduct an asymptotic analysis on the performance gain when the number of channels in each hops increases to infinity. The traffic allocations and the analytical delay performance are validated through simulations. Furthermore, taking a specific two-hop network with millimeter-wave (mm-wave) as an example, we derive lower bounds on the average end-to-end latency, where Nakagami-m fading is considered. Numerical results demonstrate that, compared with the local allocation scheme, the advantage of global allocation grows as the number of relay nodes increases, at the expense of higher complexity that linearly increases with the number of relay nodes. It is also demonstrated that a proper deployment of relay nodes in a linear mm-wave network plays an important role in reducing the average end-to-end latency, and the average latency decays as the mm-wave channels become more deterministic. These findings provide insights for designing multi-hop mm-wave networks with low end-to-end latency.

  • 2124.
    Yang, Guang
    et al.
    KTH.
    Xiao, Ming
    KTH.
    Blockage robust millimeter-wave networks2017Ingår i: Science China Information Sciences, ISSN 1674-733X, E-ISSN 1869-1919, Vol. 60, nr 8, artikel-id 080307Artikel i tidskrift (Refereegranskat)
  • 2125.
    Yang, Guang
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap.
    Interference statistics of regular ring-structured networks with 60 GHz directional antennas2017Ingår i: 2017 IEEE International Conference on Communications, Institute of Electrical and Electronics Engineers (IEEE), 2017, artikel-id 7996400Konferensbidrag (Refereegranskat)
    Abstract [en]

    To overcome the severe path loss and provide higher spectral efficiency for 60 GHz wireless communications, highly directional antennas, which indicate high antenna gains, are widely employed. In this work, we focus on the trade-off between the beamwidth of directional antennas and the interference produced by random concurrent transmissions, in terms of two important statistics, i.e., the expectation and variance. A specific regular network is considered, which consists of multi-layer rings, and a typical receiver with a fixed orientation is placed in the network center.We derive closed-form expressions of interference statistics associated with the beamwidth, which are followed by upper and lower bounds. In addition, we demonstrate that the performance gain provided by directional antennas approximately grows in the fashion of the reciprocal of beamwidth, and an approximation for the expectation of signal-to-interference-and-noise ratio (SINR) is also presented. Numerical results show that, analytic expressions coincide with simulations, and derived bounds are valid. The benefits of utilizing directional antennas are quantified and verified. Furthermore, the impacts of the factors, such as path loss exponent and side-lobe gain, are also studied, comprehensively.

  • 2126.
    Yang, Guang
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Gross, James
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Al-Zubaidy, Hussein
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Huang, Yongming
    Delay and Backlog Analysis for 60 GHz Wireless Networks2016Ingår i: 2016 IEEE Global Communications Conference, GLOBECOM 2016 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2016, artikel-id 7841725Konferensbidrag (Refereegranskat)
    Abstract [en]

    To meet the ever-increasing demands on higher throughput and better network delay performance, 60 GHZ networking is proposed as a promising solution for the next generation of wireless communications. To successfully deploy such networks, its important to understand their performance first. However, due to the unique fading characteristic of the 60 GHz channel, the characterization of the corresponding service process, offered by the channel, using the conventional methodologies may not be tractable. In this work, we provide an alternative approach to derive a closed-form expression that characterizes the cumulative service process of the 60 GHz channel in terms of the moment generating function (MGF) of its instantaneous channel capacity. We then use this expression to derive probabilistic upper bounds on the backlog and delay that are experienced by a flow traversing this network, using results from the MGF-based network calculus. The computed bounds are validated using simulation. We provide numerical results for different networking scenarios and for different traffic and channel parameters and we show that the 60 GHz wireless network is capable of satisfying stringent quality-of-Service (QoS) requirements, in terms of network delay and reliability. With this analysis approach at hand, a larger scale 60 GHz network design and optimization is possible.

  • 2127.
    Yang, Ping
    et al.
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
    Xiao, Yue
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
    Xiao, Ming
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Guan, Yong Liang
    Nanyang Technol Univ, Sch Elect & Elect Engn, Singapore 639798, Singapore..
    Li, Shaoqian
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
    Xiang, Wei
    James Cook Univ, Coll Sci & Engn, Cairns, Qld 4878, Australia..
    Adaptive Spatial Modulation MIMO Based on Machine Learning2019Ingår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 37, nr 9, s. 2117-2131Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we propose a novel framework of low-cost link adaptation for spatial modulation multiple-input multiple-output (SM-MIMO) systems-based upon the machine learning paradigm. Specifically, we first convert the problems of transmit antenna selection (TAS) and power allocation (PA) in SM-MIMO to ones-based upon data-driven prediction rather than conventional optimization-driven decisions. Then, supervised-learning classifiers (SLC), such as the K-nearest neighbors (KNN) and support vector machine (SVM) algorithms, are developed to obtain their statistically-consistent solutions. Moreover, for further comparison we integrate deep neural networks (DNN) with these adaptive SM-MIMO schemes, and propose a novel DNN-based multi-label classifier for TAS and PA parameter evaluation. Furthermore, we investigate the design of feature vectors for the SLC and DNN approaches and propose a novel feature vector generator to match the specific transmission mode of SM. As a further advance, our proposed approaches are extended to other adaptive index modulation (IM) schemes, e.g., adaptive modulation (AM) aided orthogonal frequency division multiplexing with IM (OFDM-IM). Our simulation results show that the SLC and DNN-based adaptive SM-MIMO systems outperform many conventional optimization-driven designs and are capable of achieving a near-optimal performance with a significantly lower complexity.

  • 2128.
    Yang, Xi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    The Use of One-Time Password and RADIUS Authentication in a GSS-API Architecture2006Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    IETF GSS-API är ett applikationsgränssnitt (API) som tillhandahåller distribuerade säkerhetstjänster för autentisering och datakonfidentialitet oberoende av den underliggande säkerhetarkitekturen. Applikationer som skrivs mot detta API kan på detta sätt flyttas eller porteras utan att västentligen skrivas om. GSS-API stöds av ett flertal undrliggande säkerhetsarkitekturer som tex Kerberos 5, Windows NTLM och PKI. API har också sk bindings för "C" och Java. I dagsläget finns det dock ingen lösning som baseras på engångslösenord.

    Denna magisteruppsats har som mål att undersöka möjligheten att använda engångslösenord tillsammans med RADIUS för att implementera en ny GSS-API mechanism. Denna uppsats presenterar ett förslag för hur RADIUS och engångslösenord kan användas för att säkra kommunikationen mellan två GSS-API entiteter.

    Den föreslagna mekanismen kan också användas för att förbättra säkerheten för användarautentisering och möjliggöra en övergång från statiska lösenord till stark autentisering.

  • 2129.
    Yang, Yanpeng
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    A study on the deployment and cooperative operation of ultra-dense networks2017Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The traffic volume in wireless communication has grown dramatically in the last decade and is predicted to keep increasing in the future. In this thesis, we focus on the densification dimension for capacity improvement, which has been proved to be the most effective in the past. The current gain of network densification mainly comes from cell splitting, thereby serving more user equipments (UEs) simultaneously. This trend will decelerate as base station (BS) density gets closer to or even surpass UE density which forms an ultra-dense network (UDN). Thus, it is crucial to understand the behavior of ultra-densification for future network provisioning.

     

    We start from comparing the effectiveness of densification with spectrum expansion and multi-antenna systems. Our findings show that deploying more BSs provides a substantial gain in sparse network but the gain decreases progressively in a UDN. The diminishing gain appears in a UDN make us curious to know if there exists a terminal on the way of densification. Such uncertainty leads to the study on the asymptotic behavior of densification. We incorporate a sophisticated bounded dual-slope path loss model and practical UE densities in our analysis. By using stochastic geometry, we derive the expressions and prove the convergence of the coverage probability of a typical UE and network area spectral efficiency (ASE). Considering the large portion of dormant BSs in a UDN, it is an interesting question whether we can utilize these dormant BSs to improve system performance is an interesting question. To this end, we employ joint transmission (JT) techniques into a UDN. Two types of cooperation schemes are investigated: non-coherent JT and coherent JT depending on the availability of channel state information (CSI). Our results reveal that non-coherent JT is not beneficial in a UDN while coherent JT are able to increase UE spectral efficiency (SE) depending on the environmental parameters.

  • 2130.
    Yang, Yanpeng
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Ultra-Densification for Future Cellular Networks: Performance Analysis and Design Insights2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The traffic volume in wireless communication has grown dramatically in the lastdecade. Recent predictions indicate such data storm will be even more violent in theshort run. Potential solutions for accommodating the rapid traffic growth can besummed up into three categories: broadening the available bandwidth, improvingthe spectral efficiency, and densifying the infrastructure. In this thesis, we focuson the densification dimension which has been proven to be the most effectiveone in the past. The current gain of network densification mainly comes from cellsplitting, thereby serving more user equipment (UE) simultaneously. This trendwill decelerate as the base station (BS) density gets closer to or even surpassesthe UE density which forms an ultra-dense network (UDN). Thus, it is crucialto understand the behavior and design operations of ultra-densification in futurenetworks.

    An important question for future system design and operating strategy is whichelement is more effective than others. To this end, we start from comparing the effectivenessof densification with spectrum expansion and multi-antenna systems interms of meeting certain traffic demand. Our findings show that deploying more BSsprovides a substantial gain in sparse network but the gain decreases progressively ina UDN. Meanwhile, even with the same area throughput, different combinations ofindividual throughput and UE density lead to different requirements for resources.The diminishing gain appearing in UDNs makes us curious to know if there existsa terminal on the way of densification. Such uncertainty leads to the study onthe asymptotic behavior of densification. By incorporating a sophisticated boundeddual-slope path loss model and practical UE densities in our analysis, we present theasymptotic behavior of ultra-densification: the coverage probability and area spectralefficiency (ASE) have non-zero convergences in asymptotic regions unless theUE density goes to infinity (full load). Our results suggest that network densificationcannot always improve the UE performance or boost the network throughput.

    Next, we shift our focus to the operations of UDNs. We first study BS cooperationsin two UDN scenarios: homogeneous and heterogeneous UDNs which aredistinguished by BS types. In both cases, the cooperation rules become more complicatedthan those in traditional networks. Either channel state information (CSI) orextra delay information needs to be acquired in order to obtain cooperation gains.At last, we investigate the feasibility of applying random beamforming to initialaccess in millimeter-wave (mmWave) UDNs. To our surprise, the simple methodcan provide sufficient performance in both control and data plane, comparing withthe existing schemes. Therefore, it may be unnecessary to develop complex algorithmsfor initial access in future dense mmWave networks. The findings indicatethat UDN may complicate network operations while it may also facilitate the use ofsimple schemes. Our work provides insights into the understanding of the networkdensification and thus paves the way for the operational design of future UDNs.

  • 2131.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Hossein, Shokri-Ghadikolaei
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Fischione, Carlo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Petrova, Marina
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Ki Won, Sung
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Fast and Reliable Initial Access with Random Beamforming for mmWave NetworksManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Millimeter-wave (mmWave) communications rely on directional transmissions to overcome severe path loss. Nevertheless, the use of narrow beams complicates the initial access procedure and increase the latency as the transmitter and receiver beams should be aligned for a proper link establishment. In this paper, we investigate the feasibility of random beamforming for the cell-search phase of initial access. We develop a stochastic geometry framework to analyze the performance in terms of detection failure probability and expected latency of initial access as well as total data transmission. Meanwhile, we compare our scheme with the widely used exhaustive search and iterative search schemes, in both control plane and data plane. Numerical results show that, compared to the other two schemes, random beamforming can substantially reduce the latency of initial access with comparable failure probability in dense networks. We show that the gain of the random beamforming is more prominent in light traffics and low-latency services. Our work demonstrates that developing complex cell-discovery algorithms may be unnecessary in dense mmWave networks and thus shed new lights on mmWave network design.

  • 2132.
    Yang, Yanpeng
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Hossein, Shokri-Ghadikolaei
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Fischione, Carlo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Petrova, Marina
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Sung, Ki Won
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Reducing Initial Cell-search Latency in mmWave Networks2018Ingår i: INFOCOM 2018 - IEEE Conference on Computer Communications Workshops, IEEE conference proceedings, 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Millimeter-wave (mmWave) networks rely on directional transmissions, in both control plane and data plane, to overcome severe path-loss. Nevertheless, the use of narrow beams complicates the initial cell-search procedure where we lack sufficient information for beamforming. In this paper, we investigate the feasibility of random beamforming for cell-search. We develop a stochastic geometry framework to analyze the performance in terms of failure probability and expected latency of cell-search. Meanwhile, we compare our results with the naive, but heavily used, exhaustive search scheme. Numerical results show that, for a given discovery failure probability, random beamforming can substantially reduce the latency of exhaustive search, especially in dense networks. Our work demonstrates that developing complex cell-discovery algorithms may be unnecessary in dense mmWave networks and thus shed new lights on mmWave system design.

  • 2133.
    Yang, Yanpeng
    et al.
    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.
    Park, J.
    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.
    On the asymptotic behavior of ultra-densification under a bounded dual-slope path loss model2017Ingår i: European Wireless 2017 - 23rd European Wireless Conference, Institute of Electrical and Electronics Engineers (IEEE), 2017, artikel-id 8011320Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we investigate the impact of network densification on the performance in terms of downlink signal-to-interference (SIR) coverage probability and network area spectral efficiency (ASE). A sophisticated bounded dual-slope path loss model and practical user equipment (UE) densities are incorporated in the analysis, which have never been jointly considered before. By using stochastic geometry, we derive an integral expression along with closed-form bounds of the coverage probability and ASE, validated by simulation results. Through these, we provide the asymptotic behavior of ultra-densification. The coverage probability and ASE have non-zero convergence in asymptotic regions unless UE density goes to infinity (full load). Meanwhile, the effect of UE density on the coverage probability is analyzed. The coverage probability will reveal an U-shape for large UE densities due to interference fall into the near-field, but it will keep increasing for low UE densites. Furthermore, our results indicate that the performance is overestimated without applying the bounded dual-slope path loss model. The derived expressions and results in this work pave the way for future network provisioning.

  • 2134.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Park, Jihong
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    On the Asymptotic Behavior of Ultra-Densificationunder a Bounded Dual-Slope Path Loss ModelManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In this paper, we investigate the impact of networkdensification on the performance in terms of downlink signal-tointerference(SIR) coverage probability and network area spectralefficiency (ASE). A sophisticated bounded dual-slope path lossmodel and practical UE densities are incorporated in the analysis.By using stochastic geometry, we derive an integral expressionalong with closed-form bounds of the coverage probability andASE, validated by simulation results. Through these, we providethe asymptotic behavior of ultra-densification. The coverageprobability and ASE have non-zero convergence in asymptoticregions unless UE density goes to infinity (full load). Meanwhile,the effect of UE density on the coverage probability is analyzed.The coverage probability will suffer from decreasing with largeUE densities due to interference fall into the near-field, but it willkeep increasing with lower UE densites. Furthermore, we showthe performance is overestimated without applying the boundeddual-slope path loss model. Our study can give insights on efficientnetwork provisioning in the future.

  • 2135.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Shi, Lei
    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).
    On the Capacity of Wi-Fi System in TV White Space with Aggregate Interference Constraint2013Ingår i: Proceedings of the 2013 8th International Conference on Cognitive Radio Oriented Wireless Networks and Communications, CROWNCOM 2013, IEEE conference proceedings, 2013, s. 123-128Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we present a quantitative assessmentof the performance of a Wi-Fi like system in TV white space andcompare it with the traditional Wi-Fi system in the ISM band.Particular emphasis is given to the constraint on the aggregatesecondary interference on TV reception, which is regarded as thepremise of the link throughput analysis that followed. Numericalevaluation is performed over different scenarios where the TVreceive signal strength, number of unoccupied TV channels, userdensity are varied. Our results show that the primary interferenceconstraint has only significant impact on the secondary systemperformance in rural scenario with low TV receive signalstrength. In other cases, where higher transmit power does notguarantee better performance, the capacity of the system islimited by the secondary self-interference or collisions rather thanthe interference constraint. Therefore, efficient TV White Spaceutilization can be achieved by properly setting the secondarytransmit power adaptive to different environments.

  • 2136.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Park, J.
    Kim, S. -L
    Kim, K. S.
    Cooperative transmissions in ultra-dense networks under a bounded dual-slope path loss model2017Ingår i: 2017 European Conference on Networks and Communications (EuCNC), Institute of Electrical and Electronics Engineers (IEEE), 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    In an ultra-dense network (UDN) where there are more base stations (BSs) than active users, it is possible that many BSs are instantaneously left idle. Thus, how to utilize these dormant BSs by means of cooperative transmission is an interesting question. In this paper, we investigate the performance of a UDN with two types of cooperation schemes: Non-coherent joint transmission (JT) without channel state information (CSI) and coherent JT with full CSI knowledge. We consider a bounded dual-slope path loss model to describe UDN environments where a user has several BSs in the near-field and the rest in the far-field. Numerical results show that non-coherent JT cannot improve the user spectral efficiency (SE) due to the simultaneous increment in signal and interference powers. For coherent JT, the achievable SE gain depends on the range of near-field, the relative densities of BSs and users, and the CSI accuracy. Finally, we assess the energy efficiency (EE) of cooperation in UDN. Despite costing extra energy consumption, cooperation can still improve EE under certain conditions.

  • 2137.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Park, Jihong
    Kim, Seong-Lyun
    Kim, Kwang Soon
    Cooperative Transmissions in Ultra-Dense Networks under a Bounded Dual-Slope Path Loss ModelManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In an Ultra-dense network (UDN) where there aremore base stations (BSs) than active users, it is possible thatmany BSs are instantaneously left idle. Thus, how to utilizethese dormant BSs by means of cooperative transmission is aninteresting question. In this paper, we investigate the performanceof a UDN with two types of cooperation schemes: non-coherentjoint transmission (JT) without channel state information (CSI)and coherent JT with full CSI knowledge. We consider a boundeddual-slope path loss model to describe UDN environments wherea user has several BSs in the near-field and the rest in thefar-field. Numerical results show that non-coherent JT cannotimprove the user spectral efficiency (SE) due to the simultaneousincrement in signal and interference powers. For coherent JT, theachievable SE gain depends on the range of near-field, the relativedensities of BSs and users, and the CSI accuracy. Finally, weassess the energy efficiency (EE) of cooperation in UDN. Despitecosting extra energy consumption, cooperation can still improveEE under certain conditions.

  • 2138.
    Yang, Zhe
    et al.
    Dept. of Signal Processing Processing, Blekinge Institute of Technology.
    Khamit, Saltanat
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Mohammed, A.
    Dept. of Signal Processing Processing, Blekinge Institute of Technology.
    Larson, Peter
    Strategoc Dev., Affärsverken Karlskrona AB.
    A Comparative Study on Business Models of Municipal WirelessCities in US and Sweden2008Ingår i: 3rd IEEE/IFIP International Workshop on Business-driven IT Management, 2008. BDIM 2008, IEEE conference proceedings, 2008, s. 116-117Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we will explore the existing operational "business models" for municipal wireless networks in US and Sweden. Based on the current paradigms of the North-American public wireless networks, we will investigate an emerging wireless city concept in Sweden to analysis this new business concept in the existing field. We will look into the relationship of different actors in various business models of the wireless cities in our selected case studies. This paper will aim to demonstrate a number of key considerations when designing and managing the business model of Municipal wireless networks as business-driven and public utility-driven services.

  • 2139.
    Yanggratoke, Rerngvit
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Data-driven Performance Prediction and Resource Allocation for Cloud Services2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Cloud services, which provide online entertainment, enterprise resource management, tax filing, etc., are becoming essential for consumers, businesses, and governments. The key functionalities of such services are provided by backend systems in data centers. This thesis focuses on three fundamental problems related to management of backend systems. We address these problems using data-driven approaches: triggering dynamic allocation by changes in the environment, obtaining configuration parameters from measurements, and learning from observations. 

    The first problem relates to resource allocation for large clouds with potentially hundreds of thousands of machines and services. We developed and evaluated a generic gossip protocol for distributed resource allocation. Extensive simulation studies suggest that the quality of the allocation is independent of the system size for the management objectives considered.

    The second problem focuses on performance modeling of a distributed key-value store, and we study specifically the Spotify backend for streaming music. We developed analytical models for system capacity under different data allocation policies and for response time distribution. We evaluated the models by comparing model predictions with measurements from our lab testbed and from the Spotify operational environment. We found the prediction error to be below 12% for all investigated scenarios.

    The third problem relates to real-time prediction of service metrics, which we address through statistical learning. Service metrics are learned from observing device and network statistics. We performed experiments on a server cluster running video streaming and key-value store services. We showed that feature set reduction significantly improves the prediction accuracy, while simultaneously reducing model computation time. Finally, we designed and implemented a real-time analytics engine, which produces model predictions through online learning.

  • 2140.
    Yanggratoke, Rerngvit
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Telekommunikationssystem, TSLab.
    GPU Network Processing2010Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Nätverksteknik ansluter fler och fler människor runt om i världen. Det har blivit en viktig del av vårt dagliga liv. För att denna anslutning skall vara sömlös, måste nätet vara snabbt. Den snabba tillväxten i nätverkstrafiken och olika kommunikationsprotokoll sätter stora krav på processorer som hanterar all trafik. Befintliga lösningar på detta problem, t.ex. ASIC, FPGA, NPU, och TOE är varken kostnadseffektivt eller lätta att hantera, eftersom de kräver speciell hårdvara och anpassade konfigurationer. Denna avhandling angriper problemet på ett annat sätt genom att avlasta nätverks processningen till grafikprocessorer som sitter i vanliga pc-grafikkort. Avhandlingen främsta mål är att ta reda på hur GPU bör användas för detta. Avhandlingen följer fallstudie modell och de valda fallen är lager 2 Bloom filter forwardering och ``flow lookup'' i Openflow switch. Implementerings alternativ och utvärderingsmetodik föreslås för både fallstudierna. Sedan utvecklas och utvärderas en prototyp för att jämföra mellan traditionell CPU- och GPU-offload. Det primära resultatet från detta arbete utgör kriterier för nätvärksprocessfunktioner lämpade för GPU offload och vilka kompromisser som måste göras. Kriterier är inget inter-paket beroende, liknande processflöde för alla paket. och möjlighet att köra fler processer på ett paket paralellt. GPU offloading ger ökad fördröjning och minneskonsumption till förmån för högre troughput.

  • 2141.
    Yanggratoke, Rerngvit
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ahmed, Jawwad
    Ericsson Research, Sweden.
    Ardelius, John
    Swedish Institute of Computer Science (SICS), Sweden.
    Flinta, Christofer
    Ericsson Research, Sweden.
    Johnsson, Andreas
    Ericsson Research, Sweden.
    Gillblad, Daniel
    Swedish Institute of Computer Science (SICS), Sweden.
    Stadler, Rolf
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Predicting Real-time Service-level Metrics from Device Statistics2015Ingår i: IFIP/IEEE International Symposium on Integrated Network Management, IM 2015, Ottawa, Canada, IEEE Communications Society, 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    While real-time service assurance is critical for emerging telecom cloud services, understanding and predicting performance metrics for such services is hard. In this paper, we pursue an approach based upon statistical learning whereby the behavior of the target system is learned from observations. We use methods that learn from device statistics and predict metrics for services running on these devices. Specifically, we collect statistics from a Linux kernel of a server machine and predict client-side metrics for a video-streaming service (VLC). The fact that we collect thousands of kernel variables, while omitting service instrumentation, makes our approach service-independent and unique. While our current lab configuration is simple, our results, gained through extensive experimentation, prove the feasibility of accurately predicting client-side metrics, such as video frame rates and RTP packet rates, often within 10-15% error (NMAE), also under high computational load and across traces from different scenarios.

  • 2142.
    Yanggratoke, Rerngvit
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ahmed, Jawwad
    Ardelius, John
    Flinta, Christofer
    Johnsson, Andreas
    Gillblad, Daniel
    Swedish Institute of Computer Science (SICS), Sweden.
    Stadler, Rolf
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Predicting Real-time Service-level Metrics from Device Statistics2014Rapport (Övrigt vetenskapligt)
    Abstract [en]

    While real-time service assurance is critical for emerging telecom cloud services, understanding and predicting performance metrics for such services is hard. In this paper, we pursue an approach based upon statistical learning whereby the behavior of the target system is learned from observations. We use methods that learn from device statistics and predict metrics for services running on these devices. Specifically, we collect statistics from a Linux kernel of a server machine and predict client-side metrics for a video-streaming service (VLC). The fact that we collect thousands of kernel variables, while omitting service instrumentation, makes our approach service-independent and unique. While our current lab configuration is simple, our results, gained through extensive experimentation, prove the feasibility of accurately predicting client-side metrics, such as video frame rates and RTP packet rates, often within 10-15% error (NMAE), also under high computational load and across traces from different scenarios.

  • 2143.
    Yanggratoke, Rerngvit
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Ahmed, Jawwad
    Ardelius, John
    Flinta, Christofer
    Johnsson, Andreas
    Gillblad, Daniel
    Stadler, Rolf
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Predicting service metrics for cluster-based services using real-time analytics2015Ingår i: IFIP/IEEE 11th International Conference on Network and Service Management, CNSM 2015, Barcelona, Spain, November 9-13, 2015, IEEE conference proceedings, 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Predicting the performance of cloud services is intrinsically hard. In this work, we pursue an approach based upon statistical learning, whereby the behaviour of a system is learned from observations. Specifically, our testbed implementation collects device statistics from a server cluster and uses a regression method that accurately predicts, in real-time, client-side service metrics for a video streaming service running on the cluster. The method is service-agnostic in the sense that it takes as input operating-systems statistics instead of service-level metrics. We show that feature set reduction significantly improves prediction accuracy in our case, while simultaneously reducing model computation time. We also discuss design and implementation of a real-time analytics engine, which processes streams of device statistics and service metrics from testbed sensors and produces model predictions through online learning.

  • 2144.
    Yanggratoke, Rerngvit
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Ahmed, Jawwad
    Ardelius, John
    Flinta, Christoffer
    Johnsson, Andreas
    Gillblad, Daniel
    Stadler, Rolf
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    A service-agnostic method for predicting service metrics in real-timeManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    We predict performance metrics of cloud services using statistical learning, whereby the behavior of a system is learned from observations. Specifically, we collect device and network statistics from a cloud testbed and apply regression methods to predict, in real-time, client-side service metrics for video streaming and key-value store services. Our method is service agnostic in the sense that it takes as input operating-systems and network statistics instead of service-specific metrics. We show that feature set reduction significantly improves the prediction accuracy in our case, while simultaneously reducing model computation time. We find that the prediction accuracy decreases when, instead of a single service, both services run on the same testbed simultaneously or when the network quality on the path between the server cluster and the client deteriorates. Finally, we discuss the design and implementation of a real-time analytics engine, which processes streams of device statistics and service metrics from testbed sensors and produces model predictions through online learning.

  • 2145.
    Yanggratoke, Rerngvit
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Azfar, Abdullah
    Marval, María José Peroza
    Ahmed, Sharjeel
    Delay Tolerant Network on Android Phones: Implementation Issues and Performance Measurements2011Ingår i: Journal of Communications, ISSN 1796-2021, E-ISSN 1796-2021, Vol. 6, nr 6, s. 477-484Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many regions of the world do not have access to the Internet due to lack of proper communication infrastructure. Delay Tolerant Network (DTN) provides communication in a challenging network condition such as high communication delay and intermittent connectivity. DTN is a promising solution to solve lack of connectivity problems in developing regions such as rural areas. DTN works in a store-and-forward approach, where the data is stored in a server and forwarded to a suitable carrier. The android phones can be made DTN capable to become a carrier for DTN bundles. Android phone is one of the front runners as the DTN carrier because of its portability and increasing popularity. In this paper, we have described theimplementation of DTN on Android phone and the performance measurements including DTN bandwidth and battery consumption.

  • 2146.
    Yanggratoke, Rerngvit
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    El Hosary, Amira
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Selected Paper on Network and Cloud Analytics2016Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report reviews selected papers from the ones presented in the seminar on Network and Cloud Analytics since April 2015 till November 2015 (realm.sics.se). During this time period, the seminar discussed 43 papers that span different research disciplines, such as analytics for network management, network anomaly detection, large-scale machine learning, and learning under concept drift. From those papers, we select 13 papers that provide compelling contributions and possible extensions for future work. Additionally, we grouped the selected papers based on their problem area. For each selected paper, we identify the problem that the authors try to solve, major challenges that make the problem difficult, a proposed approach to solve the problem, and key contributions of the paper. Further, we show the limitations of the proposed method and suggest ideas for applying the paper to our research projects.

  • 2147.
    Yanggratoke, Rerngvit
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Kreitz, Gunnar
    Spotify.
    Goldmann, Mikael
    Spotify.
    Stadler, Rolf
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Predicting response times for the Spotify backend2012Rapport (Övrigt vetenskapligt)
    Abstract [en]

    We model and evaluate the performance of a distributed key-value storage system that is part of the Spotify backend. Spotify is an on-demand music streaming service, offering low-latency access to a library of over 16 million tracks and serving over 10 million users currently. We first present a simplified model of the Spotify storage architecture, in order to make its analysis feasible. We then introduce an analytical model for the distribution of the response time, a key metric in the Spotify service. We parameterize and validate the model using measurements from two different testbed configurations and from the operational Spotify infrastructure. We find that the model is accurate—measurements are within 11% of predictions—within the range of normal load patterns. We apply the model to what-if scenarios that are essential to capacity planning and robustness engineering. The main difference between our work and related research in storage system performance is that our model provides distributions of key system metrics, while related research generally gives only expectations, which is not sufficient in our case.

  • 2148.
    Yanggratoke, Rerngvit
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Kreitz, Gunnar
    KTH, Skolan för datavetenskap och kommunikation (CSC), Teoretisk datalogi, TCS. Spotify AB.
    Goldmann, Mikael
    Spotify AB.
    Stadler, Rolf
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fodor, Viktoria
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    On the performance of the Spotify backend2013Ingår i: Journal of Network and Systems Management, ISSN 1064-7570, E-ISSN 1573-7705Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We model and evaluate the performance of a distributed key-value storage system that is part of the Spotify backend. Spotify is an on-demand music streaming service, offering low-latency access to a library of over 20 million tracks and serving over 20 million users currently. We first present a simplified model of the Spotify storage architecture, in order to make its analysis feasible. We then introduce an analytical model for the distribution of the response time, a key metric in the Spotify service. We parameterize and validate the model using measurements from two different testbed configurations and from the operational Spotify infrastructure. We find that the model is accurate---measurements are within 11% of predictions---within the range of normal load patterns.In addition, we model the capacity of the Spotify storage system under different object allocation policies and find that measurements on our testbed are within 9% of the model predictions. The model helps us justify the object allocation policy adopted for Spotify storage system.

  • 2149.
    Yao, Yuan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Lu, Zhonghai
    KTH.
    INPG: Accelerating Critical Section Access with In-network Packet Generation for NoC Based Many-Cores2018Ingår i: 2018 IEEE International Symposium on High Performance Computer Architecture (HPCA), IEEE Computer Society, 2018, s. 15-26Konferensbidrag (Refereegranskat)
    Abstract [en]

    As recently studied, serialized competition overhead for entering critical section is more dominant than critical section execution itself in limiting performance of multi-threaded shared variable applications on NoC-based many-cores. We illustrate that the invalidation-acknowledgement delay for cache coherency between the home node storing the critical section lock and the cores running competing threads is the leading factor to high competition overhead in lock spinning, which is realized in various spin-lock primitives (such as the ticket lock, ABQL, MCS lock, etc.) and the spinning phase of queue spin-lock (QSL) in advanced operating systems. To reduce such high lock coherence overhead, we propose in-network packet generation (iNPG) to turn passive 'normal' NoC routers which only transmit packets into active 'big' ones that can generate packets. Instead of performing all coherence maintenance at the home node, big routers which are deployed nearer to competing threads can generate packets to perform early invalidation-acknowledgement for failing threads before their requests reach the home node, shortening the protocol round-trip delay and thus significantly reducing competition overhead in various locking primitives. We evaluate iNPG in Gem5 using PARSEC and SPEC OMP2012 programs with five different locking primitives. Compared to a state-of-the-art technique accelerating critical section access, experimental results show that iNPG can effectively reduce lock coherence overhead, expediting critical section access by 1.35x on average and 2.03x at maximum and consequently improving the program Region-of-Interest (ROI) runtime by 7.8% on average and 14.7% at maximum.

  • 2150. Yasoubi, A.
    et al.
    Hojabr, R.
    Takshi, H.
    Modarressi, M.
    Daneshtalab, Masoud
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik och Inbyggda System.
    CuPAN - high throughput on-chip interconnection for neural networks2015Ingår i: 22nd International Conference on Neural Information Processing, ICONIP 2015, Springer, 2015, s. 559-566Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we present a Custom Parallel Architecture for Neural networks (CuPAN). CuPAN consists of streamlined nodes that each node is able to integrate a single or a group of neurons. It relies on a high-throughput and low-cost Clos on-chip interconnection network in order to efficiently handle inter-neuron communication. We show that the similarity between the traffic pattern of neural networks (multicast-based multi-stage traffic) and topological characteristics of multi-stage interconnection networks (MINs) makes neural networks naturally suited to the MINs. The Clos network, as one of the most important classes of MINs, provide scalable low-cost interconnection fabric composed of several stages of switches to connect two groups of nodes and interestingly, can support multicast in an efficient manner. Our evaluation results show that CuPAN can manage the multicast-based traffic of neural networks better than the mesh-based topologies used in many parallel neural network implementations and gives lower average message latency, which directly translates to faster neural processing.

40414243444546 2101 - 2150 av 2282
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf