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  • 3101.
    Zhao, Hao
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Communication Systems, CoS (closed 2012-01-01).
    Muftic, Sead
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Communication Systems, CoS (closed 2012-01-01).
    Zhang, Feng
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Communication Systems, CoS (closed 2012-01-01).
    The secure mobile wallet: Anytime, anywhere financial transactions2010In: Cutter IT Journal, ISSN 1522-7383, Vol. 23, no 7, 32-35 p.Article in journal (Refereed)
  • 3102.
    Zhao, Wang
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Hu, JianHao
    Xiong, Xing Zhong
    Song, Jie
    Non-data-aided timing acquisition for asynchronous IDMA systems2012In: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. AprilArticle in journal (Refereed)
    Abstract [en]

    Sample-timing error can cause significant performance degradation for the interleave-

    division multiple-access systems (Wang et al.2009). In this paper, we propose a nondata-aided timing acquisition scheme tomitigate sample-timing error due to the asynchronoustransmission of random allocated user ends (UEs) on the uplink.Aclosed-loop timing control scheme is constructed for the asynchronous IDMA system in this paper.We use the extrinsic information generated during the iterative detection algorithm with signal noise ratio  volution to estimate the timing offset for the asynchronous uplink in the base station (BS) receiver. The BS receiver returns the timing control bits, which is generated with estimated timing offsets, to the corresponding UE. And the UE uses the timing control bits to adjust local transmission time to guarantee the sampling performance at the BS receiver. The simulation results show that the proposed acquisition scheme based on feedback loop can provide high acquisition probability and low false alarm probability. The proposed scheme can overcome the bit-error-rate performance bottleneck, which is caused by the sample-timing error in BS receiver due to the asynchronous signals in the uplink.

  • 3103.
    Zhao, Wei
    et al.
    Ericsson Research.
    Andersson, Loa
    Ericsson AB.
    Sköldström, Pontus
    Acreo AB.
    Prototyping MPLS-TP forwarding and OAM2009In: 5th International Conference on IP + Optical Network, 2009Conference paper (Refereed)
  • 3104.
    Zhao, Xueqian
    KTH, School of Information and Communication Technology (ICT), Electronics and Embedded Systems.
    Network on Chip: Performance Bound and Tightness2015Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Featured with good scalability, modularity and large bandwidth, Network-on-Chip (NoC) has been widely applied in manycore Chip Multiprocessor (CMP) and Multiprocessor System-on-Chip (MPSoC) architectures. The provision of guaranteed service emerges as an important NoC design problem due to the application requirements in Quality-of-Service (QoS).

    Formal analysis of performance bounds plays a critical role in ensuring guaranteed service of NoC by giving insights into how the design parameters impact the network performance. The study in this thesis proposes analysis methods for delay and backlog bounds with Network Calculus (NC). Based on xMAS (eXecutable Micro-Architectural Specification), a formal framework to model communication fabrics, the delay bound analysis procedure is presented using NC. The micro-architectural xMAS representation of a canonical on-chip router is proposed with both the data flow and control flow well captured. Furthermore, a well-defined xMAS model for a specific application on an NoC can be created with network and flow knowledge and then be mapped to corresponding NC analysis model for end-to-end delay bound calculation. The xMAS model effectively bridges the gap between the informal NoC micro-architecture and the formal analysis model. Besides delay bound, the analysis of backlog bound is also crucial for predicting buffer dimensioning boundary in on-chip Virtual Channel (VC) routers. In this thesis, basic buffer use cases are identified with corresponding analysis models proposed so as to decompose the complex flow contention in a network. Then we develop a topology independent analysis technique to convey the backlog bound analysis step by step. Algorithms are developed to automate this analysis procedure.

    Accompanying the analysis of performance bounds, tightness evaluation is an essential step to ensure the validity of the analysis models. However, this evaluation process is often a tedious, time-consuming, and manual simulation process in which many simulation parameters may have to be configured before the simulations run. In this thesis, we develop a heuristics aided tightness evaluation method for the analytical delay and backlog bounds. The tightness evaluation is abstracted as constrained optimization problems with the objectives formulated as implicit functions with respect to the system parameters. Based on the well-defined problems, heuristics can be applied to guide a fully automated configuration searching process which incorporates cycle-accurate bit-accurate simulations. As an example of heuristics, Adaptive Simulated Annealing (ASA) is adopted to guide the search in the configuration space. Experiment results indicate that the performance analysis models based on NC give tight results which are effectively found by the heuristics aided evaluation process even the model has a multidimensional discrete search space and complex constraints.

    In order to facilitate xMAS modeling and corresponding validation of the performance analysis models, the thesis presents an xMAS tool developed in Simulink. It provides a friendly graphical interface for xMAS modeling and parameter configuring based on the powerful Simulink modeling environment. Hierarchical model build-up and Verilog-HDL code generation are essentially supported to manage complex models and conduct simulations. Attributed to the synthesizable xMAS library and the good extendibility, this xMAS tool has promising use in application specific NoC design based on the xMAS components.

  • 3105. Zhao, Ying
    et al.
    Deng, Lei
    Pang, Xiaodan
    RISE ACREO AB; Technical University of Denmark.
    Yu, Xianbin
    Zheng, Xiaoping
    Zhang, Hanyi
    Monroy, Idelfonso Tafur
    Digital predistortion of 75–110 GHz W-band frequency multiplier for fiber wireless short range access systems2011In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 19, no 26, 18-25 p.Article in journal (Refereed)
    Abstract [en]

    We present a W-band fiber-wireless transmission system based on a nonlinear frequency multiplier for high-speed wireless short range access applications. By implementing a baseband digital signal predistortion scheme, intensive nonlinear distortions induced in a sextuple frequency multiplier can be effectively pre-compensated. Without using costly W-band components, a transmission system with 26km fiber and 4m wireless transmission operating at 99.6GHz is experimentally validated. Adjacent-channel power ratio (ACPR) improvements for IQ-modulated vector signals are guaranteed and transmission performances for fiber and wireless channels are studied. This W-band predistortion technique is a promising candidate for applications in high capacity wireless-fiber access systems.

  • 3106. Zhao, Ying
    et al.
    Pang, Xiaodan
    RISE ACREO AB; Technical University of Denmark.
    Deng, Lei
    Othman, Maisara B
    Yu, Xianbin
    Zheng, Xiaoping
    Zhang, Hanyi
    Monroy, Idelfonso T
    Experimental demonstration of 5-Gb/s polarization-multiplexed fiber-wireless MIMO systems2011In: 2011 IEEE International Topical Meeting on Microwave Photonics - Jointly Held with the 2011 Asia-Pacific Microwave Photonics Conference, MWP/APMP 2011, 2011, 13-16 p., 6088657Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrate a 5-Gb/s fiber-wireless transmission system combining optical polarization-division-multiplexing (PDM) and wireless multiple-input, multiple-output (MIMO) spatial multiplexing technologies. The optical-wireless channel throughput is enhanced by achieving a 4b/s/Hz spectral efficiency. Based on the implementation of constant modulus algorithm (CMA), the 2x2 MIMO wireless channel is characterized and adaptively equalized for signal demodulation. The performance of the CMA-based channel adaptation is studied and it is revealed that the algorithm is particularly advantageous to the MIMO wireless system due to the inter-channel delay insensitivity. The hybrid transmission performance of 26km fiber and up to 2m wireless MIMO is investigated.

  • 3107. Zhao, Ying
    et al.
    Pang, Xiaodan
    RISE ACREO AB; Technical University of Denmark.
    Deng, Lei
    Yu, Xianbin
    Zheng, Xiaoping
    Monroy, Idelfonso Tafur
    Ultra-Broadband Photonic Harmonic Mixer Based on Optical Comb Generation2012In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 24, no 1, 16-18 p., 6045319Article in journal (Refereed)
    Abstract [en]

    We propose a novel photonic harmonic mixer operating at frequencies up to the millimeter-wave (MMW) band. By combining a broadband fiber-wireless signal with high-order harmonics of a fundamental local oscillator in an optical frequency comb generator, frequency down-conversion can be implemented without using a costly ultra-broadband photodiode. It is theoretically shown that the down-conversion efficiency and the bandwidth of the mixer is highly dependent on the optical modulation indices and the fundamental frequency of comb lines. Down-conversion of a W-band (75-110 GHz) fiber-wireless signal is experimentally demonstrated. Moreover, the error vector magnitude (EVM) performance of a multigigabit quadrature phase-shift-keying (QPSK) signal at 62.5-, 82.5-, and 102.5-GHz carrier frequencies is studied to evaluate the down-conversion efficiency. The proposed photonic harmonic mixer can be a candidate for applications in high capacity fiber-wireless communication systems.

  • 3108. Zhao, Ying
    et al.
    Pang, Xiaodan
    RISE ACREO AB; Technical University of Denmark.
    Deng, Lei
    Yu, Xianbin
    Zheng, Xiaoping
    Zhou, Bingkun
    Monroy, Idelfonso Tafur
    High accuracy microwave frequency measurement based on single-drive dual-parallel Mach-Zehnder modulator2011In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 19, no 26, 681-686 p.Article in journal (Refereed)
    Abstract [en]

    A novel approach for broadband microwave frequency measurement by employing a single-drive dual-parallel Mach-Zehnder modulator is proposed and experimentally demonstrated. Based on bias manipulations of the modulator, conventional frequency-to-power mapping technique is developed by performing a two-stage frequency measurement cooperating with digital signal processing. In the experiment, 10GHz measurement range is guaranteed and the average uncertainty of estimated microwave frequency is 5.4MHz, which verifies the measurement accuracy is significantly improved by achieving an unprecedented 10(-3) relative error. This high accuracy frequency measurement technique is a promising candidate for high-speed electronic warfare and defense applications.

  • 3109.
    Zhao, Yuxin
    et al.
    Ericsson Research, Linköping, Sweden.
    Yin, Feng
    Ericsson Research, Linköping, Sweden.
    Gunnarsson, Fredrik
    Ericsson Research, Linköping, Sweden.
    Amirijoo, Mehdi
    Ericsson Research, Linköping, Sweden.
    Hendeby, Gustaf
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Gaussian Process for Propagation modeling and Proximity Reports Based Indoor Positioning2016In: 2016 IEEE 83rd Vehicular Technology Conference (VTC Spring), IEEE , 2016, 1-5 p.Conference paper (Refereed)
    Abstract [en]

    The commercial interest in proximity services is increasing. Application examples include location-based information and advertisements, logistics, social networking, file sharing, etc. In this paper, we consider network-based positioning based on times series of proximity reports from a mobile device, either only a proximity indicator, or a vector of RSS from observed nodes. Such positioning corresponds to a latent and nonlinear observation model. To address these problems, we combine two powerful tools, namely particle filtering and Gaussian process regression (GPR) for radio signal propagation modeling. The latter also provides some insights into the spatial correlation of the radio propagation in the considered area. Radio propagation modeling and positioning performance are evaluated in a typical office area with Bluetooth-Low-Energy (BLE) beacons deployed for proximity detection and reports. Results show that the positioning accuracy can be improved by using GPR.

  • 3110.
    Zhao, Yuxin
    et al.
    Ericsson Research, Linköping, Sweden.
    Yin, Feng
    Ericsson Research, Linköping, Sweden.
    Gunnarsson, Fredrik
    Ericsson Research, Linköping, Sweden.
    Amirijoo, Mehdi
    Ericsson Research, Linköping, Sweden.
    Özkan, Emre
    ISY, Linköping University.
    Gustafsson, Fredrik
    ISY, Linköping University.
    Particle Filtering for Positioning Based on Proximity Reports2015Conference paper (Refereed)
    Abstract [en]

    The commercial interest in proximity services is increasing. Application examples include location-based information and advertisements, logistics, social networking, file sharing, etc. In this paper, we consider positioning of devices based on time series proximity reports from a mobile device to a network node. This corresponds to nonlinear measurements with respect to the device position in relation to the network nodes. Therefore, particle filtering is applicable for positioning. Positioning performance is evaluated in a typical office area with Bluetooth-low-energy beacons deployed for proximity detection and report. Accuracy is concluded to vary spatially over the office floor, and in relation to the beacon deployment density.

  • 3111.
    Zhao, Zhengjian
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Mediating updates using a web based service2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The European Commission had approved the Registration, Evaluation and Authorization of Chemicals (REACH) regulations in the year 2006, and will begin to implement it form 1 June 2007. This regulation greatly increases safety of protection for the users of chemicals, but it also brought a problem for the manufactures as well as downstream users. That is they have to generate and distribute much more Material Safety Data Sheets (MSDS) then before. This work is difficult for most companies since this job usually was done manually. The new regulation requires a much more efficient method to generate and distribute them.

    This thesis project addresses the problem of automatically distributing MSDS and the corresponding metadata. It presents the underlying technology selected for this project. It gives a brief introduction of this project, the underlying technologies used, along with the methods used to deliver relevant and up to date materials safety information.

    At last an HTTP web application approach was selected to solve the problem, the resulting application can efficiently notify a downstream user of the newly updated MSDS and transport the corresponding file and metadata. It is truly data driven, therefore the downstream user does not need to check for updates everyday, instead will be notified when there is an available update.

  • 3112. Zheng, G.
    et al.
    Li, J.
    Wong, K. -K
    Petropulu, A. P.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Using simple relays to improve physical-layer security2012In: Communications in China (ICCC), 2012 1st IEEE International Conference on, IEEE , 2012, 329-333 p.Conference paper (Refereed)
    Abstract [en]

    This paper studies different uses of two cooperating relays to improve the secrecy rate of a wiretap channel. These two relays are assumed to perform only simple functions: either amplify-and-forward (AF) or jamming. Complex functions such as decode-and-forward (DF) are not considered. We study three modes of cooperation: i) cooperative jamming (CJ), ii) AF-aided beamforming and iii) mixed AF-aided beamforming and CJ, all with individual relay power constraints. While i) is known in the literature, our efforts are spent on ii) and iii). In particular, for iii), we assume that the jamming signals in two communication stages are correlated, giving rise to improved performances. We also propose a heuristic approach for selecting the appropriate cooperating mode. Simulation results illustrate the performance gain of each scheme under different channel conditions and the effectiveness of the proposed mode selection method.

  • 3113.
    Zheng, Gan
    et al.
    Department of Electrical and Electronic Engineering, University College London, UK.
    Wong, Kai-Kit
    Department of Electrical and Electronic Engineering, University College London, UK.
    Paulraj, Arogyasvsami
    Information Systems Laboratory, Stanford University, US.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Collaborative-Relay Beamforming with Perfect CSI: Optimum and Distributed Implementation2009In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 16, no 4, 257-260 p.Article in journal (Refereed)
    Abstract [en]

    This letter studies the collaborative use of amplify-and-forward (AF) relays to form a virtual multiple-input single-output (MISO) beamforming system with the aid of perfect channel state information (CSI) in a flat-fading channel. In particular, we optimize the relay weights jointly to maximize the received signal-to-noise ratio (SNR) at the destination terminal with both individual and total power constraints at the relays. We show that the optimal collaborative-relay beamforming (CRB) solution achieves the full diversity of a MISO antenna system. Another main contribution of this letter is a distributed algorithm that allows each individual relay to learn its own weight, based on the Karush-Kuhn-Tucker (KKT) analysis.

  • 3114.
    Zheng, Gan
    et al.
    Department of Electrical and Electronic Engineering, University College London, London, WC1E 7JE, UK..
    Wong, Kai-Kit
    Department of Electrical and Electronic Engineering, University College London, London, WC1E 7JE, UK..
    Paulraj, Arogyasvsami
    Information Systems Laboratory, Stanford University, US.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Robust and distributed beamforming2009In: 2009 International Conference on Wireless Communications and Signal Processing, 2009, Vol. WCSP 2009, 1629-1633 p.Conference paper (Refereed)
    Abstract [en]

    This paper studies the use of amplify-and-forward (AF) relays for robust beamforming, with the aid of imperfect channel state information (CSI) at the sender. In particular, the maximization of the worst-case signal-to-noise ratio (SNR) at the destination terminal is studied under a bounded spherical region for the norm of CSI error vector. We show that under a condition on the estimated CSI quality, the robust-optimal collaborative-relay beamforming (CRBF) can be obtained by S-Procedure and rank relaxation techniques. In addition, a distributed algorithm is proposed by examining the structure of the optimal CRBF.

  • 3115.
    Zheng, Gan
    et al.
    Department of Electrical and Electronic Engineering, University College London.
    Wong, Kai-Kit
    Department of Electrical and Electronic Engineering, University College London.
    Paulraj, Arogyasvsami
    Information Systems Laboratory, Stanford University, US.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Robust Collaborative-Relay Beamforming2009In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 57, no 8, 3130-3143 p.Article in journal (Refereed)
    Abstract [en]

    Relay communications is a promising technique to extend the range of wireless communications by forwarding the message from the sender to the intended destination. While fixed or variable-power relays have been previously investigated, this paper addresses the collaborative use of variable-phase variable-power amplify-and-forward (AF) relays for robust beamforming, with the aid of imperfect channel state information (CSI) at the sender. In particular, the maximization of the worst-case signal-to-noise ratio (SNR) at the destination terminal is studied under a bounded spherical region for the norm of the CSI error vector from the relays to the destination. Our main contribution is that we prove, under a condition on the quality of the estimated CSI, the robust-optimal collaborative-relay beamforming (CRBF) can be obtained by S-Procedure and rank relaxation techniques. In addition, a distributed algorithm is developed by examining the structure of the optimal CRBF solution. Results demonstrate a significant gain of CRBF over non-robust approaches.

  • 3116.
    Zheng, Li-Rong
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Intelligent paper and packaging - Integration of microelectronics technologies into paper and packaging products2007In: International Paperworld IPW, ISSN 1615-1720, no 11, 56-58 p.Article in journal (Other academic)
    Abstract [en]

    The integration of microelectronics technologies and intelligent packaging into the paper and packaging products are creating new business opportunities. Intelligent and interactive packaging aims to make traditional food packaging smart, active and user-friendly. he printed optical code or integrated radio-frequency identification (RFID) chips will allow the customers to link the products directly to mobile Internet through the camera or near field communication. The paper can be used as a paper-based biochip for biochemical analysis by integrating biochemical sensors or a sensor array. VINN Excellence iPack Center has been established with the focus on ubiquitous intelligence in paper and packaging. The center will establish collaborations between the forest products industry, the electronics industry and the biomedical industry in the area of intelligent paper and packaging for biomedical applications.

  • 3117.
    Zheng, Tao
    et al.
    Beijing Jiatong University.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Åkerberg, Johan
    ABB Corporate Research.
    Wireless Arbitration: A Priority-Based Deterministic Media Access Technique for Industrial Wireless Sensor Networks2013Conference paper (Refereed)
  • 3118.
    Zhong, Yang
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Tufvesson, Fredrik
    A dual input-channel software defined receiver platform for GSM WCDMA and Wi-Fi2011In: 2011 International Conference on Wireless Communications and Signal Processing (WCSP), IEEE Communications Society, 2011Conference paper (Refereed)
    Abstract [en]

    In this paper a synchronized dual input-channel multi-mode Software Defined Radio receiver platform that we built originally is presented. The receiver platform compatible with the GSM, WCDMA, and Wi-Fi standards can detect and identify the surrounding base stations and access points. It features wide frequency range, high adaptive sampling rate and especially dual phase coherent receiving channels synchronized both in frequency and time. A detailed structure of the platform and the principle of the software decoders are shown in this paper. Performance of the receiver platform for signal reception is precise and stable. Benefiting from the flexibility of the receiver function, it is not only capable of various functions, such as cognitive radio development and distributed antenna system measurement for academic research, but a dynamic platform for testing new algorithms and ideas.

  • 3119.
    Zhou, Jia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Adding bandwidth specification to a AAA Sever2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Authentication, authorization, and accounting (AAA) are key elements in network security. In many networks, clients can use resources only after they have been authenticated by an authentication server and authorized to use these resources. In some cases the server will also maintain accounting records in order for an operator (a provider of resources) to charge the account/subscriber for using the service. There are four main AAA protocols being used today. Of these RADIUS is the mostly widely used.

    This thesis starts with an introduction to AAA protocols, and then goes in the details of RADIUS. In order to perform a practical evaluation of how the AAA could be improved, FreeRADIUS was selected as the base code for this project; because this implementation is one of the most widely used RADIUS servers. A proposal for how to improve AAA performance is introduced and the implementation steps needed to realize these improvements are shown. Additionally, some experiments have been conducted to show both the correct functioning of the resulting implementation and to examine if there is a performance improvement. Following this some conclusions are drawn based upon a comparison with a traditional AAA server.

    A key element of the change in AAA which is proposed is the use of a non-binary IEEE 802.1x process. This new non-binary solution introduces a new type of AAA server and requires the re-thinking of a number of traditional AAA design decisions. It is expected that this change will have a significant impact, but will require some time for exposure, implementation by others, and a more extensive evaluation that was possible during the period of this thesis project.

    One of the most important conclusions drawn during this thesis is the difficulty of making a change in authentication and authorization, because of the large amount of interaction between both the various protocols and the standards which have been developed for these protocols. Thus one of the difficult aspects of the task is how to introduce a change in a protocol while maintaining backward compatibility for others who have not adopted this change -- without requiring the addition of a protocol version field.

    A second important conclusion is that doing this implementation in three separate parts with different students being responsible for the different parts revealed just how complex the interaction of protocol design decisions are. While a working version of the entire set of changes proved to be impossible, it was observed that the different parts could be decoupled more than initially expected.

  • 3120.
    Zhou, Jinglong
    et al.
    Delft University of Technology.
    Jacobsson, Martin
    Delft University of Technology.
    Onur, Ertan
    Delft University of Technology.
    Niemegeers, Ignas
    Delft University of Technology.
    An Investigation of Link Quality Assessment for Mobile Multi-hop and Multi-rate Wireless Networks2012In: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 65, no 2, 405-423 p.Article in journal (Refereed)
    Abstract [en]

    Wireless ad hoc networks will be an important component in future communication systems. The performance of wireless ad hoc networks can be improved by link quality-aware applications. Wireless link quality is dynamic in nature, especially in mobile scenarios. Therefore, accurate and fast packet delivery ratio estimation is a prerequisite to good performance in mobile, multi-hop and multi-rate wireless ad hoc networks. In this paper, we propose a novel packet delivery ratio estimation method that improves the accuracy and responsiveness of the packet delivery ratio estimation. The proposed link quality estimation components are implemented in a IEEE 802.11b/g test-bed. The experiment results show that the accuracy of the packet delivery ratio estimation can improve up to 50% in mobile scenarios without introducing overhead. We also show the end-to-end performance impact of this improved estimation on route selection using different routing metrics and configurations. The measurement results show that our packet delivery ratio method leads to better route selection in the form of increased end-to-end throughput compared to traditional methods, which respond slowly to the link dynamics.

  • 3121. Zhou, Jinglong
    et al.
    Jacobsson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Onur, Ertan
    Niemegeers, Ignas
    An investigation of link quality assessment for mobile multi-hop and multi-rate wireless networks2012In: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 65, no 2, 405-423 p.Article in journal (Refereed)
    Abstract [en]

    Wireless ad hoc networks will be an important component in future communication systems. The performance of wireless ad hoc networks can be improved by link quality-aware applications. Wireless link quality is dynamic in nature, especially in mobile scenarios. Therefore, accurate and fast packet delivery ratio estimation is a prerequisite to good performance in mobile, multi-hop and multi-rate wireless ad hoc networks. In this paper, we propose a novel packet delivery ratio estimation method that improves the accuracy and responsiveness of the packet delivery ratio estimation. The proposed link quality estimation components are implemented in a IEEE 802.11b/g test-bed. The experiment results show that the accuracy of the packet delivery ratio estimation can improve up to 50% in mobile scenarios without introducing overhead. We also show the end-to-end performance impact of this improved estimation on route selection using different routing metrics and configurations. The measurement results show that our packet delivery ratio method leads to better route selection in the form of increased end-to-end throughput compared to traditional methods, which respond slowly to the link dynamics.

  • 3122. Zhou, Li
    et al.
    Hu, Xiping
    Ngai, Edith C.-H.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Zhao, Haitao
    Wang, Shan
    Wei, Jibo
    Leung, Victor C. M.
    A dynamic graph-based scheduling and interference coordination approach in heterogeneous cellular networks2016In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 65, no 5, 3735-3748 p.Article in journal (Refereed)
  • 3123. Zhu, Chunsheng
    et al.
    Leung, Victor C. M.
    Shu, Lei
    Ngai, Edith C.-H.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Green Internet of Things for Smart World2015In: IEEE Access, E-ISSN 2169-3536, Vol. 3, 2151-2162 p.Article in journal (Refereed)
    Abstract [en]

    Smart world is envisioned as an era in which objects (e.g., watches, mobile phones, computers, cars, buses, and trains) can automatically and intelligently serve people in a collaborative manner. Paving the way for smart world, Internet of Things (IoT) connects everything in the smart world. Motivated by achieving a sustainable smart world, this paper discusses various technologies and issues regarding green IoT, which further reduces the energy consumption of IoT. Particularly, an overview regarding IoT and green IoT is performed first. Then, the hot green information and communications technologies (ICTs) (e.g., green radio frequency identification, green wireless sensor network, green cloud computing, green machine to machine, and green data center) enabling green IoT are studied, and general green ICT principles are summarized. Furthermore, the latest developments and future vision about sensor cloud, which is a novel paradigm in green IoT, are reviewed and introduced, respectively. Finally, future research directions and open problems about green IoT are presented. Our work targets to be an enlightening and latest guidance for research with respect to green IoT and smart world.

  • 3124.
    Zhu, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Nordström, Lars
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Hammouri, A.
    Jordan University of Science and Technology .
    Examination of data delay and packet loss for wide-area monitoring and control systems2012In: 2012 IEEE International Energy Conference and Exhibition, ENERGYCON 2012, IEEE , 2012, 927-934 p.Conference paper (Refereed)
    Abstract [en]

    Timely and synchronized phasor data at high resolutions holds a great promise for more responsible and advanced power grid operations. It is expected that the combined effort of developing new application paradigms and the supporting Information and Communication Technology (ICT) will enable the evolutionary change for future transmission grid operation. This paper addresses the design of the supporting ICT system for Wide-Area Monitoring and Control applications considering system performance. The major contribution that distinguishes this paper from previous research efforts in the same area is that this study quantifies the end-to-end data delay and the received packet rate with considerations of different levels of data concentrations. The analysis performed in this paper is not merely limited to the performance issues caused by communication networks but also provides means to view and analyze the overall data delay of the entire supporting ICT system.

  • 3125.
    Zhu, Wanning
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Multipoint Relay flooding: Network coding improvements2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Network coding is a new research area with potential to reduce network resources. With network coding, intermediate nodes forward packets that are linear combinations of previously received packets.

    The type of networks we consider are vehicle mounted mobile tactical radio networks. Tactical communication may be required in areas where pre-deployed base stations are unavailable. Mobile ad hoc networks satisfy this requirement. Due to low antenna heights, network resources are scarce inmobile networks without base stations. Broadcast traffic, which disseminates information network-wide, is very important in tactical mobile networks. Multipoint relay flooding is a well-known technique for efficient distribution of broadcast traffic. It is therefore interesting to evaluate how much network coding can reduce the number of transmissions in a mobile ad hoc network. In this thesis we show that it is possible to further reduce the number of transmissions for Multipoints Relay flooding by using network coding. However, this improvement is largely theoretical - there has been no effort to evaluate this approach in practice.

  • 3126. Zhu, Xuncheng
    et al.
    Ding, Zhizhong
    Punyal, Oscar
    Gross, James
    Design and Implementation of Baseband Algorithms for OFDM-based Wireless Communication Systems2011In: 7th International Conference on Wireless Communications, Networking and Mobile Computing (WiCOM), 2011, IEEE conference proceedings, 2011, 1-5 p.Conference paper (Refereed)
    Abstract [en]

    Orthogonal frequency-division multiplexing (OFDM) is an appropriate solution to combat inter-symbol interference (ISI) caused by multi-path propagation in wireless communications. OFDM-based wireless communication systems become more and more popular and the base-band algorithm is one of the significant parts of the systems. In this paper, we present the design and implementation of base-band algorithms for OFDM-based wireless communication systems. The results show that the designed algorithms are effective for implementation of the system.

  • 3127.
    Zhuang, Weihua
    et al.
    University of Waterloo, Ontario, Canada.
    Jamalipour, Abbas
    University of Sydney, Sydney, New South Wales, Australia.
    Bai, Fan
    Carnegie Mellon University, Pittsburgh, Pennsylvania, USA.
    Vinel, Alexey
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Emerging Technologies, Applications, and Standardizations for Connecting Vehicles: [From the Guest Editors]2015In: IEEE Vehicular Technology Magazine, ISSN 1556-6072, E-ISSN 1556-6080, Vol. 10, no 4, 33-35 p.Article in journal (Refereed)
    Abstract [en]

    The articles in this special section focus on the state of the art in the emerging technology for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications, the latest development in standardizations and regulations, and potential services and applications for vehicles on roads. © Copyright 2015 IEEE

  • 3128.
    Zhuang, Weihua
    et al.
    Department of Electrical and Computer Engineering, University of Waterloo, ON, Canada.
    Jamalipour, Abbas
    University of Sydney, Sidney, Australia.
    Bai, Fan
    Caign, Universitarnegie Mellon University, University of Illinois at Urbana-Champy of Southern California, United States.
    Vinel, Alexey
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Emerging Technologies, Applications, and Standardizations for Connecting Vehicles (Part II)2017In: IEEE Vehicular Technology Magazine, ISSN 1556-6072, E-ISSN 1556-6080, Vol. 12, no 2, 23-25 p.Article in journal (Other (popular science, discussion, etc.))
  • 3129. Zibar, Darko
    et al.
    Caballero, Antonio
    Yu, Xianbin
    Pang, Xiaodan
    RISE ACREO AB; Technical University of Denmark.
    Dogadaev, Anton K
    Monroy, I Tafur
    Hybrid optical fibre-wireless links at the 75–110 GHz band supporting 100 Gbps transmission capacities2011In: 2011 IEEE International Topical Meeting on Microwave Photonics - Jointly Held with the 2011 Asia-Pacific Microwave Photonics Conference, MWP/APMP 2011, 2011, 445-449 p., 6088767Conference paper (Refereed)
    Abstract [en]

    We present a photonic generation and down-conversion method for realizing a 40Gbps wireless link at the 75-110 GHz band exploiting the recent advances in photonic coherent detection technologies and digital signal processing. Furthermore, we analyze the capacities of hybrid optical fiber-wireless links at the 75-110GHz band, and propose several approaches to overcome the challenges towards 100Gbps wireless capacity.

  • 3130.
    Zielinski, Andrea
    et al.
    Fraunhofer IOSB, Germany.
    Bock, Jürgen
    FZI Forschungszentrum Informatik, Germany.
    Heberle, Florian
    Karlsruhe University of Applied Sciences, Germany.
    Henning, Peter A.
    Karlsruhe University of Applied Sciences, Germany.
    Kohen-Vacs, Dan
    HIT Holon Institute of Technology, Israel.
    Enhanced e-Learning Experience by Pushing the Limits of Semantic Web Technologies2014In: Proceedings of the 3rd International Workshop on Ordering and Reasoning Co-located with the 13th International Semantic Web Conference (ISWC 2014): Riva del Garda, Italy, October 20th, 2014 / [ed] Irene Celino, Oscar Corcho, Daniele Dell'Aglio, Emanuele Della Valle, Markus Krötzsch, Stefan Schlobach, Italy: CEUR-WS , 2014, 23-34 p.Conference paper (Refereed)
    Abstract [en]

    We investigate a novel approach to e-Learning using Seman-tic Web technologies and aiming to optimise the learners’ experience incorporating pedagogical strategies into the learning process. The in-creasing availability of Semantic Web based educational resources and the establishment of open metadata standards like IEEE LOM pave the way for enhanced e-Learning systems that support personalised learning based on a reasoning framework and formal ontologies. We use ontologies to describe learning objects and the learner state, and define pedagogi-cal recommendation axioms that specify which learning objects are best suited for the learner in a specific situation. Recent pedagogical findings suggest that the individual learning can be optimised by means of guid-ance through learning pathways, i. e., a particular order in which learning objects are to be studied. To this end, we offer an OWL model for learn-ing pathways as structured sequences. We show the strengths and limits of OWL and propose a solution to overcome problems such as handling of soft constraints and ranking of result sets. The calculation for ranking is based on individual weights for specific learner-related features and considers the degree of match between learning objects and learner’s needs. The feasibility of our approach is shown by modelling real-life course material, i.e. a complete course on the Philosophy of Didactics. We implemented our approach as a prototype system and interfaced it to a standard Learning Management System.

  • 3131. Zimmerling, Marco
    et al.
    Ferrari, Federico
    Mottola, Luca
    Voigt, Thiemo
    SICS.
    Thiele, Lothar
    pTunes: runtime parameter adaptation for low-power MAC protocols2012In: IPSN, 2012, 173-184 p.Conference paper (Refereed)
  • 3132.
    Zografos, Alexandros
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Wireless Sensor-based Agricultural Monitoring System2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today energy resources are becoming scarcer and therefore more valuable. In conjunction with the population growth over last century, the need for finding new, more efficient, and sustainable methods of agricultural cultivation and food production has become more critical. To facilitate this process, we are designing, building, and evaluating a system for precision agriculture which provides farmers with useful data about the soil, the water supply, and the general condition of their fields in a user friendly, easily accessible manner. Our system aims to make cultivation and irrigation more efficient as the farmer is able to make better informed decisions and thus save time and resources.

    The diversity of location and climatic effects upon agricultural cultivation, along with other environmental parameters over time makes the farmer’s decision-making process more complicated and requires additional empirical knowledge. Applying wireless sensor networks for monitoring environmental parameters and combining this information with a user-customized web service may enable farmers to exploit their knowledge in an efficient way in order to extract the best results from their agricultural cultivation. The system can scale based on each farmer’s demands and the resulting ensemble of collected information may represent a valuable resource for future use, in addition to its use for real-time decision making. The design of the precision agriculture system contains a prototype solution regarding the sensor platform and a customizable service that can be utilized in different ways and by several entities.

  • 3133.
    Zou, Zhenhua
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Deadline-constrained maximum reliability packet forwarding with limited channel state information2013In: 2013 IEEE Wireless Communications and Networking Conference (WCNC), New York: IEEE Communications Society, 2013, 1721-1726 p.Conference paper (Refereed)
    Abstract [en]

    This paper considers real-time packet forwarding over wireless multi-hop networks with lossy and bursty links. Our objective is to maximize the probability that individual packets reach their destination before a hard deadline. The loss processes on links are modeled by finite-state Markov chains. While the parameters of the Markov chains are assumed to be known, the instantaneous channel states are not accessible but have to be estimated from observations of successes and failures of actual packet transmissions. We formulate the forwarding problem as a partially observable Markov decision process and derive the optimal forwarding policy. A novel technique, based on maximum-volume inscribed ellipsoids, for computing approximate solutions with reduced implementation complexity is proposed. We further discuss structural properties of the value function and the optimal actions. Finally, numerical examples illustrate the power of the developed techniques.

  • 3134.
    Zou, Zhuo
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Impulse Radio UWB for the Internet-of-Things: A Study on UHF/UWB Hybrid Solution2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This dissertation investigates Ultra-Wideband (UWB) techniques for the next generation Radio Frequency Identification (RFID) towards the Internet-of-Things (IoT). In particular, an ultra-high frequency (UHF) wireless-powered UWB radio (UHF/UWB hybrid) with asymmetric links is explored from system architecture to circuit implementation.

    Context-aware, location-aware, and energy-aware computing for the IoT demands future micro-devices (e.g., RFID tags) with capabilities of sensing, processing, communication, and positioning, which can be integrated into everyday objects including paper documents, as well as food and pharmaceutical packages. To this end, reliable-operating and maintenance-free wireless networks with low-power and low-cost radio transceivers are essential. In this context, state-of-the-art passive RFID technologies provide limited data rate and positioning accuracy, whereas active radios suffer from high complexity and power-hungry transceivers. Impulse Radio UWB (IR-UWB) exhibits significant advantages that are expected to overcome these limitations. Wideband signals offer robust communications and high-precision positioning; duty-cycled operations allow link scalability; and baseband-like architecture facilitates extremely simple and low-power transmitters. However, the implementation of the IR-UWB receiver is still power-hungry and complex, and thus is unacceptable for self-powered or passive tags.

    To cope with μW level power budget in wireless-powered systems, this dissertation proposes an UHF/UWB hybrid radio architecture with asymmetric links. It combines the passive UHF RFID and the IR-UWB transmitter. In the downlink (reader-tag), the tag is powered and controlled by UHF signals as conventional passive UHF tags, whereas it uses an IR-UWB transmitter to send data for a short time at a high rate in the uplink (tag-reader). Such an innovative architecture takes advantage of UWB transmissions, while the tag avoids the complex UWB receiver by shifting the burden to the reader. A wireless-powered tag providing -18.5 dBm sensitivity UHF downlink and 10 Mb/s UWB uplink is implemented in 180 nm CMOS. At the reader side, a non-coherent energy detection IR-UWB receiver is designed to pair the tag. The receiver is featured by high energy-efficiency and flexibility that supports multi-mode operations. A novel synchronization scheme based on the energy offset is suggested. It allows fast synchronization between the reader and tags, without increasing the hardware complexity. Time-of-Arrival (TOA) estimation schemes are analyzed and developed for the reader, which enables tag localization. The receiver prototype is fabricated in 90 nm CMOS with 16.3 mW power consumption and -79 dBm sensitivity at 10 Mb/s data rate. The system concept is verified by the link measurement between the tag and the reader. Compared with current passive UHF RFID systems, the UHF/UWB hybrid solution provides an order of magnitude improvement in terms of the data rate and positioning accuracy brought by the IR-UWB uplink.

  • 3135. Zu, L.
    et al.
    Ji, Y.
    Wang, Liping
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Zhong, L.
    Liu, F.
    Wang, P.
    Xu, J.
    Joint optimization in multi-user MIMO-OFDMA relay-enhanced cellular networks2011In: 2011 IEEE Wireless Communications and Networking Conferenc, 2011, 13-18 p.Conference paper (Refereed)
    Abstract [en]

    MIMO, OFDMA and cooperative relaying are the key technologies in future wireless communication systems. However, under the usage of these technologies, resource allocation becomes a more crucial and challenging task. In multi-user MIMO-OFDMA relay-enhanced cellular networks, we formulate the optimal instantaneous resource allocation problem including user group selection, path selection, power allocation, and subchannel scheduling to maximize system capacity. We first propose a low-complex resource allocation algorithm named CP-CP under constant uniform power allocation and then use a water-filling method named CP-AP to allocate power among transmitting antennas. Moreover, we solve the original optimization problem efficiently by using the Jensen's inequality and propose a modified iterative water-filling algorithm named AP-CP. Based on AP-CP, the AP-AP algorithm is proposed to allocate power adaptively not only among subchannels but also among multiple transmitting. Finally, we compare the performance of the four schemes. Our results show that allocating power among subchannels is more effective than among transmitting antennas if the average signal-to-noise radio of users is low, and vice versa. Furthermore, the AP-AP algorithm achieves the highest throughout especially for users near the cell edge.

  • 3136. Zuniga, Marco
    et al.
    Irzynska, Izabela
    Hauer, Jan-Hinrich
    Voigt, Thiemo
    SICS.
    Boano, Carlo Alberto
    Römer, Kay
    Link quality ranking: Getting the best out of unreliable links2011In: DCOSS, 2011, 1-8 p.Conference paper (Refereed)
  • 3137.
    Ängskog, Per
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences. University of Gävle, Center for RF Measurement Technologies.
    Chilo, José
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences. University of Gävle, Center for RF Measurement Technologies.
    Stenumgaard, Peter
    FOI.
    Limitations of WLAN IEEE 802.11 in Industrial Environments2012Conference paper (Refereed)
  • 3138.
    Åhman, Stefan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Wallstersson, Marcus
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    EVH2 protocol: Performance analysis and Wireshark dissector development2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    EVH2 is a proprietary application layer protocol developed by Aptilo Networks and used in their software product. Currently the only way to inspect EVH2 traffic is by using their own application. This application inspects no traffic other than EVH2. Since Aptilo continuously develops this protocol it is important to see how changes in the protocol affect its performance. This thesis examines possible ways to facilitate the use and development of the protocol.

    To analyse EVH2 network traffic along with traffic from other protocols another approach is needed. Wireshark is an application capable of inspecting traffic of multiple protocols simultaneously and uses dissectors to decode each packet. This thesis describes the development and evaluation of a Wireshark plugin dissector for inspection of EVH2 traffic.

    Performance tests of EVH2 will provide feedback about protocol changes. This thesis creates a platform for performance evaluation by introducing a test suite for performance testing. A performance evaluation of EVH2 was conducted using the developed test suit.

  • 3139.
    Åkerberg, Johan
    et al.
    ABB Corporate Research.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Lennvall, Tomas
    ABB Corporate Research.
    Landernäs, Krister
    ABB Corporate Research.
    Björkman, Mats
    Mälardalen University.
    Design Challenges and Objectives in Industrial Wireless Sensor Networks2013In: Industrial Wireless Sensor Networks: Applications, Protocols, Standards, and Products / [ed] V. C. Gungor and G. P. Hancke, CRC Press, 2013Chapter in book (Refereed)
  • 3140.
    Åkervik, Mattias
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Network Gaming: Performance and Traffic Modeling2006Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There are several different types of games that are played in multiplayer mode over networks. The type of network games that, from a network’s perspective, are the most demanding is real-time based multiplayer games. Users of such games both assume and require that game play interaction happens in near real-time and these games often support a large number of simultaneous players. Most networks are specialized to either voice traffic (such as the first and second generation of mobile networks) or data traffic (such as wired data networks). It is not clear that the requirements for such real time games can always be met on either type of network. The core of this thesis investigates the performance requirements real-time multiplayer games place on packet switched data networks and the connection between network impairments and game quality degradation. Traffic generated by network games distinguishes itself from other traffic both regarding its general characteristics and the requirements it places on the network. Understanding these traffic characteristics, requirements, and what consequences failures to support such requirements entail are of great importance when designing new networks in order to guarantee suitable quality of service for such real-time games.

  • 3141.
    Ålemark, Niklas
    KTH, Superseded Departments, Teleinformatics.
    Specification and development of animage acquisition and processing systemwith IR communications capabilities1996Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The GSM network has experienced a fast growth after its introduction in 1992. A large number of users in several countries in the word now have access to a standardised digital cellular network. This fact has lead to that the network is being used for several other things than voice communications. One such application is the transfer of pictures. This requires a unit that can digitise pictures and adapt the digital image information to the characteristics of the GSM network.

    This report describes the specification and development of an image acquisition and processing system with IR communications capabilities. It also outlines some of the possible applications for such a system.

  • 3142.
    Åman, Erik
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A Distributed Cachefor Very Large Objects2001Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Within a few years’ time, the Internet is expected to be used to transfer highquality video material and other bandwidth-demanding objects to a much larger extent than today. Users would prefer to be able to access such very large objects at an arbitrary point in time without any kind of preparation or advance planning. Offering such services on a large scale puts high demands on the network.

    Using a caching Web proxy server may increase the bandwidth and reliability perceived by the users while reducing the load on the network. This can be done transparently to the users.

    This thesis presents the principles for a caching Web proxy server better adapted to this expected traffic pattern. The bandwidth usage and transfer rate can be improved by taking advantage of the longer persistence of connections and by assuming that comparatively few objects will be popular at any given time. An experimental implementation has been developed in order to test the main principles. The new server is designed to operate in a distributed fashion by employing several cooperating servers at strategic points in the network. The system optimizes reliability and throughput by dynamically selecting from where to download objects based on current traffic and previous statistics.

  • 3143.
    Åstrand, Erik
    University of Skövde, School of Informatics.
    Rendering och manipulering av dom: Undersökning av AngularJS och ReactJS2016Independent thesis Basic level (university diploma), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Webben växer och webbapplikationer blir mer och mer komplexa och innehållsrika. Med detta så ska dessa växande applikationer även kunna presenteras på ett tilltalande och effektivt sätt. Jättarna Facebook, Twitter, Instagram och små bloggar har alla börjat använda sig av en teknik för att kunna dynamiskt ladda in ytterligare innehåll på en sida utan att behöva ladda om den. Denna teknik kallas för Infinite Scroll eller oändlig scrollning. Infinite Scroll kan resultera i enormt stort innehåll vilket tidigare studier visar på att det bidrar till bristande prestanda för rendering och manipulering av innehållet. Arbetet kommer utföra ett experiment där målet är att undersöka hur två populära SPA-ramverk AngularJS och ReactJS hanterar detta problem. 

  • 3144.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Dimarogonas, Dino V.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Family of controllers for attitude synchronization in S22016In: Proceedings of the IEEE Conference on Decision and Control, IEEE conference proceedings, 2016, 6761-6766 p.Conference paper (Refereed)
    Abstract [en]

    In this paper we study a family of controllers that guarantees attitude synchronization for a network of elements in the unit sphere domain, i.e., S2. We propose distributed continuous controllers for elements whose dynamics are controllable (i.e., control with torque as command), and which can be implemented by each individual agent without the need of a common global orientation frame among the network, i.e., it requires only local information that can be measured by each individual agent from its own orientation frame. The controllers are specified according to arbitrary distance functions in S2, and we provide conditions on those distance functions that guarantee that i) a synchronized network of agents is locally asymptotically stable for an arbitrary connected network topology; ii) a synchronized network can be achieved for almost all initial conditions in a tree graph network. We also study the equilibria configurations that come with specific types of network graphs. The proposed strategies can be used in attitude synchronization of swarms of fully actuated rigid bodies, such as satellites.

  • 3145.
    Ögren, Niklas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Selecting/realization of Virtual Private Networks with Multiprotocol Label Switching or Virtual Local Area Networks2002Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Many reports have been written about the techniques behind Virtual Private Networks (VPN) and Multi Protocol Label Switching (MPLS). They usually deal with the low level design of the software implementing a specific technique. The initial products are usually not mature enough to run in a large network or have to be adjusted in some way to fit.

    This report investigates the different ways of implementing strict layer 2 Virtual Private Networks in an existing nation-wide Gigabit Ethernet. The infrastructure in use, as well as the hardware, has to be used without major changes. Since 1998/1999, when MPLS first started in the laboratories, development has continued. Today it is possible to introduce MPLS or tunneled national virtual local area network into an existing network. This requires high speed, fault tolerant, and stable hardware and software.

    Going beyond the separation of traffic at layer 3 using Virtual Private Networks, i.e., IPSec, we can tunnel layer 2 traffic through a network. Although the first layer 3 VPN products are already in use, layer 2 VPNs still need to be evaluated and brought into regular use. There are currently two ways of tunneling VLANs in a core network: tunneled VLANs (or as Extreme Networks calls them, VMANs) and MPLS.

    This project showed that it is possible to start with a VLAN-only solution, and then upgrade to MPLS to solve scalability issues. The VMAN solution can not be used at Arrowhead, since there are too many disadvantages in the way Extreme Networks has implemented it. However, a mix of tunneling VMAN in a VLAN core is possible, and enables customer tagging of VLANs in a Layer 2 VPN. Furthermore, the testing of EAPS and per-VLAN Spanning Tree Protocol turned out well, and showed that EAPS should not be used when there is more than one loop.

  • 3146.
    Örn, Daniel
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Szilassy, Martin
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Dil, Bram
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    A Novel Multi-Step Algorithm for Low-Energy Positioning Using GPS2016In: Fusion 2016, 19th International Conference on Information Fusion: Proceedings, 2016, 1469-1476 p.Conference paper (Refereed)
    Abstract [en]

    GPS is widely used for localization and tracking, however traditional GPS receivers consume too much energy for many applications. This paper implements and evaluates the performance of a low-energy GPS prototype. The main difference is that a traditional GPS needs to sample signals transmitted by satellites for 30 seconds to estimate its position. Our prototype reduces this time by three orders of magnitude and it can compute positions from only 2 milliseconds of data. We present a new algorithm that increases robustness by filtering on estimated residuals instead of using an altitude database. In addition, we show that our new algorithm works with both fixed and moving targets. The solution consists of (1) a portable device that samples the GPS signal and (2) a server that utilizes Doppler navigation and Coarse Time Navigation to estimate positions. We performed tests in a wide variety of environments and situations. These tests show that our prototype provides a median positioning error of roughly 40 meters even when the GPS receiver is moving at 80 kilometres per hour.

  • 3147.
    Örn, Sara
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Realistic Multi-Cell Interference Coordination in 4G/LTE2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the LTE mobile system, all cells use the same set of frequencies. This means that a user could experience interference from other cells. A method that has been studied in order to reduce this interference and thereby increase data rate or system throughput is to coordinate scheduling between cells. Good results of this have been found in different studies. However, the interference is generally assumed to be known. Studies using estimated interference and simulating more than one cluster of cells have found almost no gain.

    This thesis will focus on how to use information from coordinated scheduling and other traffic estimates to do better interference estimation and link adaption. The suggested method is to coordinate larger clusters and use the coordination information, as well as estimates of which cells will be transmitting, to make estimates of interference from other cells. The additional information from interference estimation is used in the link adaptation. Limitations in bandwidth of the backhaul needed to send data between cells are considered, as well as the delay it may introduce. A limitation of the scope is that MIMO or HetNet scenarios have not been simulated.

    The suggested method for interference estimation and link adaptation have been implemented and simulated in a system simulator. The method gives a less biased estimate of SINR, but there are no gains in user bit rate. The lesser bias is since the method is better at predicting high SINR than the base estimate is. The lack of gains regarding user bit rate may result from the fact that in the studied scenarios, users where not able to make use of the higher estimated SINR since the base estimate is already high.

    The conclusion is that the method might be useful in scenarios where there are not full load, but the users either have bad channel quality or are able to make use of very high SINR. Such scenarios could be HetNet or MIMO scenarios, respectively.

  • 3148.
    Österberg, Per
    University West, Department of Economics and IT, Division of Computer Engineering.
    A comparison between NS-2 and reality utilizing on queuing disciplines2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Eftersom dagens olika datornätverk växer sig större och mer komplexa har möjligheten att testa ny nätverksfunktionalitet försvårats. Detta har gjort att simulation har blivit populärt ibland utvecklare och forskare inom nätverksområdet. Nätverkssimulatorn NS-2 är en populär simulator som används flitigt av forskare och utvecklare runt om i världen. Men kan vi lita på att NS-2 simulatorns funktionalitet stämmer överens med verklighetens?Denna studie undersöker hur väl ett scenario i NS-2 simulatorn stämmer överens med ett verkligt scenario av samma typ. Vi har använt oss av ett topologi med en flaskhals där vi har testat tre olika kösystem på den strypta länken: Fair queuing, Random early detection och First in first out med Drop Tail. Genom flaskhalsen har vi skickat en UDP ström tillsammans med olika typer av trafik och mätt påverkan på UDP strömmen i form av tappade paket och genomströmning. Resultatet ifrån NS-2 simulatorn är sedan jämnfört med resultat ifrån samma scenario uppsatt i verkligheten.

  • 3149.
    Österlind, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computer Systems. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Improving Low-Power Wireless Protocols with Timing-Accurate Simulation2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Low-power wireless technology enables numerous applications in areas from environmental monitoring and smart cities, to healthcare and recycling. But resource-constraints and the distributed nature of applications make low-power wireless networks difficult to develop and understand, resulting in increased development time, poor performance, software bugs, or even network failures. Network simulators offer full non-intrusive visibility and control, and are indispensible tools during development. But simulators do not always adequately represent the real world, limiting their applicability.

    In this thesis I argue that high simulation timing accuracy is important when developing high-performance low-power wireless protocols. Unlike in generic wireless network simulation, timing becomes important since low-power wireless networks use extremely timing-sensitive software techniques such as radio duty-cycling. I develop the simulation environment Cooja that can simulate low-power wireless networks with high timing accuracy.

    Using timing-accurate simulation, I design and develop a set of new low-power wireless protocols that improve on throughput, latency, and energy-efficiency. The problems that motivate these protocols were revealed by timing-accurate simulation. Timing-accurate software execution exposed performance bottlenecks that I address with a new communication primitive called Conditional Immediate Transmission (CIT). I show that CIT can improve on throughput in bulk transfer scenarios, and lower latency in many-to-one convergecast networks. Timing-accurate communication exposed that the hidden terminal problem is aggravated in duty-cycled networks that experience traffic bursts. I propose the Strawman mechanism that makes a radio duty-cycled network robust against traffic bursts by efficiently coping with hidden terminals.

    The Cooja simulation environment is available for use by others and is the default simulator in the Contiki operating system since 2006.

  • 3150.
    Östh, Joakim
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Study of Six-Port Modulators and Demodulators for High-Speed Data Communications2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    There is an increasing demand for high-speed wireless data communications to support consumers’ need for, among other things, real time streaming of high definition video and fast file transfers. One radio architecture that has a potential to meet the increasing demand for high-speed data communications is a radio technique based on the six-port architecture. In addition to high-speed, the six-port radio also allows low power consumption and low cost. In this thesis, a comprehensive study of the six-port radio technique for high data rate (> 1 Gbit/s) and low complexity are presented.

    Firstly, a technique to suppress the carrier leakage was proposed, analyzed and verified by measurements. The proposed technique uses only a phase shifting network between the six-port correlator and its variable impedance loads, hence it is easy to implement. When the proposed carrier leakage suppression technique is used together with differential control signals, it also has the benefit of both improving the linearity and increasing the output power of the modulator. The same carrier leakage suppression technique can also be used in a six-port demodulator (receiver) to improve its performance.

    Secondly, Schottky diodes were proposed to be used as high-speed variable impedance loads. A six-port modulator operating at 7.5 GHz, using the carrier leakage suppression technique together with Schottky diodes as variable impedance loads, was manufactured. Measurements on a 16 quadrature amplitude modulated (QAM) signal with a symbol rate of 300 Msymbol/s, i.e., a data rate of 1.2 Gbit/s, have proved high-speed operation, good modulation properties as well as carrier leakage suppression.

    Thirdly, a six-port demodulator was built for high data rate applications and measurements were conducted to characterize its performance. Demodulation of a 16-QAM signal at a data rate of 1.67 Gbit/s results in an acceptable bit error rate and error vector magnitude (EVM) performance.

    Last but not least, new diode configurations were proposed, analyzed and verified for use in six-port demodulators. Using the proposed diode configurations, the use of differential amplifiers, as commonly used in a six-port demodulator, can be avoided. Avoiding the use of differential amplifiers allows high-speed processing and at the same time reduces the power consumption and implementation complexity. In the context of the new diode configurations, it was shown that a six-port receiver has better EVM vs frequency performance and lower implementation complexity, compared to a five-port or four-port receiver.

6061626364 3101 - 3150 of 3161
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