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  • 3051.
    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.

  • 3052.
    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.

  • 3053.
    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.

  • 3054.
    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.

  • 3055.
    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.

  • 3056.
    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, J.
    Kim, S. -L
    Kim, K. S.
    Cooperative transmissions in ultra-dense networks under a bounded dual-slope path loss model2017In: 2017 European Conference on Networks and Communications (EuCNC), Institute of Electrical and Electronics Engineers (IEEE), 2017Conference paper (Refereed)
    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.

  • 3057.
    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.

  • 3058.
    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.

  • 3059.
    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.

  • 3060.
    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.

  • 3061.
    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.

  • 3062.
    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.

  • 3063.
    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.

  • 3064.
    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.

  • 3065.
    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.

  • 3066.
    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.

  • 3067.
    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.

  • 3068.
    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.

  • 3069. 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.

  • 3070.
    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.

  • 3071.
    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.

  • 3072.
    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. 

  • 3073.
    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.

  • 3074.
    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.

  • 3075.
    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.

  • 3076.
    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.

  • 3077.
    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.

  • 3078.
    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.

  • 3079.
    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.

  • 3080.
    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.

  • 3081.
    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.

  • 3082.
    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.

  • 3083.
    Yedugundla, Kiran
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Hurtig, Per
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Multipath TCP: Can it Reduce Transport Latency for Web Traffic?2015Conference paper (Refereed)
  • 3084.
    Yekeh, Farahnaz
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Pordel, Mostafa
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Almeida, Luís
    University of Porto.
    Behnam, Moris
    Mälardalen University.
    Portugal, Paulo José
    University of Porto.
    Exploring alternatives to scale FTT-SE to large networks2011In: 6th IEEE International Symposium on Industrial Embedded Systems, 2011Conference paper (Refereed)
    Abstract [en]

    Nowadays, most complex embedded systems follow a distributed approach in which a network interconnects potentially large numbers of nodes. One technology that is being increasingly used is switched Ethernet, but real-time variants of this protocol typically limit scalability. In this paper, we focus on the scalability of the Flexible Time Triggered communication over Switched Ethernet (FTT-SE), which has been proposed to support hard real-time applications in a flexible and predictable manner. Moreover, time-triggered and event-triggered communication methods are supported in this protocol. FTT-SE has already been explored and investigated for small scale networked applications. In this paper we address the protocol scalability and suggest three different solutions with a qualitative assessment. © 2011 IEEE.

  • 3085. Yeoh, Phee Lep
    et al.
    Elkashlan, Maged
    Duong, Trung Q.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Yang, Nan
    da Costa, Daniel Benevides
    Transmit Antenna Selection for Interference Management in Cognitive Relay Networks2014In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 63, no 7, 3250-3262 p.Article in journal (Refereed)
    Abstract [en]

    We propose transmit antenna selection (TAS) in decode-and-forward (DF) relaying as an effective approach to reduce the interference in underlay spectrum sharing networks with multiple primary users (PUs) and multiple antennas at the secondary users (SUs). We compare two distinct protocols: 1) TAS with receiver maximal-ratio combining (TAS/MRC) and 2) TAS with receiver selection combining (TAS/SC). For each protocol, we derive new closed-form expressions for the exact and asymptotic outage probability with independent Nakagami-m fading in the primary and secondary networks. Our results are valid for two scenarios related to the maximum SU transmit power, i.e., P, and the peak PU interference temperature, i.e., Q. When P is proportional to Q, our results confirm that TAS/MRC and TAS/SC relaying achieve the same full diversity gain. As such, the signal-to-noise ratio (SNR) advantage of TAS/MRC relaying relative to TAS/SC relaying is characterized as a simple ratio of their respective SNR gains. When P is independent of Q, we find that an outage floor is obtained in the large P regime where the SU transmit power is constrained by a fixed value of Q. This outage floor is accurately characterized by our exact and asymptotic results.

  • 3086. 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.

  • 3087.
    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.

  • 3088. 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)
  • 3089.
    Yin, Xiaoyan
    et al.
    Electrical and Computer Engineering Department, Duke University, Durham, NC, USA.
    Ma, Xiaomin
    Department of Engineering and Physics, College of Science and Engineering, Oral Roberts University, Tulsa, OK, USA.
    Trivedi, Kishor S.
    Electrical and Computer Engineering Department, Duke University, Durham, NC, USA.
    Vinel, Alexey
    Tampere University of Technology, Tampere, Finland.
    Performance and Reliability Evaluation of BSM Broadcasting in DSRC with Multi-channel Schemes2014In: I.E.E.E. transactions on computers (Print), ISSN 0018-9340, E-ISSN 1557-9956, Vol. 63, no 12, 3101-3113 p.Article in journal (Refereed)
    Abstract [en]

    IEEE 1609.4 protocol defines a channel switching mechanism to enable a single radio operating efficiently on multiple channels to support both safety and non-safety services. Basic safety message (BSM) is transmitted only through the control channel at regular intervals. In this paper, we propose an analytic model based on interacting semi-Markov process (SMP) to evaluate both Medium Access Control (MAC) and application level performance and reliability of safety message broadcasting incorporating the impact of multichannel operations. Message service time distribution is derived using Laplace-Stieltjes transform based on the proposed model. Due to the cyclic interactions between theSMPmodels for vehicles contending the samechannel, fixed-point iteration is used to obtain converged solutions. Subsequently, MAC and application-level performance and reliability metrics are derived based on the converged solutions. Channel fading with path loss is taken into consideration in this derivation. The analytic models are validated through extensive simulations in NS2 to verify the effectiveness and accuracy of our proposed fixed-point iteration based model decomposition. The effects of channel switching mechanism and channel fading are also evaluated by comparing with other analytic models.

  • 3090. 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)
  • 3091. 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.

  • 3092. 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.

  • 3093.
    You, Lei
    et al.
    Qingdao University, Peoples R China.
    Lei, Lei
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. University of Maryland, MD USA.
    A Performance Study of Energy Minimization for Interleaved and Localized FDMA2014In: 2014 IEEE 19TH INTERNATIONAL WORKSHOP ON COMPUTER AIDED MODELING AND DESIGN OF COMMUNICATION LINKS AND NETWORKS (CAMAD), IEEE , 2014, 16-20 p.Conference paper (Refereed)
    Abstract [en]

    Optimal channel allocation is a key performance engineering aspect in single-carrier frequency-division multiple access (SC-FDMA). It is of significance to consider minimum sum power (Min-Power), subject to meeting specified users demand, since mobile users typically employ battery-powered handsets. In this paper, we prove that Min-Power is polynomial-time solvable for interleaved SC-FDMA (IFDMA). Then we propose a channel allocation algorithm for IFDMA, which is guaranteed to achieve global optimum in polynomial time. We numerically compare the proposed algorithm with optimal localized SC-FDMA (LFDMA) for Min-Power. The results show that LFDMA outperforms IFDMA in the maximal supported user demand. When the user demand can be satisfied in both LFDMA and IFDMA, LFDMA performs slightly better than IFDMA. However MinPower is polynomial-time solvable for IFDMA whereas it is not for LFDMA.

  • 3094.
    You, Lei
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Lei, Lei
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. University of Maryland, MD 20740 USA.
    Optimizing Power and User Association for Energy Saving in Load-Coupled Cooperative LTE2016In: 2016 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    We consider an energy minimization problem for cooperative LTE networks. To reduce energy consumption, we investigate how to jointly optimize the transmit power and the association between cells and user equipments (UEs), by taking into consideration joint transmission (JT), one of the coordinated multipoint (CoMP) techniques. We formulate the optimization problem mathematically. For solving the problem, a dynamic power allocation algorithm that adjusts the transmit power of all cells, and an algorithm for optimizing the cell-UE association, are proposed. The two algorithms are iteratively used in an algorithmic framework to enhance the energy performance. Numerically, the proposed algorithms can lead to lower energy consumption than the optimal energy setting in the non-JT case. In comparison to fixed power allocation in JT, the proposed dynamic power allocation algorithm is able to significantly reduce the energy consumption.

  • 3095.
    You, Lei
    et al.
    Uppsala University, Sweden.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Uppsala University, Sweden.
    Joint CoMP-Cell Selection and Resource Allocation in Fronthaul-Constrained C-RAN2017In: 2017 15TH INTERNATIONAL SYMPOSIUM ON MODELING AND OPTIMIZATION IN MOBILE, AD HOC, AND WIRELESS NETWORKS (WIOPT), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    Cloud-based Radio Access Network (C-RAN) is a promising architecture for future cellular networks, in which Baseband Units (BBUs) are placed at a centralized location, with capacity-constrained fronthaul connected to multiple distributed Remote Radio Heads (RRHs) that are far away from the BBUs. The centralization of signal processing enables the flexibility for coordinated multi-point transmission (CoMP) to meet high traffic demand of users. We investigate how to jointly optimize CoMP-cell selection and base station resource allocation so as to enhance the quality of service (QoS), subject to the fronthaul capacity constraint in orthogonal frequency-division multiple access (OFDMA) based C-RAN. The problem is proved to be NP-hard in this paper. To deal with the computational complexity, we derive a partial optimality condition as the foundation for designing a cell-selection algorithm. Besides, we provide a solution method of the optimum of the time-frequency resource allocation problem without loss of fairness on the QoS enhancement of all users. The simulations show good performance of the proposed algorithms for jointly optimizing the cell selection and resource allocation in a C-RAN, with respect to QoS.

  • 3096.
    Yu, Kan
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    On Reliable and Deadline-Constrained Communication in Wireless Industrial Networks2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Along with the quick development of wireless communication technologies, industrial automation networks are also in unceasing evolution. Industrial wireless sensor and actuator networks (IWSAN) have been increasingly adopted in industrial automation systems. Although there are a number of advantages of replacing cables with wireless links, such as cost reduction, enhanced scalability and flexibility, the stringent requirements on communication reliability and meeting firm deadlines from industrial mission-critical applications must still be fulfilled. Also, transmissions over wireless channels in industrial environments are prone to noise and interferences, resulting in frequent erroneous packet deliveries. Although industrial automation systems are usually designed to be tolerant of certain communication errors, successive transmission failures may still cause downtime of industrial applications, which might lead to significant economic losses or even serious accidents. This thesis addresses the problems mentioned above and aims to provide reliable and deadline-constrained communication via IWSANs for industrial automation systems. On the MAC layer, existing IWSAN standards utilize automatic repeat request (ARQ) to improve reliability at the cost of additional transmission latency. An alternative method is to use Forward Error Correction (FEC) schemes to provide reliable communication by recovering erroneous data and avoiding unnecessary retransmissions. On the MAC layer, Time Division Multiple Access (TDMA) is usually applied in current IWSAN standards for collision-free and deterministic communication. An inappropriate scheduling scheme may introduce high transmission jitter and degrade the quality of control. On the network layer, routing protocols play an important role in both communication reliability and latency. Existing solutions are either hardly able to fulfill all stringent requirements from the mission-critical industrial applications, too complicated to be realized, or lack verification in reality. The contributions of this thesis consist of (i) the possibilities of using FEC schemes in IWSANs is explored under the requirements of existing standards on the MAC layer. A compatible and flexible FEC scheme on the MAC layer for IWSANs that does not violate the standard is proposed and evaluated by simulations. (ii) To guarantee an acceptable control quality, a TDMA scheduling scheme is presented aiming for low communication jitter, and it is compared to classic scheduling schemes. (iii) The advantages of exploiting flooding in IWSANs is discussed; a reliable controlled flooding-based routing protocol is proposed and compared to both traditional routing protocols and other flooding-based protocols. (iv) A complete IWSAN platform is built and the whole protocol stack is implemented. Measurements were conducted in a real industrial environment to verify the correctness of the proposed solution.

  • 3097.
    Yu, Kan
    Mälardalen University, School of Innovation, Design and Engineering.
    On Reliable Real Time Communication in Industrial Wireless Sensor Networks2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the industrial automation, Industrial Wireless Sensor Networks (IWSNs) have been increasingly applied due to a great number of benefits such as convenient installation, flexible deployment and cost efficiency. Compared with conventional wireless systems, IWSNs have more stringent requirements communication reliability and real time performance. However, IWSNs are frequently deployed in a hash industrial environment with electromagnetic disturbances, moving objects and non-line-of-sight (NLOS) communication. Because of the vulnerability of wireless signal, IWSNs are under high risk oftransmission failures, which may result in missing or delaying of process orcontrol data. For industrial automation, missing the process or control deadlineis intolerable, which may terminate industrial application and finally result in economic loss and safety problems. From hierarchy point of view, the high communication reliability and low communication latency can be achieved from different network layers. OnMAC layer, existing protocols in IWSNs only provide automatic repeat request (ARQ) to improve reliability at the cost of real time performance. Analternative method is to apply Forward Error Correction (FEC) mechanism on MAC layer to provide more reliable transmissions and reduce acknowledgement messages by recovering error data. On network layer, routing protocolplays an important role in both communication reliability and latency. Traditionalrouting protocols in IWSNs are either hardly able to fulfill both of these requirements or overcomplicated.In this thesis, we initially explore the possibilities of introducing FEC intoIWSN under the requirements of the existing standard on MAC layer. Then we propose compatible and flexible FEC schemes on MAC layer for IWSNs without violating the standard format. Routing protocols based on flooding are proved to increase the Packet Delivery Ratio (PDR) by transmission diversity.We propose reliable and robust routing protocols with respect to high reliability and real time performance for IWSNs.

  • 3098.
    Yu, Kan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Barac, Filip
    Mid Sweden University.
    Gidlund, Mikael
    ABB, Corporate Research.
    Åkerberg, Johan
    ABB, Corporate Research.
    Adaptive Forward Error Correction for Best Effort Wireless Sensor Networks2012In: 2012 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), 2012, 7104-7109 p.Conference paper (Refereed)
    Abstract [en]

    In this work we propose an Adaptive Forward Error Correction (AFEC) algorithm for best effort Wireless Sensor Networks. The switching model is described in terms of a finite-state Markov model and it is based on the channel behavior,observed via Packet Delivery Ratio in the recent past. We compare the performance of AFEC with static FEC, as well as uncoded transmissions. The results demonstrate a gain in PDR achieved by introducing FEC coding in uncoded IEEE 802.15.4 transmissions, as well as the advantages over static FEC schemes,namely increased throughput and reduced energy consumption.The proposed solution is IEEE 802.15.4-compliant and requires no additional feedback channels.

  • 3099.
    Yu, Kan
    et al.
    Mälardalen University.
    Barac, Filip
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Gidlund, Mikael
    ABB AB, Corporate Research, Sweden.
    Åkerberg, Johan
    ABB AB, Corporate Research, Sweden.
    Björkman, Mats
    Mälardalen University, Sweden.
    A Flexible Error Correction Scheme for IEEE 802.15.4-based Industrial Wireless Sensor Networks2012In: IEEE International Symposium on Industrial Electronics, IEEE conference proceedings, 2012, 1172-1177 p.Conference paper (Refereed)
    Abstract [en]

    Noise and interference make a substantial impacton wireless transmissions in industrial environments, resulting infrequent erroneous packet deliveries. Existing industrial communicationstandards adopt the IEEE 802.15.4 specification, whichprovides no means to correct the detected errors. We proposean IEEE 802.15.4-compliant Forward Error Correction-basedapproach that can be easily retrofitted into the standard withoutthe need for any kind of interaction with chip manufacturers orstandardization bodies. We evaluate the approach on link- andnetwork-level scenarios. Improvement of reliability by using FECcan yield multiple benefits: a reduced number of retransmissions,and lower average latency, to name a few. With respect to theuncoded system, the proposed solution provides identical codinggain as the traditional FEC method, at a significantly lowercomputational load of decoding

  • 3100.
    Yu, Kan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Filip, Barac
    Mid Sweden University.
    Mikael, Gidlund
    ABB, Corporate Research.
    Åkerberg, Johan
    ABB, Corporate Research.
    Mats, Björkman
    Mälardalen University, School of Innovation, Design and Engineering.
    A Flexible Error Correction Scheme for IEEE 802.15.4-based Industrial Wireless Sensor Networks2012In: IEEE International Symposium on Industrial Electronics, 2012, 1172-1177 p.Conference paper (Refereed)
    Abstract [en]

    Noise and interference make a substantial impacton wireless transmissions in industrial environments, resulting infrequent erroneous packet deliveries. Existing industrial communication standards adopt the IEEE 802.15.4 specification, which provides no means to correct the detected errors. We propose an IEEE 802.15.4-compliant Forward Error Correction-basedapproach that can be easily retrofitted into the standard withoutthe need for any kind of interaction with chip manufacturers orstandardization bodies. We evaluate the approach on link- and network-level scenarios. Improvement of reliability by using FEC can yield multiple benefits: a reduced number of retransmissions,and lower average latency, to name a few. With respect to the uncoded system, the proposed solution provides identical codinggain as the traditional FEC method, at a significantly lower computational load of decoding.

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