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  • 1851.
    Yang, Xi
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    The Use of One-Time Password and RADIUS Authentication in a GSS-API Architecture2006Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Generic Security Service Application Program Interface (GSS-API) is an architecture that facilitates applications using distributed security services in a mechanism-independent fashion. GSS-API is supported by various underlying mechanisms and technologies such as Kerberos version 5 and public-key technologies. However, no one-time password based GSS-API mechanism existed.

    This thesis focuses on an investigation using one-time passwords together with RADIUS authentication as a protection facility for a GSS-API mechanism. This thesis presents a security architecture using one-time passwords to establish a GSS-API security context between two communicating peers.

    The proposed one-time password based GSS-API mechanism could be used to enhance the security of user authentication. Moreover, the mechanism can greatly facilitate static-password based system’s transition to stronger authentication.

  • 1852.
    Yang, Yanpeng
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    A study on the deployment and cooperative operation of ultra-dense networks2017Licentiate thesis, comprehensive summary (Other academic)
    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.

  • 1853.
    Yang, Yanpeng
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Park, J.
    Sung, Ki Won
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    On the asymptotic behavior of ultra-densification under a bounded dual-slope path loss model2017In: European Wireless 2017 - 23rd European Wireless Conference, Institute of Electrical and Electronics Engineers (IEEE), 2017, 8011320Conference paper (Refereed)
    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.

  • 1854.
    Yang, Yanpeng
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Park, Jihong
    Sung, Ki Won
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    On the Asymptotic Behavior of Ultra-Densificationunder a Bounded Dual-Slope Path Loss ModelManuscript (preprint) (Other academic)
    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.

  • 1855.
    Yang, Yanpeng
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Shi, Lei
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    On the Capacity of Wi-Fi System in TV White Space with Aggregate Interference Constraint2013In: Proceedings of the 2013 8th International Conference on Cognitive Radio Oriented Wireless Networks and Communications, CROWNCOM 2013, IEEE conference proceedings, 2013, 123-128 p.Conference paper (Refereed)
    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.

  • 1856.
    Yang, Yanpeng
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Sung, Ki Won
    KTH, School of Information and Communication Technology (ICT), Communication Systems, 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 ModelManuscript (preprint) (Other academic)
    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.

  • 1857.
    Yang, Zhe
    et al.
    Dept. of Signal Processing Processing, Blekinge Institute of Technology.
    Khamit, Saltanat
    KTH, School of Information and Communication Technology (ICT), Communication Systems, 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 Sweden2008In: 3rd IEEE/IFIP International Workshop on Business-driven IT Management, 2008. BDIM 2008, IEEE conference proceedings, 2008, 116-117 p.Conference paper (Refereed)
    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.

  • 1858.
    Yanggratoke, Rerngvit
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Data-driven Performance Prediction and Resource Allocation for Cloud Services2016Doctoral thesis, comprehensive summary (Other academic)
    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.

  • 1859.
    Yanggratoke, Rerngvit
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    GPU Network Processing2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Networking technology is connecting more and more people around the world. It has become an essential part of our daily life. For this connectivity to be seamless, networks need to be fast. Nonetheless, rapid growth in network traffic and variety of communication protocols overwhelms the Central Processing Units (CPUs) processing packets in the networks. Existing solutions to this problem such as ASIC, FPGA, NPU, and TOE are not cost effective and easy to manage because they require special hardware and custom configurations.

    This thesis approaches the problem differently by offloading the network processing to off-the-shelf Graphic Processing Units (GPUs). The thesis's primary goal is to find out how the GPUs should be used for the offloading. The thesis follows the case study approach and the selected case studies are layer 2 Bloom filter forwarding and flow lookup in Openflow switch. Implementation alternatives and evaluation methodology are proposed for both of the case studies. Then, the prototype implementation for comparing between traditional CPU-only and GPU-offloading approach is developed and evaluated.

    The primary findings from this work are criteria of network processing functions suitable for GPU offloading and tradeoffs involved. The criteria are no inter-packet dependency, similar processing flows for all packets, and within-packet parallel processing opportunity. This offloading trades higher latency and memory consumption for higher throughput.

  • 1860.
    Yanggratoke, Rerngvit
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ahmed, Jawwad
    Ardelius, John
    Flinta, Christofer
    Johnsson, Andreas
    Gillblad, Daniel
    Swedish Institute of Computer Science (SICS), Sweden.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Predicting Real-time Service-level Metrics from Device Statistics2014Report (Other academic)
    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.

  • 1861.
    Yanggratoke, Rerngvit
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, 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, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Predicting Real-time Service-level Metrics from Device Statistics2015In: IFIP/IEEE International Symposium on Integrated Network Management, IM 2015, Ottawa, Canada, IEEE Communications Society, 2015Conference paper (Refereed)
    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.

  • 1862.
    Yanggratoke, Rerngvit
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Networks.
    Ahmed, Jawwad
    Ardelius, John
    Flinta, Christofer
    Johnsson, Andreas
    Gillblad, Daniel
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Predicting service metrics for cluster-based services using real-time analytics2015In: IFIP/IEEE 11th International Conference on Network and Service Management, CNSM 2015, Barcelona, Spain, November 9-13, 2015, IEEE conference proceedings, 2015Conference paper (Refereed)
    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.

  • 1863.
    Yanggratoke, Rerngvit
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Networks.
    Ahmed, Jawwad
    Ardelius, John
    Flinta, Christoffer
    Johnsson, Andreas
    Gillblad, Daniel
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A service-agnostic method for predicting service metrics in real-timeManuscript (preprint) (Other academic)
    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.

  • 1864.
    Yanggratoke, Rerngvit
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Azfar, Abdullah
    Marval, María José Peroza
    Ahmed, Sharjeel
    Delay Tolerant Network on Android Phones: Implementation Issues and Performance Measurements2011In: Journal of Communications, ISSN 1796-2021, E-ISSN 1796-2021, Vol. 6, no 6, 477-484 p.Article in journal (Refereed)
    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.

  • 1865.
    Yanggratoke, Rerngvit
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Networks.
    El Hosary, Amira
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Networks.
    Selected Paper on Network and Cloud Analytics2016Report (Other academic)
    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.

  • 1866.
    Yanggratoke, Rerngvit
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kreitz, Gunnar
    Spotify.
    Goldmann, Mikael
    Spotify.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Networks.
    Predicting response times for the Spotify backend2012Report (Other academic)
    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.

  • 1867.
    Yanggratoke, Rerngvit
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kreitz, Gunnar
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS. Spotify AB.
    Goldmann, Mikael
    Spotify AB.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fodor, Viktoria
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Networks.
    On the performance of the Spotify backend2013In: Journal of Network and Systems Management, ISSN 1064-7570, E-ISSN 1573-7705Article in journal (Refereed)
    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.

  • 1868. Yasoubi, A.
    et al.
    Hojabr, R.
    Takshi, H.
    Modarressi, M.
    Daneshtalab, Masoud
    KTH, School of Information and Communication Technology (ICT), Electronics and Embedded Systems.
    CuPAN - high throughput on-chip interconnection for neural networks2015In: 22nd International Conference on Neural Information Processing, ICONIP 2015, Springer, 2015, 559-566 p.Conference paper (Refereed)
    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.

  • 1869.
    Yavari, Ali
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Measuring the Quality of Experience of Mobile Video StreamingManuscript (preprint) (Other academic)
    Abstract [en]

    In recent years the growing popularity of mobile phones with the ability of accessing the Internet has increased the usage of video streaming services on the mobile phone devices. These devices can access the Internet using different technologies like Wi-Fi, Bluetooth or Wide Area cellular accesses like GPRS, 3G or 4G. Video streaming services typically consume more data than other successful services like e-mails, photo sharing and web-browsing, and their performances are limited by the bandwidth and data rates that can be provided by current mobile networks. Resource limitations in mobile networks are typically translated into data starvation and interruptions in the video streaming playbacks, leading to low user satisfaction levels. In order to evaluate the users’ satisfaction of the mobile video streaming services, in current heterogeneous mobile networks, it is necessary to introduce techniques to measure the users’ video streaming quality of experience which relates to how users perceive the quality of video streaming playback. In this paper we present an overview of various techniques for measuring the users’ QoE of mobile video streaming service.

  • 1870.
    Yavari, Ali
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Lungaro, Pietro
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Segall, Zary
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Network Efficient Resource Management for Mobile Video Streaming based on Quality of Experience2013In: 2013 International Conference on ICT Convergence (ICTC): , IEEE Communications Society, 2013, 654-659 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a novel experimental approach to quantify the performances of Quality of Experience (QoE)- aware resource management scheme in mobile network. The main goal of this paper is to improve network efficiency by exploiting knowledge of QoE information associated with online video streaming services. The investigations considered in the paper are performed using an innovative test-bed, developed to assess network efficiency for the provision of online video services of different qualities. The QoE model used in the proposed QoEaware allocation scheme assumes a MOS-like grading function whose grades depend on both the duration of playtime interruption and the streaming video quality (resolution). The results show that the proposed resource management scheme can deliver more than 40 percent higher QoE to the users of the system as compared to current agnostic (not aware of QoE requirement and content characteristics) service models.

  • 1871.
    Yavari, Ali
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Lungaro, Pietro
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Segall, Zary
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Towards a Semantic-aware Location Positioning for Smart-phones2013In: 2013 Fifth International Conference on Ubiquitous and Future Networks (ICUFN), IEEE conference proceedings, 2013, 487-488 p.Conference paper (Refereed)
    Abstract [en]

    Location-aware services and applications have be- come quite popular in the daily life of mobile users. Global Positioning System (GPS) is available in almost all new smart- phones as a mature and accurate positioning technique. GPS as a satellite-based navigation system, determines the current location of users by receiving signals from satellites. Satellite signals cannot propagate properly inside the buildings, which makes it unusable for indoor positioning. In addition, GPS consumes too much energy to be useful for many applications on mobile phones. There are many proposed alternatives for GPS but they are not as accurate. Combination of those alternatives can improve the accuracy, but varies widely depending on the user behavior and environment. This paper presents a novel architecture for semantic-aware positioning that chooses the best positioning method(s) by exploiting the semantic knowledge. 

  • 1872.
    Yavari, Ali
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Martinez Ballesteros, Luis Guillermo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Lungaro, Pietro
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Segall, Zary
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    Quality of Experience-aware Resource Management for Mobile Video StreamingManuscript (preprint) (Other academic)
    Abstract [en]

    In this paper, we present a novel experimental approach to quantify the performances of Quality of Experience (QoE)-aware resource management scheme in mobile networks. The main goal of this paper is to improve network efficiency by exploiting in the resource management the knowledge of QoE information associated with online video streaming services. The investigations considered in the paper are performed using an innovative test-bed, developed to assess network efficiency, as well as the impact on the energy consumption at mobile terminal (MT), for the provision of online video services of different qualities. The QoE model used in the proposed QoE-aware allocation scheme assumes a MOS-like grading function whose grades depend on both the duration of playtime interruption and the video quality (resolution). The results show that the proposed resource management scheme can deliver more than 40 percent higher QoE and energy saving at mobile terminal between 12% to 15% to the users of the system as compared to current agnostic (not aware of QoE requirement and content characteristics) service models.

  • 1873.
    Yaver, Ali
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Communication Systems, CoS (closed 2012-01-01).
    Koudouridis, G. P.
    Utilization of multi-radio access networks for video streaming services2009In: 2009 IEEE Wireless Communications & Networking Conference (WCNC ), 2009, 4918018- p.Conference paper (Refereed)
    Abstract [en]

    In comparison to traditional voice based circuit switched mobile systems, the multimedia content puts forward significantly strict quality of service requirements. In this perspective, a noticeable proportion of contemporary research has been driven towards exploring the possibilities of simultaneously utilizing geographically co-existing mobile networks belonging to a wide range of wireless technologies. This paper evaluates such co-existence by means of a novel macro diversity scheme referred to as Multi Radio Transmission Diversity (MRTD) which exploits the dynamic cooperation between the networks at the radio link level. Relevant QoS parameters for an MPEG4 encoded video streaming service have been analyzed by means of simulations in a hybrid network topology consisting of IEEE 802.11b WLAN and UMTS HSDPA. The performance gains have been observed for various load and radio propagation conditions in comparison to a benchmark system which is not capable of utilizing such cooperation between multiple network interfaces.

  • 1874.
    Yavuz, Emre A.
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Poster: Collective Mobile Sensing for Wireless Network Performance Monitoring2011In: Proc. ACM Annual International Conference on Mobile Systems, Applications and Services, 2011, 411- p.Conference paper (Refereed)
    Abstract [en]

    Rapid growth of mobile wireless industry has generated numerous challenges for service operators. The provisioning of increasing demand in capacity and higher quality of service can be met with redimensioning of networks which makes a priori network planning difficult. We propose a network performance monitoring system to which all mobile devices contribute by voluntarily submitting periodical reports on the availability and quality of network access that they experience at their current geographical locations. Network performance measures such as signal strength, coverage, call block/drop statistics and operator service capabilities are reported to a server with a network status information database as experienced by mobile devices. The proposed database will indicate areas with lack of coverage, insufficient capacity, and high interference, which may serve as cues for operators to upgrade/retune their infrastructure equipment and for regulators to take action against operators that do not fulfill commitments made to their subscribers.

  • 1875.
    Yavuz, Emre A.
    et al.
    Dept. of Electrical & Computer Engineering - University of British Columbia (UBC).
    Leung, Victor C. M.
    A practical method for estimating performance metrics of call admission control schemes in wireless mobile networks2005In: 2005 IEEE Wireless Communications and Networking Conference, Vols 1-4: WCNC 2005: BROADBAND WIRELESS FOR THE MASSES READY FOR TAKE-OFF, 2005, Vol. 2, 1254-1259 p.Conference paper (Refereed)
    Abstract [en]

    Providing the desired call blocking probability to not only new but also existing calls has been a challenge for wireless mobile network service providers. To satisfy different requirements for new and handoff call blocking probabilities, several call admission control (CAC) schemes have been proposed in the literature. Exact analysis of these schemes using two dimensional Markov chain is computationally intensive. Therefore under specific assumptions computationally efficient methods to analyze these systems using one dimensional Markov chain models have been considered. The "traditional" approach assumes that channel holding time for new and handoff calls have equal mean values. While the "normalized" approach relaxes this assumption, it is accurate only for the new call bounding CAC scheme. In this paper, we reevaluate the analytical methods for computing call blocking probabilities for several widely known call admission control schemes under more general assumptions by providing an easy to implement method. The numerical results show that when the average values of channel holding times for new and handoff calls are different, the proposed approach gives more accurate results when compared with the traditional and normalized methods based on one dimensional Markov chain modeling, while keeping the computational complexity low.

  • 1876.
    Yavuz, Emre A.
    et al.
    Dept. of Electrical & Computer Engineering - University of British Columbia (UBC).
    Leung, Victor C. M.
    Computationally efficient method to evaluate the performance of guard-channel-based call admission control in cellular networks2006In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 55, no 4, 1412-1424 p.Article in journal (Refereed)
    Abstract [en]

    Many guard-channel-based call admission control (CAC) schemes for cellular networks have been proposed to provide the desired quality of service to not only new calls but also ongoing calls when they hand off to neighboring cells. Blocking/dropping probabilities of new/handoff calls are generally analyzed using one-dimensional Markov chain modeling under specific assumptions to avoid solving large sets of flow equations that makes exact analyses of these schemes using multidimensional Markov chain models infeasible. This is the case with the "traditional" approach, which assumes that channel holding times for new and handoff calls have equal mean values, and the "normalized" approach, which relaxes this assumption but is accurate only for the new call bounding CAC scheme. In this paper, we reevaluate the analytical methods for computing new/handoff call blocking/dropping probabilities for several widely known CAC schemes and develop an easy-to-implement method under more general assumptions. Numerical results show that when the mean channel holding times for new and handoff calls are different, the proposed "effective holding time" approach gives more accurate results compared with the traditional and the normalized methods while keeping the computational complexity low. The accuracy of these methods and their levels of computational complexity with the exact solution are also compared.

  • 1877.
    Yavuz, Emre A.
    et al.
    Dept. of Electrical & Computer Engineering - University of British Columbia (UBC).
    Leung, Victor C. M.
    Efficient approximations for call admission control performance evaluations in multi-service networks2006In: GLOBECOM 2006: 2006 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, 2006, Vol. WLC40-5Conference paper (Refereed)
    Abstract [en]

    Several dynamic call admission control (CAC) schemes for cellular networks have been proposed in the literature to reserve resources adaptively to provide the desired quality of service (QoS) to not only high priority calls but also to low priority ones. Efficient adaptive reservations depend on reliable and up-to-date system status feedback provided to the CAC mechanism. However exact analysis of these schemes using multidimensional Markov chain models are intractable in real time due to the need to solve large sets of flow equations. Hence performance metrics such as call blocking probabilities of various QoS classes are generally evaluated using one dimensional Markov chain models assuming that channel occupancy times for all QoS classes have equal mean values and all arriving calls have equal capacity requirements. In this paper we re-evaluate the analytical methods to compute call blocking probabilities of various QoS classes for several widely known CAC schemes by relaxing these assumptions, and propose a novel approximation method for performance evaluation with low computational complexity. Numerical results show that proposed method provides results that match well with the exact solutions.

  • 1878.
    Yavuz, Emre A.
    et al.
    Dept. of Electrical & Computer Engineering - University of British Columbia (UBC).
    Leung, Victor C. M.
    Efficient Methods for Performance Evaluations of Call Admission Control Schemes in Multi-Service Cellular Networks2008In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 7, no 9, 3468-3476 p.Article in journal (Refereed)
    Abstract [en]

    Many dynamic call admission control (CAC) schemes have been proposed in the literature for adaptive reservations in cellular networks. Efficient application of these schemes requires reliable and up-to-date feedback of system performance to the CAC mechanism. However, exact analyses of these schemes in real time using multi-dimensional Markov chain models are challenging due to the need to solve large sets of flow equations. One dimensional Markov chain models have been widely used to derive performance metrics such as call blocking probabilities of multiple traffic classes assuming that all classes of calls have equal capacity requirements and exponentially distributed channel holding times with equal mean values. These assumptions need to be relaxed for a more general evaluation of CAC performance in multi-service cellular networks. In this paper we classify CAC schemes according to their Markov chain models into two categories: symmetric and asymmetric, and develop computationally efficient analytical methods to compute call blocking probabilities of various traffic classes for several widely known CAC schemes under relaxed assumptions. We obtain a product form solution to evaluate symmetric schemes and propose a novel performance evaluation approximation method with low computational cost for asymmetric schemes. Numerical results demonstrate the accuracy and efficiency of the proposed method.

  • 1879.
    Yavuz, Emre A.
    et al.
    Dept. of Electrical & Computer Engineering - University of British Columbia (UBC).
    Leung, Victor C. M.
    Modelling channel occupancy times for voice traffic in cellular networks2007In: 2007 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, VOLS 1-14, 2007, 332-337 p.Conference paper (Refereed)
    Abstract [en]

    Call holding times in telephony networks are commonly approximated by exponential distributions to facilitate traffic engineering. However, for traffic engineering of cellular networks, channel occupancy times need to be modeled instead to facilitate analytical modeling or to feed network simulations. In this paper, we classify channel occupancy times and present an empirical study based on data obtained from a real cellular network to determine which probability distribution functions can approximate them better. The results are environment dependent, but no assumptions that can be influential are made, as opposed to previous analytical and simulation studies which results are highly dependent on the assumptions made by the authors. We show that all types of channel occupancy times can be approximated by lognormal distribution. For stationary users, channel occupancy times are commonly approximated by exponential distribution due to its tractability, assuming that cell residence times are also exponentially distributed. However, we show that lognormal distribution fits much better to both channel occupancy and call holding times regardless of whether users are stationary or mobile.

  • 1880.
    Ye, Lin
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fodor, Viktoria
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Giannetsos, Athanasios
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Papadimitratos, Panagiotis
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Path metric authentication for low-power and lossy networks2015In: 1st ACM International Workshop on Cyber-Physical Systems for Smart Water Networks, CySWater 2015, Association for Computing Machinery (ACM), 2015Conference paper (Refereed)
    Abstract [en]

    Cyber physical systems often require sensor networks to perform unattended operation for a long time, while providing performance guarantees for monitoring and control applications. Since this poses requirements on the formed wireless sensor network topology, routing protocols provide a means to construct topologies according to complex objective functions, involving several routing metrics. As the metric values affect the emerging topology significantly, they need to be protected, to avoid topology formation attacks from malicious users. In this paper we consider the specific case of RPL based routing and propose a lightweight authentication approach to protect RPL path metrics. We evaluate the cost of metric authentication and show how to tradeoff the introduced tree construction delay and the achieved metric accuracy.

  • 1881.
    Ye, Yu
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Zhang, Z.
    Yang, Guang
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Minimum cost based clustering scheme for cooperative wireless caching network with heterogeneous file preference2017In: 2017 IEEE International Conference on Communications (ICC) 2017 IEEE International Conference on Communications (ICC) took place 21-25 May 2017 in Paris, France, Institute of Electrical and Electronics Engineers (IEEE), 2017, 7997449Conference paper (Refereed)
    Abstract [en]

    Wireless caching enables popular files to be stored at the base stations (BSs) in advance, which has been considered as an efficient way to reduce the service delay and alleviate heavy burdens on the backhaul links. In this paper, we study the BS clustering scheme for the cooperative wireless caching networks (CWCNs) with heterogeneous file preference among users and BSs, and propose the minimum cost (MC) based clustering scheme. We first introduce the weight-based cost function, which characterizes the trade-off between service delay and transmission cost, and then formulate the clustering as the optimization problem. Furthermore, two clustering algorithms are developed to solve the optimization problem. The results show that the proposed scheme can achieve lower cost compared with random clustering scheme.

  • 1882. Yetis, Cenk M.
    et al.
    Fanjul, Jacobo
    Garcia-Naya, Jose A.
    Moghadam, Nima N.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Farhadi, Hamed
    Interference Alignment Testbeds2017In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 55, no 10, 120-126 p.Article in journal (Refereed)
    Abstract [en]

    Interference alignment has triggered high impact research in wireless communications since it was proposed nearly 10 years ago. However, the vast majority of research is centered on the theory of interference alignment and is hardly feasible in view of the existing state-of-the-art wireless technologies. Although several research groups have assessed the feasibility of interference alignment via testbed measurements in realistic environments, the experimental evaluation of interference alignment is still in its infancy since most of the experiments were limited to simpler scenarios and configurations. This article summarizes the practical limitations of experimentally evaluating interference alignment, provides an overview of the available interference alignment testbed implementations, including the costs, and highlights the imperatives for succeeding interference alignment testbed implementations. Finally, the article explores future research directions on the applications of interference alignment in the next generation wireless systems.

  • 1883.
    Yi, Xiaokun
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Adaptive Wireless Multimedia Services2006Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Context-awareness is a hot topic in mobile computing currently. A lot of importance is being attached to facilitating the user of various mobile computing devices to provide services that are more “user-centric”. One aspect of context-awareness is to perceive variations in available resources, and to make decisions based on the feedback to enable applications to automatically adapt to the current environment.

    For Voice over IP (VoIP) software phones (softphones), variations in network performance lead to fluctuations in the quality of the communication. Therefore, by making these softphones more adaptive to the network environment will, to some extent, mask such fluctuations. Dynamic voice and video adaptation derives from the fact that different coder-decoders (CODEC) have different characteristics, even the same CODECs with a different configuration can behave quite differently, in terms of bandwidth consumption, packet size, etc.

    Minisip is a VoIP client application which was implemented on and targeted for a Linux platform. One of my tasks was to port Minisip to Microsoft’s Windows Mobile operating system, running on an HP IPAQ Pocket PC H5550. Such handheld computer enables the user to communication while they are moving about, thus increasing the probability that the characteristics of the network connection will change. Building upon this port, the next task was to add dynamic voice and video CODEC adaptation. Dynamic voice and video CODEC adaptation on Minisip poses several challenges, for example, in what way can the network performance be determined and what adaptation strategy can achieve high call quality while making efficient utilization of available network resources.

    In order to make the proper design choices, several estimation models will be discussed, these are used to determine an efficient, un-intrusive, and light weight means of dynamic CODEC selection within Minisip. This thesis only implemented audio CODEC adaptation of Minisip, and the evaluation of the resulting prototype shows that such dynamic adaptation is both feasible and practical; further more, video CODEC adaptation would be a more significant extension to this work in the future.

  • 1884. Yin, X.
    et al.
    Verplaetse, M.
    Lin, Rui
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Van Kerrebrouck, J.
    Ozolins, O.
    De Keulenaer, T.
    Pang, X.
    Pierco, R.
    Vyncke, A.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Fotonik och mikrovågsteknik, FMI.
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Fotonik och mikrovågsteknik, FMI.
    Jacobsen, Gunnar
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Fotonik och mikrovågsteknik, FMI. Acreo.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Torfs, G.
    Bauwelinck, J.
    First Demonstration of Real-Time 100 Gbit/s 3-level Duobinary Transmission for Optical Interconnects2016Conference paper (Refereed)
  • 1885. Yin, Xin
    et al.
    Verplaetse, Michiel
    Lin, Rui
    Van Kerrebrouck, Joris
    Ozolins, Oskars
    De Keulenaer, Timothy
    Pang, Xiaodan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). RISE ACREO AB.
    Pierco, Ramses
    Vaernewyck, Renato
    Vyncke, Arno
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics, Fotonik och mikrovågsteknik.
    Westergren, Urban
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Torfs, Guy
    Bauwelinck, Johan
    First demonstration of real-time 100 Gbit/s 3-Level duobinary transmission for optical interconnects2016In: ECOC 2016-Post Deadline Paper; 42nd European Conference on Optical Communication; Proceedings of, 2016, 1-3 p.Conference paper (Refereed)
  • 1886. Ying, Z.
    et al.
    Chiu, C. -Y
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Sony Mobile Communications AB, Sweden.
    Zhang, S.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Antenna design for diversity and MIMO application2016In: Handbook of Antenna Technologies, Springer, 2016, Vol. 2, 1479-1530 p.Chapter in book (Refereed)
    Abstract [en]

    Recently, multiple-input multiple-output (MIMO) technology and diversity have attracted much attention both in industry and academia due to high data rate and high spectrum efficiency. By increasing the number of antennas at the transmitter and/or the receiver side of the wireless link, the diversity/MIMO techniques can increase wireless channel capacity without the need of additional power or spectrum in rich scattering environments. However, due to limited space of small mobile devices, the correlation coefficients between MIMO antenna elements are usually very high, and the total efficiencies of MIMO elements would be degraded severely due to mutual couplings. In addition, the human body causes high losses on electromagnetic waves. In real applications, the presence of users may result in significant reduction of total antenna efficiencies, and the correlations of MIMO antenna systems are also highly affected. In this chapter, the performance of some basic MIMO antennas as well as recent technologies to improve MIMO antenna performance of portable devices and mobile terminals are reviewed. The interactions between MIMO antennas and human body are also addressed particularly in mobile terminals application.

  • 1887. Yoo, S. J. B.
    et al.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    InP photonic integrated circuits for optical communciations2008Conference paper (Refereed)
    Abstract [en]

    This paper describes photonic integration circuits (PICs) realized on the InP platform including high-speed mode locked lasers, arrayed waveguide gratings (AWGs), differential Mach-Zehnder optical switches (MZI), and high-speed amplitude and phase modulators. Selected area hydride vapor phase epitaxy (HVPE) and organometallic chemical vapor deposition (OMCVD) were used to realized planarized and passivated integration including active and passive elements. The integrated chips of various configurations were investigated for 'Optical Code Division Multiple Access (O-CDMA)', in local area networks, and for 'Optical Arbitrary Waveform Generation (OAWG),' in high-speed otptical communications.

  • 1888. Yu, Xianbin
    et al.
    Jia, Shi
    Pang, Xiaodan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). RISE ACREO AB.
    Morioka, Toshio
    Oxenloewe, Leif K.
    Beyond 100 Gbit/s wireless connectivity enabled by THz photonics2017In: Transparent Optical Networks (ICTON), 2017 19th International Conference on, IEEE Computer Society, 2017, 1-4 p.Conference paper (Refereed)
    Abstract [en]

    Beyond 100Gbit/s wireless connectivity is appreciated in many scenarios, such as big data wireless cloud, ultrafast wireless download, large volume data transfer, etc. In this paper, we will present our recent achievements on beyond 100Gbit/s ultrafast terahertz (THz) wireless links enabled by THz photonics.

  • 1889. Yu, Xianbin
    et al.
    Zhao, Ying
    Deng, Lei
    Pang, Xiaodan
    RISE ACREO AB; Technical University of Denmark.
    Tafur Monroy, Idelfonso
    Existing PON Infrastructure Supported Hybrid Fiber-Wireless Sensor Networks2012In: National Fiber Optic Engineers Conference, NFOEC 2012, 2012Conference paper (Refereed)
    Abstract [en]

    We propose a hybrid fiber wireless sensor network based on the existing PON infrastructure. The feasibility of remote sensing and PON convergence is experimentally proven by transmitting direct-sequence spread-spectrum wireless sensing and 2.5Gbps GPON signals.

  • 1890.
    Yuan, Xiaolong
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Wu, X.
    Signell, S.
    Continuous-time quadrature bandpass sigma delta modulators with different feedback DAC2008In: IEEE Int. Conf. Circuits Syst. Commun., ICCSC, 2008, 580-583 p.Conference paper (Refereed)
    Abstract [en]

    Continuous time (CT) quadrature bandpass sigma delta modulators (QBSDM) are widely used in wireless receivers recently due to its inherent anti-aliasing filtering and complex filtering embedded in the loops to efficiently realize asymmetric noise-shaping. The complex noise-transfer-function (NTF) can be realized with complex coefficients or by implementing the loop as a cascade of complex integrators with only real coefficients, which is desirable due to its lower sensitivity to loop mismatch. In this paper, we will study the effect of different feedback waveforms inside the modulator on the NTF of quadrature sigma delta modulators. Complex NTF design is discussed for different bandpass center frequencies relative to the sampling frequency.

  • 1891.
    Yuan, Zhao
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Implementing zonal pricing in distribution network: The concept of pricing equivalence2016In: IEEE Power and Energy Society General Meeting, IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    Distribution locational marginal pricing (DLMP) is critical market mechanism to boost services from distributed energy resources (DER). This paper propose to design zonal pricing in distribution network according to the concept of pricing equivalence (PE). The rules of the zonal pricing are derived. We prove that equivalent load shift from demand response can be achieved by zonal pricing if pricing equivalence is deployed. Convex AC optimal power flow (OPF) is used to calculate zonal prices. The benefits of convex AC OPF are more accurate energy pricing and global optimization target. The responsive load with passive load controllers are modeled and solved in GAMS platform. Different zonal pricing approaches (PE, reference node and average of nodal prices) are compared. IEEE 14-bus network and two IEEE 13-node networks are connected to be an illustrative test case offering numerical results. The results show that zonal pricing designed according to PE can achieve the same load shift effects and quite close consumer payments as nodal pricing. PE outperform other zonal pricing approaches prominently in congested network situations.

  • 1892. Yun, S. -Y
    et al.
    Proutiere, Alexandre
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Distributed proportional fair load balancing in heterogenous systems2015In: Performance Evaluation Review, ACM Press, 2015, Vol. 43, no 1, 17-30 p.Conference paper (Refereed)
    Abstract [en]

    We consider the problem of distributed load balancing in heterogenous parallel server systems, where the service rate achieved by a user at a server depends on both the user and the server. Such heterogeneity typically arises in wireless networks (e.g., servers may represent frequency bands, and the service rate of a user varies across bands). We assume that each server equally shares in time its capacity among users allocated to it. Users initially attach to an arbitrary server, but at random instants of time, they probe the load at a new server and migrate there if this improves their service rate. The dynamics under this distributed load balancing scheme, referred to as Random Local Search (RLS), may be interpreted as those generated by strategic players updating their strategy in a load balancing game. In closed systems, where the user population is fixed, we show that this game has pure Nash Equilibriums (NEs), and that these equilibriums get close to a Proportionally Fair (PF) allocation of users to servers when the user population grows large. We provide an anytime upper bound of the gap between the allocation under RLS and the PF allocation. In open systems, where users randomly enter the system and leave upon service completion, we establish that the RLS algorithm stabilizes the system whenever this it at all possible under centralized load balancing schemes, i.e., it is throughput-optimal. The proof of this result relies on a novel Lyapounov analysis that captures the dynamics due to both users’ migration and their arrivals and departures. To our knowledge, the RLS algorithm constitutes the first fully distributed and throughputoptimal load balancing scheme in heterogenous parallel server systems. We extend our analysis to various scenarios, e.g. to cases where users can be simultaneously served by several servers. Finally we illustrate through numerical experiments the efficiency of the RLS algorithm.

  • 1893.
    Yunda Lozano, Daniel
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Improving vertical handover performance for RTP streams containing voice: Using network parameters to predict future network conditions in order to make a vertical handover decision2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wireless local area networks WLAN and Voice over IP technologies enable local low cost wireless telephony, while cellular networks offer wide-area coverage. The use of dual mode WLAN-cellular terminals should allow cost savings by automatically switching from GSM to WLAN networks whenever it is feasible. However, in order to allow user mobility during a call, a handover procedure for transferring a call between the WLAN interface and the cellular network should be defined. The decision algorithm that triggers such a handover is critical to maintain voice quality and uninterrupted communication. Information or measurements collected from the network may be used to anticipate when the connection will degrade to such a point that a handover is desirable in order to allow a sufficient time span for the handover’s successful execution. It is the delay in detecting when to make a handover and the time to execute it that motivates the need for a prediction.

    The goal of this thesis is therefore to present a method to predict when a handover should be made based upon network conditions. We selected a number of WLAN and VoIP software tools and adapted them to perform the measurements. These tools allowed us to measure parameters of the WLAN’s physical and link layers. Packet losses and jitter measurements were used as well. We have assumed that there is ubiquitous cellular coverage so that we only have to be concerned with upward handovers (i.e, from the WLAN to the cellular network and not the reverse). Finally we have designed and evaluated a mechanism that triggers the handover based in these measurements.

  • 1894. Zafar, B.
    et al.
    Ben Slimane, Slimane
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Communication Systems, CoS (closed 2012-01-01).
    Javed, Muhammad Umar
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Communication Systems, CoS (closed 2012-01-01).
    Network product coding2010In: 2010 7th IEEE Consumer Communications and Networking Conference, CCNC 2010, IEEE , 2010, -266 p.Conference paper (Refereed)
    Abstract [en]

    Network coding is a useful tool to increase the multicast capacity of networks. The traditional approach to network coding involving XOR operation has several limitations such as low robustness and can support only two users/packets at a time,per relay, in the mixing process to achieve optimal error performance. We propose the employment of product coding at the relay station instead of xor and investigate such a system where we use the relay to generate product codes by combining packets from different users. Our scheme uses relays to transmit only the redundancy of the product code instead of the whole product code. We seek to employ product coding can be able to support more than two users/packets per relay per slot, while maintaining a good error performance. Our scheme can accomodate as many users per relay as the costituent block code allows, thus reducing the number of relays required in the network.Product codes also offer increased robustness and flexibility as well as several other advantages, such as proper structure for burst error correction without extra interleaving. We compare the performance of such a scheme to the conventional xor scheme and see that our scheme not only reduces the number of relays required but gives improved error performance as well as. Another encouraging result is that our scheme starts to significantly outperform the conventional one by introducing a gain at the relay.

  • 1895.
    Zafar, Bilal
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Network Coding Employing Product Coding at Relay Stations2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Network coding is a useful tool to increase the multicast capacity of networks. The traditional approach to network coding involving XOR operation has several limitations such as low robustness and can support only two users/packets at a time,per relay, in the mixing process to achieve optimal error performance. We propose the employment of product coding at the relay station instead of xor and investigate such a system where we use the relay to generate product codes by combining packets from different users.Our scheme uses relays to transmit only the redundancy of the product code instead of the whole product code.We seek to employ product coding can be able to support more than two users/packets per relay per slot,while maintaining a good error performance. Our scheme can accomodate as many users per relay as the costituent block code allows, thus reducing the number of relays required in the network. Product codes also offer increased robustness and flexibility as well as several other advantages, such as proper structure for burst error correction without extra interleaving. We compare the performance of such a scheme to the conventional xor scheme and see that our scheme not only reduces the number of relays required but gives improved error performance as well as. Another encouraging result is that our scheme starts to significantly outperform the conventional one by introducing a gain at the relay.

  • 1896. Zaidi, A. A.
    et al.
    Oechtering, Tobias J.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Stabilization of noisy plants over a Gaussian interference channel2014In: IWCIT 2014 - Iran Workshop on Communication and Information Theory, 2014Conference paper (Refereed)
    Abstract [en]

    Remote stabilization of two noisy linear plants over a symmetric Gaussian interference channel with possibly noisy feedback from controllers to the plants is studied. Each plant is monitored by a separate sensor which communicates its observations to a separate controller over a Gaussian interference channel. The controllers aim at stabilizing the two plants in mean-square sense. The plant noise is assumed to be additive white Gaussian distributed. A delay-free sensing and control scheme is proposed, which is an adaptation of the Schalkwijk-Kailath type coding schemes developed for transmission of reliable information over channels with noiseless feedback. The conditions that guarantee the stabilization of the noisy plants under the proposed scheme are derived, extending the results that are known for mean-square stabilization of noiseless plants over noiseless feedback channels. Numerical results indicate that the stabilizability is not affected by the inclusion of an additive Gaussian noise in the plant models under the proposed scheme.

  • 1897.
    Zaki, Ahmed
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Wang, Chao
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Combining interference alignment and Alamouti codes for the 3-user MIMO interference channel2013In: 2013 IEEE Wireless Communications and Networking Conference (WCNC), New York: IEEE , 2013, 3563-3567 p.Conference paper (Refereed)
    Abstract [en]

    The interference channel (IC) is the basic underlying channel model for many practical multi-terminal communication scenarios. Here, we consider a modified three-user IC with dual-antenna transmitters and receivers where we allow one receiver to have a finite-rate unidirectional link to another receiver. This kind of receiver-to-receiver link may exist in cellular networks with base-station backhaul. For this scenario we propose a scheme that combines the interference-cancellation capability of Alamouti codes with the subspace-overlapping property of interference alignment to achieve a sum-rate of three symbols/channel use. The scheme does also simultaneously provide a diversity gain of two for every symbol which significantly improves the bit-error rate performance compared to zero-forcing techniques.

  • 1898.
    Zamaere, Bruce
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Hidell, Markus
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Sjödin, Peter
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    CVPN: A multi-homed VPN solution for remote patient monitoring2012In: 2012 IEEE 14th International Conference on e-Health Networking, Applications and Services, Healthcom 2012, IEEE , 2012, 279-285 p.Conference paper (Refereed)
    Abstract [en]

    This paper addresses the challenges of reliably, and securely, extending a healthcare provider's network into the homes of its patients in order to provide Remote Patient Monitoring (RPM) services. It describes the Carenet Virtual Private Network (CVPN) solution, a multi-homed VPN solution implemented as a virtual device driver under Linux. We describe CVPN's architecture and implementation, motivating its design decisions. The initial experimental evaluation, of our proof-of-concept prototype, shows that CVPN's per packet overhead, forwarding delay, and fail-over time are reasonable for healthcare monitoring applications and time-sensitive synchronous communications.

  • 1899.
    Zander, Jens
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Mähönen, Petri
    Riding the Data Tsunami in the Cloud: Myths and Challenges in Future Wireless Access2013In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 51, no 3, 145-151 p.Article in journal (Refereed)
    Abstract [en]

    Data rates of mobile communications have increased dramatically during the last decade. The industry predicts an exponential increase of data traffic that would correspond to a 1000-fold increase in traffic between 2010 and 2020. These figures are very similar to ones reported during the last Internet boom. In this article we assess the realism of these assumptions. We conjecture that wireless and mobile Internet access will emerge as a dominant technology. A necessary prerequisite for this development is that wireless access is abundant and becomes (almost) free. A consequence is that the projected capacity increase must be provided at the same cost and energy consumption as today. We explore technical and architectural solutions that have realistic possibility to achieve these targets. We ask if Moore's law, which has successfully predicted the tremendous advances in computing and signal processing, will also save the day for high-speed wireless access. We argue that further improvements of the PHY layer are possible, but it is unlikely that this alone provides a viable path. The exponential traffic increase has to be matched mainly by increasing the density of the access networks as well as providing a modest amount of extra spectrum. Thus, the future research challenges are in designing energy-and cost-efficient short-range architectures and systems that support super-dense deployments. A non-technical complication is that such infrastructures are likely to lead to highly fragmented markets with a large number of operators and infrastructure owners.

  • 1900.
    Zander, Jens
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sung, Ki Won
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Maehoenen, Petri
    Petrova, Marina
    Jantti, Riku
    Kronander, Jonas
    On the scalability of cognitive radio:: Assessing the commercial viability of secondary spectrum access2013In: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 20, no 2, 28-35 p.Article in journal (Refereed)
    Abstract [en]

    We report results from the recently finished QUASAR project, which has studied overall system aspects of cognitive radio technologies and has paid attention particularly to the economic viability of different use cases. We find that successful secondary sharing goes far beyond the detection of spectrum holes. Large-scale commercial success requires that secondary systems are scalable so that a large number of users can be served in an economically viable fashion. Our key finding is that secondary spectrum use is not an attractive method for most of the commercially interesting scenarios, from neither a business nor technical perspective. Perhaps somewhat surprisingly, the likely commercial "sweet spot" for secondary sharing in the lower frequency bands is short-range indoor communications. We also find that regulation does not currently present a significant barrier in Europe or the United States.

353637383940 1851 - 1900 of 1976
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