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  • 3051.
    Zandieh, Behdis
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Indoor Wireless Local Area Network (WLAN): Measurement and Modeling from a user perspective2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    If we had detailed wireless local area network (WLAN) coverage maps, both staff and equipment could be used more efficiently, for example, less time would be spent searching for connectivity. In addition, system administrators could understand their WLAN's utilization better, thus enabling better planning for where to install new access points, where to remove access points, where to change the type of antenna, etc. This thesis concerns creating detailed indoor coverage models by using measured network performance - in order to enable both users and administrators to visualize the network coverage. Today a user can only easily know about the access points that they currently hear – in the location where they currently are. Giving the users and administrators access to a model of the entire campus coverage will allow them to understand not only the _local_ coverage, but the patterns of coverage (or lack there of). However, no efficient modeling techniques are currently available for those deploying and operating indoor WLANs.

    The thesis begins with some general background information and then examines a number of WLAN survey tools; in terms of both their performance and cost. Following this a number of related projects are presented. This background provides the motivation for why a new tool is needed and what functions such a tool should have.

    Next a site survey of the KTH campus in Kista was conducted using a newly developed survey application. This application was developed to better meet the requirements derived from the missing functionality of existing tools. In addition, developing this application gave the author an opportunity to learn a new objectoriented programming language, i.e. C# and the .NET environment. Learning to use this new environment was essential to building both an easy to use application and collecting the data from the system - the later was often not straight-forward.

    ne of the key issues after data collection is how to present the collected data to the user and how this varies depending upon the user’s interests and task. An initial representation of the experimental data is presented as a manually painted coverage map overlayed onto a map. Next the thesis examines how to integrate the experimental data using Google’s SketchUp in order to build a 3D model of the WLAN coverage on this campus.

    Future work related to this thesis should focus on how to automate the collection of data and how to automate the presentation of the resulting experimental data.

  • 3052.
    Zapolskas, Vytautas
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Securing Cloud Storage Service2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cloud computing brought flexibility, scalability, and capital cost savings to the IT industry. As more companies turn to cloud solutions, securing cloud based services becomes increasingly important, because for many organizations, the final barrier to adopting cloud computing is whether it is sufficiently secure.

    More users rely on cloud storage as it is mainly because cloud storage is available to be used by multiple devices (e.g. smart phones, tablets, notebooks, etc.) at the same time. These services often offer adequate protection to user's private data. However, there were cases where user's private data was accessible to other users, since this data is stored in a multi-tenant environment. These incidents reduce the trust of cloud storage service providers, hence there is a need to securely migrate data from one cloud storage provider to another.

    This thesis proposes a design of a service for providing Security as a Service for cloud brokers in a federated cloud. This scheme allows customers to securely migrate from one provider to another. To enable the design of this scheme, possible security and privacy risks of a cloud storage service were analysed and identified. Moreover, in order to successfully protect private data, data protection requirements (for data retention, sanitization, and processing) were analysed. The proposed service scheme utilizes various encryption techniques and also includes identity and key management mechanisms, such as "federated identity management".

    While our proposed design meets most of the defined security and privacy requirements, it is still unknown how to properly handle data sanitization, to meet data protection requirements, and provide users data recovery capabilities (backups, versioning, etc.).

  • 3053.
    Zappone, Alessio
    et al.
    TU Dresden, Dresden, Germany.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Sanguinetti, Luca
    University of Pisa, Italy; CentraleSupelec, France.
    Jorswieck, Eduard
    TU Dresden, Dresden, Germany.
    A Framework for Globally Optimal Energy-Efficient Resource Allocation in Wireless Networks2016Conference paper (Refereed)
  • 3054.
    Zdravkovic, Jelena
    et al.
    KTH, School of Information and Communication Technology (ICT), Computer and Systems Sciences, DSV.
    Zikra, Iyad
    KTH, School of Information and Communication Technology (ICT), Computer and Systems Sciences, DSV.
    Ilayperuma, Tharaka
    An MDA method for service modeling by formalizing REA and open-edi business frameworks with SBVR2011In: 4th IFIP WG 8.1 Working Conference on Method Engineering, ME 2011, 2011, 219-224 p.Conference paper (Refereed)
    Abstract [en]

    Business frameworks offer great opportunities of communication between people for working on the enterprise system engineering processes, as well as for eliciting services that the enterprise can offer in collaboration contexts. However, these kinds of frameworks, such as Resource-Event-Agent and Open-edi, recently unified in Open-edi Business Ontology (OeBTO), lack formal representations. This fact considerably limits their use in system development, particularly in model-driven development methods where the efficiency of transformations is of great importance. In this paper we suggest a formalization of OeBTO using OMG's standard Semantics of Business Vocabulary and Business Rules (SBVR), as a method for creating a service-centric business model. This makes it possible to provide the necessary formal logic foundation to allow automatic processing of the business model and its transformation to a system-level service model. An example from the bank loan business sector is used to argument the application of the method.

  • 3055.
    Zeeck, Simon
    KTH, Superseded Departments, Teleinformatics.
    Cellular Interworking: Handover between WATM and GSM1998Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In a wireless environment, it is interesting to roam between different wireless systems, especially if the coverage of one or more of these systems are limited to a certain restricted area, or if there is a cost difference. My work has focused on the support of continuous handover in such a case. The work has focused on Wireless ATM and GSM as bearers for data traffic. The mobile terminal is considered to connect to the GSM or Wireless ATM network. Internet (IP networking) is considered to be the aim of the connection.

    UMTS will probably be the base for new cellular systems. The UMTS core network will most likely be based on ATM. This is what is suggested in the standardization and has support from both Ericsson and Nokia. The WATM is an interesting option for "high speed" wireless network interface that can be connected to UMTS.

    The solution has tried the approch of combining layer 2 tunneling with layer 3 signalling and investigated another solution than network layer mobility.The reasons to investigate this has been:

    • Layer 2 tunneling is a well-know and proven concept in cellular networks
    • The layer 2 connection can be transparently changed while being mobile.
    • Both QoS and traffic parameters in layer2 (e.g., ATM) can be used
    • The freedom and power of IP on layer 3 for signaling (and for data, of course)
  • 3056.
    Zennaro, Marco
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Bagula, Antoine
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Ntareme, Hervé
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Inggs, Gordon
    Scott, Simon
    On the relevance of open wireless sensors for NGN2009In: International Telecommunication Union - Proceedings of the 2009 ITU-T Kaleidoscope Academic Conference: Innovations for Digital Inclusion, K-IDI 2009, IEEE conference proceedings, 2009, 193-200 p.Conference paper (Refereed)
    Abstract [en]

    Open Wireless Sensors are based on the Open Source Software and Open Source Hardware paradigms. The code used to program them and the information about the hardware design are freely released. We present the main characteristics of Open Wireless Sensor Networks (OWSNs) and report on two examples with the experimental results revealing the performance of OWSNs in terms of link quality and battery life. We demonstrate the relevance of using OWSNs in Next Generation Networks by showing the advantages of the Open Source model when applied to Wireless Sensor networks in terms of cost, personalisation and independence from a single entity as compared to proprietary solutions.

  • 3057.
    Zenteno, Efrain
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences. KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Digital Compensation Techniques for Transmitters in Wireless Communications Networks2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Since they appeared, wireless technologies have deeply transformed our society. Today, wireless internet access and other wireless applications demandincreasingly more traffic. However, the continuous traffic increase can be unbearableand requires rethinking and redesigning the wireless technologies inmany different aspects. Aiming to respond to the increasing needs of wirelesstraffic, we are witnessing a rapidly evolving wireless technology scenario.This thesis addresses various aspects of the transmitters used in wireless communications.Transmitters present several hardware (HW) impairments thatcreate distortions, polluting the radio spectrum and decreasing the achievabletraffic in the network. Digital platforms are now flexible, robust and cheapenough to enable compensation of HW impairments at the digital base-bandsignal. This has been coined as ’dirty radio’. Dirty radio is expected in future transmitters where HW impairments may arise to reduce transmitter cost or to enhance power efficiency. This thesis covers the software (SW) compensation schemes of dirty radio developed for wireless transmitters. As describedin the thesis, these schemes can be further enhanced with knowledge of thespecific signal transmission or scenarios, e.g., developing cognitive digital compensationschemes. This can be valuable in today’s rapidly evolving scenarioswhere multiple signals may co-exist, sharing the resources at the same radiofrequency (RF) front-end. In the first part, this thesis focuses on the instrumentation challenges andHWimpairments encountered at the transmitter. A synthetic instrument (SI)that performs network analysis is designed to suit the instrumentation needs.Furthermore, how to perform nonlinear network analysis using the developedinstrument is discussed. Two transmitter HW impairments are studied: themeasurement noise and the load impedance mismatch at the transmitter, asis their coupling with the state-of-the-art digital compensation techniques.These two studied impairments are inherent to measurement systems and areexpected in future wireless transmitters. In the second part, the thesis surveys the area of behavioral modeling and digital compensation techniques for wireless transmitters. Emphasis is placed on low computational complexity techniques. The low complexity is motivated by a predicted increase in the number of transmitters deployed in the network, from base stations (BS), access points and hand-held devices. A modeling methodology is developed that allows modeling transmitters to achieve both reduced computational complexity and low modeling error. Finally, the thesis discusses the emerging architectures of multi-channel transmittersand describes their digital compensation techniques. It revises the MIMOVolterra series formulation to address the general modeling problem anddrafts possible solutions to tackle its dimensionality. In the framework of multi-channel transmitters, a technique to compensate nonlinear multi-carrier satellite transponders is presented. This technique is cognitive because it uses the frequency link planning and the pulse-shaping filters of the individual carriers. This technique shows enhanced compensation ability at reduced computational complexity compared to the state-of-the-art techniques and enables the efficient operation of satellite transponders.

  • 3058.
    Zenteno, Efrain
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Digital Compensation Techniques for Transmitters inWireless Communications Networks2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Since they appeared, wireless technologies have deeply transformed our society. Today, wireless internet access and other wireless applications demandincreasingly more traffic. However, the continuous traffic increase can be unbearableand requires rethinking and redesigning the wireless technologies inmany different aspects. Aiming to respond to the increasing needs of wirelesstraffic, we are witnessing a rapidly evolving wireless technology scenario.This thesis addresses various aspects of the transmitters used in wireless communications.Transmitters present several hardware (HW) impairments thatcreate distortions, polluting the radio spectrum and decreasing the achievabletraffic in the network. Digital platforms are now flexible, robust and cheapenough to enable compensation of HW impairments at the digital base-bandsignal. This has been coined as ’dirty radio’. Dirty radio is expected in future transmitters where HW impairments may arise to reduce transmitter cost or to enhance power efficiency. This thesis covers the software (SW) compensation schemes of dirty radio developed for wireless transmitters. As describedin the thesis, these schemes can be further enhanced with knowledge of thespecific signal transmission or scenarios, e.g., developing cognitive digital compensationschemes. This can be valuable in today’s rapidly evolving scenarioswhere multiple signals may co-exist, sharing the resources at the same radiofrequency (RF) front-end. In the first part, this thesis focuses on the instrumentation challenges andHWimpairments encountered at the transmitter. A synthetic instrument (SI)that performs network analysis is designed to suit the instrumentation needs.Furthermore, how to perform nonlinear network analysis using the developedinstrument is discussed. Two transmitter HW impairments are studied: themeasurement noise and the load impedance mismatch at the transmitter, asis their coupling with the state-of-the-art digital compensation techniques.These two studied impairments are inherent to measurement systems and areexpected in future wireless transmitters. In the second part, the thesis surveys the area of behavioral modeling and digital compensation techniques for wireless transmitters. Emphasis is placed on low computational complexity techniques. The low complexity is motivated by a predicted increase in the number of transmitters deployed in the network, from base stations (BS), access points and hand-held devices. A modeling methodology is developed that allows modeling transmitters to achieve both reduced computational complexity and low modeling error. Finally, the thesis discusses the emerging architectures of multi-channel transmittersand describes their digital compensation techniques. It revises the MIMOVolterra series formulation to address the general modeling problem anddrafts possible solutions to tackle its dimensionality. In the framework of multi-channel transmitters, a technique to compensate nonlinear multi-carrier satellite transponders is presented. This technique is cognitive because it uses the frequency link planning and the pulse-shaping filters of the individual carriers. This technique shows enhanced compensation ability at reduced computational complexity compared to the state-of-the-art techniques and enables the efficient operation of satellite transponders.

  • 3059.
    Zenteno, Efrain
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Amin, Shoaib
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Isaksson, Magnus
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Combating the Dimensionality of Nonlinear MIMOAmplifier Predistortion by Basis Pursuit2014In: Proceedings of the 44th European Microwave Conference, 2014, 833-836 p.Conference paper (Refereed)
    Abstract [en]

    A general description of nonlinear dynamic MIMOsystems, given by Volterra series, has significantly larger complex-ity than SISO systems. Modeling and predistortion of MIMOamplifiers consequently become unfeasible due to the largenumber of basis functions. We have designed digital predistortersfor a MIMO amplifier using a basis pursuit method for reducingmodel complexity. This method reduces the numerical problemsthat appear in MIMO Volterra predistorters due to the largenumber of basis functions. The number of basis functions wasreduced from 1402 to 220 in a 2x2 MIMO amplifier and from127 to 13 in the corresponding SISO case. Reducing the numberof basis functions caused an increase of approximately 1 dB ofmodel error and adjacent channel power ratio.

  • 3060.
    Zenteno, Efrain
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences. ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Amin, Shoaib
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences. ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Händel, Peter
    ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Combating the Dimensionality of Nonlinear MIMO Amplifier Predistortion by Basis Pursuit2014In: Proceedings of the 44th European Microwave Conference, 2014, 833-836 p.Conference paper (Refereed)
    Abstract [en]

    A general description of nonlinear dynamic MIMO systems, given by Volterra series, has significantly larger complexity than SISO systems. Modeling and predistortion of MIMO amplifiers consequently become unfeasible due to the large number of basis functions. We have designed digital predistorters for a MIMO amplifier using a basis pursuit method for reducing model complexity. This method reduces the numerical problems that appear in MIMO Volterra predistorters due to the large number of basis functions. The number of basis functions was reduced from 1402 to 220 in a 2x2 MIMO amplifier and from 127 to 13 in the corresponding SISO case. Reducing the number of basis functions caused an increase of approximately 1 dB of model error and adjacent channel power ratio.

  • 3061.
    Zepernick, Hans-Jürgen
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Iqbal, Muhammad Imran
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Quality of Experience of Digital Multimedia Broadcasting Services: An Experimental Study2016In: 2016 IEEE Sixth International Conference on Communications and Electronics (ICCE), IEEE, 2016, 437-442 p.Conference paper (Refereed)
    Abstract [en]

    Digital multimedia broadcasting (DMB), also know as mobile TV, has been developed as a digital radio transmission technology that supports multimedia services such as TV, radio and datacasting. Especially, the terrestrial version of DMB, referred to as T-DMB, has been widely deployed in South Korea to deliver multimedia services to mobile devices ranging from smartphones to laptops, car navigation systems, and telematic devices for automotives. Although T-DMB is claimed to theoretically work without difficulties in vehicles with speeds up to 300 km/h, in practice, occasional skips and other temporal and spatial artifacts have been observed. In this paper, we provide an experimental study of the Quality of Experience (QoE) of T-DMB with focus on TV services. The study is based on a measurement campaign that was conducted in a live T-DMB system in South Korea consisting of TV broadcasters and DMB receivers in vehicles. In particular, a comprehensive subjective test has been conducted on the DMB test material that was obtained in the measurement campaign. A statistical analysis of the user ratings obtained from the subjective tests is reported to quantify the QoE of T-DMB in terms of mean opinion scores (MOSs) and higher order statistics. The obtained results may be used to develop related QoE models for this type of systems and services. In particular, the results may suggest to exploit insights obtained from higher order statistics such as skewness and kurtosis into QoE modeling rather than considering only MOS and variance.

  • 3062.
    Zerouali, Mehdi
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    VoIP Communications over WLANs: Implementation of a new downlink transmission protocol2010Report (Other academic)
    Abstract [en]

    Voice over IP (VoIP) is becoming more and more popular every day. The number of VoIP service providers is continuously increasing along with the number of customers they serve. Moreover, the latest generation of smartphones and mobile devices now incorporate VoIP support. This enables users within a wireless local area network (WLAN) cell to exchange VoIP traffic with other peers.

    This new traffic potentially poses a problem for WLANs, as the WLAN access point could be required to handle a large number of small packets of encoded speech. Since the access to the media can only be made by one node at a time, all of the devices must contend to access it. If there are multiple calls between nodes in the WLAN and nodes in the fixed network, then all of these packets must go to and from the access point. Moreover the access point needs to transmit the downlink traffic for all of these nodes. Because the Access Point has the same probability of getting access to the media as any other node, this can lead to high delays, and limits the maximum number of simultaneous calls to a rather small number, despite the increasing data rates that the WLAN interfaces are capable of.</p>This project implements and evaluates a new solution that consists of aggregating downlink packets at the access point and transmitting a large multicast packet containing a set of voice frames that need to be sent to nodes within the cell. A demultiplexing process at node extracts the appropriate RTP content from the multicast packet and delivers it locally.

  • 3063.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Comparison of angle-spread in outdoor-to-outdoor and outdoor-to-indoor cases in an urban macro-cesll2005In: Wireless Personal Multimedia Communications (WPMC), Aalborg, Denmark, 2005Conference paper (Refereed)
  • 3064.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Method for Decreasing Fading in a Telecommunication System1998Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The present invention provides a method for decreasing fading and more particularly the down-link fading in a mobile telecommunication system having transmit lobe diversity. The telecommunication system comprises at least one base station having an antenna array providing lobe diversity, and communicating with mobile terminal units. According to the invention, the average path-loss between the base station and a mobile terminal unit is measured by the base station in order to select a set of alternative lobes. The instantaneous down-link path-loss of the alternative lobes between the base station and the mobile terminal unit is also measured by the mobile in order to select a communication lobe from said set of alternative lobes, such that the communication is effected in the communication lobe.

  • 3065. Zetterberg, Per
    Performance of narrow beams in an suburban environment2000In: Vehicular Technology Conferance (VTC 2000-Spring), 2000, 1235-1239 p.Conference paper (Refereed)
  • 3066.
    Zetterberg, Per
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fardi, Ramin
    Open Source SDR Frontend and Measurements for 60-GHz Wireless Experimentation2015In: IEEE Access, E-ISSN 2169-3536, Vol. 3, 445-456 p.Article in journal (Refereed)
    Abstract [en]

    This paper aims to make 60-GHz experimentation possible for a wider range of research groups. We do this by describing a low-cost front-end that can be used in combination with any baseband processing platform. We provide detailed instructions and software for connection with the USRP N200/N210, including general classes for controlling the board and example single-input single-output and 2 x 2 Multiple-Input Multiple Output applications. In addition, we provide measurements to assess the impact of phase noise and other hardware impairments in low-cost millimeter-wave systems for hybrid measurement and simulation studies. Finally, we also perform performance measurements on the hardware. All our materials, such as the hardware design, the software, and the measurements, are freely available.

  • 3067.
    Zetterberg, Per
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jaldén, Niklas
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Investigation of Simple Algorithms for Estimation of Delay-Spread and Angle-Spread2012Report (Other academic)
    Abstract [en]

    In this paper we describe two simple methods for estimation of delay-spread and angle-spread, re-spectively. The algorithms are simple in the sense that the transmitted signal may consist of only threesuperimposed CW tones -and the receiver need only two antennas. The algorithms are also simple in thesense that the computational cost is very low. We verify the algorithms by applying them to wideband andmulti-antenna measurement data, respectively.

  • 3068.
    Zetterberg, Per
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ottersten, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    The Spectrum Efficiency of a Base Station Antenna Array System for Spatially Selective Transmission1995In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 44, no 3, 651-660 p.Article in journal (Refereed)
    Abstract [en]

    In this paper we investigate the spectrum efficiency gain using  ransmittingantenna arrays at the base stations of a mobile cellular  etwork. The proposedsystem estimates the angular positions of the mobiles from the received data, and allows multiple mobiles to be allocated to the same channel within a cell. This is possible by applying a transmit scheme which directs nulls against co-channel users within the cell. It is shown that multiple mobiles per cell is an efficient way of increasing capacity in comparison with reduced channel reuse distance and narrow beams (without directed nulls). The effect of the spatial spread angle of the locally scattered rays in the vicinity of the mobile is also investigated

  • 3069.
    Zhai, Chuanying
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zou, Zhuo
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zheng, Lirong
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Software defined radio IR-UWB positioning platform for RFID and WSN application2012In: Ultra-Wideband (ICUWB), 2012 IEEE International Conference on, IEEE , 2012, 501-505 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a software defined radio (SDR) platform for Impulse Ultra-Wideband (IR-UWB) sensing and positioning applications. The platform is composed by a software simulator (SW) and a hardware testbed (HW). The software simulator based on Matlab offers reconfigurable modules/functions of UWB systems with a graphic user interface (GUI). Correspondingly, the testbed is implemented by an oscilloscope and a set of off-the-shelf components. The oscilloscope (Lecroy WaveMaster 816Zi-A) features high-speed real-time sampling (i.e., 40 GS/s with 16 GHz analog bandwidth) with 4 independent channels, enabling a multi-antenna multichannel receiver network in UWB bands, with signal processing capability at the Nyquist rate. The SW and HW are seamlessly integrated by the build-in software in the oscilloscope. It allows rapid prototypes of various algorithms to be verified in real environments. Finally, a case study on UWB ranging for localization is given to demonstrate the feasibility and usability of the proposed platform.

  • 3070.
    Zhai, Chuanying
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zou, Zhuo
    KTH, School of Information and Communication Technology (ICT), Industrial and Medical Electronics. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zhou, Qin
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Mao, Jia
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Chen, Qiang
    KTH, School of Information and Communication Technology (ICT), Industrial and Medical Electronics. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Tenhunen, Hannu
    KTH, School of Information and Communication Technology (ICT), Industrial and Medical Electronics. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zheng, Lirong
    KTH, School of Information and Communication Technology (ICT), Industrial and Medical Electronics. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Xu, L.
    A 2.4-GHz ISM RF and UWB hybrid RFID real-time locating system for industrial enterprise Internet of Things2016In: Enterprise Information Systems, ISSN 1751-7575, E-ISSN 1751-7583, 1-18 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents a 2.4-GHz radio frequency (RF) and ultra-wide bandwidth (UWB) hybrid real-time locating system (RTLS) for industrial enterprise Internet of Things (IoT). It employs asymmetric wireless link, that is, UWB radio is utilised for accurate positioning up to 10 cm in critical sites, whereas 2.4-GHz RF is used for tag control and coarse positioning in non-critical sites. The specified communication protocol and the adaptive tag synchronisation rate ensure reliable and deterministic access with a scalable system capacity and avoid unpredictable latency and additional energy consumption of retransmissions due to collisions. The tag, consisting of a commercial 2.4-GHz transceiver and a customised application-specific integrated circuit (ASIC) UWB transmitter (Tx), is able to achieve up to 3 years’ battery life at 1600 tags per position update second with 1000 mAh battery in one cluster. The time difference of arrival (TDoA)–based positioning experiment at UWB radio is performed on the designed software-defined radio (SDR) platform.

  • 3071.
    Zhai, Chuanying
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zou, Zhuo
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zhou, Qin
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zheng, Lirong
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    A Software Defined Radio platform for passive UWB-RFID localization2012In: 2012 IEEE International Conference on Wireless Information Technology and Systems, ICWITS 2012, IEEE , 2012, 6417741- p.Conference paper (Refereed)
    Abstract [en]

    Radio-Frequency-Identification (RFID) with high sensing and positioning capability is the key technology enabler for the vision of the context-aware and location-aware computing towards the Internet-of-Things. However, the existing passive RFID in Ultra-High-Frequency (UHF) based on backscattering scheme can only provide limited ranging resolution and insufficient localization accuracy. Besides, it is sensitive to narrowband interference and multipath environment. Alternatively, Ultra-Wideband (UWB) has been recognized as a promising technology for the next generation RFIDs [1,2]. The Impulse-radio UWB (IR-UWB) implementations employ sub-nanosecond duration pulses without carrier, thus significantly reducing hardware complexity and power consumption. The wideband of the signals provide the potential of fine resolution in dense multipath scenarios. As one of the most attractive characteristics, UWB RFID potentially provides centimeter-level localization accuracy thanks to the ultrashort pulses with high time domain resolution by using time-of-arrival (ToA) estimation of the signal. There has been many works using UWB as active RFID tags for positioning and tracking application [3,4]. Moreover, in order to introduce UWB to passive RFID systems, UHF powered UWB-RFID system with asymmetric links has been proposed in [5]. Based on this UHF/UWB hybrid architecture, the positioning feasibility and ToA estimation has been studied in [6] in algorithm level.

  • 3072.
    Zhang, Congcong
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    A Distributed Range Query Framework for Internet of Things2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the rapid development of information technology, applications referring to the Internet of things are booming. Applications that gather information from sensors and affect the context environment with actuators can provide customized and intelligent behaviour to users. These applications have become widely used nowadays in daily life and have initiated the multi-dimensional range query demand referring to the Internet of things. As the data information is fully distributed and the devices like sensors, mobile phones, etc., has limited resources and finite energy, supporting efficient range query is a tough challenge. In this paper, we have proposed a distributed range query framework for Internet of things. In order to save energy costs and reduce the network traffic, we suggest a reporting data range mechanism in the sensing peers, which choose to report a data range and report again only when the peer senses an abnormal data instead of the common moving data method. In addition, we selected some strong peers to be used as the super peers to create a data index by collecting the reporting data range, which will be used for performing range queries. The study has shown that our proposal framework could reduce resource costs in the less strong peers like sensors and mobile phones, and reduce network traffic among all the peers within the network, as well as support a range query function. According the evaluation results, the reporting data range method could greatly reduce the data migration times and save energy costs, and the data index could significantly reduce accessing unnecessary peers and diminish the network traffic.

  • 3073.
    Zhang, Feng
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture.
    Secure Mobile Service-Oriented Architecture2012Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Mobile transactions have been in development for around ten years. More and more initiatives and efforts are invested in this area resulting in dramatic and rapid development and deployment of mobile technologies and applications. However, there are still many issues that hinder wider deployment and acceptance of mobile systems, especially those handling serious and sensitive mobile transactions. One of the most important of them is security.This dissertation is focused on security architecture for mobile environments. Research issues addressed in this dissertation are based on three currently important groups of problems: a) lack of an open, comprehensive, adaptable and secure infrastructure for mobile services and applications; b) lack of standardized solutions for secure mobile transactions, compliant with various regulatory and user requirements and applicable to different types of popular mobile devices and hardware/software mobile platforms; and c) resource limitations of mobile devices and mobile networks.The main contribution of this dissertation is large-scale, secure service-oriented architecture for mobile environments. The architecture structures secure mobile transaction systems into seven layers, called trusted stack, which is equivalent to ISO/OSI layered networking model. These layers are, starting from the bottom: 1) secure element (chip) layer, 2) applets layer, 3) middleware layer, 4) mobile applications layer, 5) communication layer, 6) services broker layer, and 7) mobile service provider layer. These seven layers include all necessary components required for implementation and operations of secure mobile transaction systems and therefore provide a framework for designing and implementing such systems.Besides the architecture, four types of security services necessary and critical for serious mobile transactions, have also been designed and described in the dissertation. These services are: (1) mobile registration and identity management; (2) mobile PKI; (3) mobile authentication and authorization; and (4) secure messaging. These services are lightweight, therefore suitable for mobile environments, technologies and applications, and also compliant with existing Internet security standards.Finally, as the proof of correctness of the proposed concept and methodology, a prototype system was also developed based on the designed security architecture. The system provides comprehensive security services mentioned above to several types of mobile services providers: mobile banking, mobile commerce, mobile ticketing, and mobile parking. These types of providers have been selected only as currently the most popular and representative, since the architecture is applicable to any other type of mobile service providers.

  • 3074.
    Zhang, Feng
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Kondoro, Aron
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Muftic, Sead
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Location-based authentication and authorization using smart phones2012In: Proc. of the 11th IEEE Int. Conference on Trust, Security and Privacy in Computing and Communications, TrustCom-2012 - 11th IEEE Int. Conference on Ubiquitous Computing and Communications, IUCC-2012, IEEE , 2012, 1285-1292 p.Conference paper (Refereed)
    Abstract [en]

    Authentication and authorization are two of the most important security features for mobile transaction systems. Most commonly, these schemes depend on three factors: what you know (secret), what you have (token), and what you are (biometrics). In this paper, we propose a location-based authentication and authorization scheme for mobile transactions using smart phones. The paper first describes the distinguished features and the architecture of our proposed solution. Second, the core of our design, including three parts: location registration, authentication and authorization as well as location verification, are described.

  • 3075.
    Zhang, Feng
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Kounelis, Ioannis
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Muftic, Sead
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Generic, secure and modular (GSM) methodology for design and implementation of secure mobile applications2012In: SECURWARE 2012 - 6th International Conference on Emerging Security Information, Systems and Technologies, Rome, Italy: International Academy, Research and Industry Association (IARIA), 2012, 1-6 p.Conference paper (Refereed)
    Abstract [en]

    The generic, secure and modular methodology, described in this paper, provides a generic approach for the design and development of secure mobile applications. It is applicable to multiple mobile phone platforms and mobile operating environments. This approach treats a mobile application in a holistic way and structures it into four groups of modules: user interface modules, communication modules, security modules, and business logic modules. These four groups of modules can be designed and implemented independently and finally be integrated together. This approach not only simplifies the process of design and development of mobile applications, but also improves the reusability and robustness of mobile applications. In addition, this paper proposes a trusted layer model for designing the security modules of mobile applications, which provides generic application interfaces and comprehensive data protection. The paper finally gives an example of a secure mobile application, called SAFE Mobile Wallet, which was designed and implemented using GSM methodology.

  • 3076.
    Zhang, Feng
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Muftic, Sead
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Schmöelzer, Gernot
    Secure Service-Oriented Architecture for Mobile Transactions2011In: World Congress on Internet Security (WorldCIS-2011), London: IEEE Communications Society, 2011, 133-138 p.Conference paper (Refereed)
    Abstract [en]

    The paper describes secure service-oriented architecture for mobile transactions. The architecture comprises components, protocols, applications and interfaces and it provides various security services to various mobile applications: registration, certification, authentication, and authorization of users, secure messaging at an application–level (end–to–end security), protection of data in databases, and security services for protection of its own components. The architecture is modular, integrated, extendible and scalable. The paper describes design of the architecture, the status of its current implementation, and future research and development plans.

  • 3077. Zhang, Haibo
    et al.
    Österlind, Fredrik
    Soldati, Pablo
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Johansson, Mikael
    Time-optimal convergecast with separated packet copying: Scheduling policies and performance2015In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 64, no 2, 793-803 p.Article in journal (Refereed)
    Abstract [en]

    Convergecast, in which packets originating from multiple sources are reported to a single sink, is a fundamental primitive for data collection in wireless sensor networks. This paper investigates the time-optimal link-scheduling problem for time-division multiple-access (TDMA)-based convergecast, aiming to minimize the amount of time required to complete convergecast. We observe that packet copying between the microcontroller and the radio transceiver in existing sensor platforms has a big impact on the packet forwarding delay, and we propose a novel model for convergecast in which packet copying is separated from packet transmission and reception. We establish tight lower bounds on the number of time slots required for convergecast in networks with line and tree routing topologies, and we present both centralized and distributed algorithms for constructing the time-optimal convergecast schedules. We evaluate our scheme in both simulations and experiments on hardware. The results show that our scheme can achieve a system throughput (defined as the number of data bits received by the sink per second) of 202.8 kb/s, which is 86.31% of the theoretical bound. In comparison with the traditional TDMA-based convergecast schemes, our scheme can achieve up to a 86.22% improvement on system throughput.

  • 3078.
    Zhang, Hao
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    A Peer to Peer Security Protocol for the Internet of Things: Secure Communication for the SensibleThings Platform2014Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the rapid development of the Internet connected technologies and applications, people are keen on embracing the convenience and practi-­‐‑ calities they brings. As all kinds of technologies improve, the Internet of Things matures and is able to provide more advanced services to people, which connects a variety of devices, systems and applications beyond traditional machine-­‐‑to-­‐‑machine. However, it covers a variety of devices, protocols and applications, which makes it much more complex than a normal network. Nevertheless, equipped with appropriate security solutions, the Internet of Things is promising to bring us more conven-­‐‑ iences and be widely applied in our daily life. And like the main appli-­‐‑ cation areas, wireless sensor networks with a frequent but short com-­‐‑ munication character, it requires an efficient and flexible protocol to protect the information. To protect the traffic of the Internet of Things is the focal point of this research work. Although many protocols for the Internet have been put forward, it is still not enough to meet the increas-­‐‑ ingly complex requirements from applications. Many of them are not efficient enough to adapt the device diversity and timely communica-­‐‑ tion environment. This research work is trying to address this problem, by proposing a peer-­‐‑to-­‐‑peer security protocol to satisfy this varied environment. Secure communication is implemented on an open sourced platform for the Internet of Things. The philosophy of the platform it implemented on is also inherited to this protocol and the implementation. It avoids unnecessary handshakes between entities, which makes it more efficient in a wireless sensor network. Modulariza-­‐‑ tion and unit test are adapted in implementation to enhance the robust of the system. Its dynamic security level adjustment feature satisfies the realistic demand on one platform this protocol is implemented on. Finally, with a comparison test and an analysis using the BAN logic, the result shows that the proposed protocol is efficient to meet the specific goals and applicable for the platform. 

  • 3079.
    Zhang, Hengchong
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Non-binary Authentication: Supplicant2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There are a number of authentication methods for wireless local area networks. The IEEE 802.1x standard is one such method. This standard specifies a port-based access control protocol. There are three entities involved: a supplicant (a device that wishes to have network access and perhaps other services), an Access Point (AP) or other port to which access is to be controlled, and an Authentication Server (AS). The goal of this project was to design, implement, and evaluate a prototype of a non-binary alternative to IEEE 802.1x authentication. This report focuses on the supplicant. Specifically it describes the design, implementation, and evaluation of a supplicant program to test and stress the authenticator, in order to evaluate a non-binary authentication process.

    Following, a brief introduction is given to the problem that is to be solved, a number of existing IEEE 802.1x supplicants are described and compared. Following this, a number of potential non-binary authentication processes are analyzed. The ability of a supplicant to send and receive packets before and after authentication is also examined. Based upon our implementation and evaluation of a supplicant and an emulation of the non-binary authentication process, we conclude that non-binary authentication is both feasible and valuable. Furthermore, the thesis evaluates why and how non-binary authentication is valuable from the viewpoint of a supplicant. Additional future work is suggested at the end of this thesis.

  • 3080.
    Zhang, Ke
    et al.
    University of Electronic Science and Technology of China, Chengdu, China.
    Mao, Yuming
    University of Electronic Science and Technology of China, Chengdu, China.
    Leng, Supeng
    University of Electronic Science and Technology of China, Chengdu, China.
    Maharjan, Sabita
    Simula Research Laboratory, Oslo, Norway.
    Zhang, Yan
    Simula Research Laboratory, Oslo, Norway.
    Vinel, Alexey
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Jonsson, Magnus
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Incentive-Driven Energy Trading in the Smart Grid2016In: IEEE Access, E-ISSN 2169-3536, Vol. 4, 1243-1257 p., 7436757Article in journal (Refereed)
    Abstract [en]

    The smart grid is widely considered as an efficient and intelligent power system. With the aid of communication technologies, the smart grid can enhance the efficiency and reliability of the grid system through intelligent energy management. However, with the development of new energy sources, storage and transmission technologies together with the heterogeneous architecture of the grid network, several new features have been incorporated into the smart grid. These features make the energy trading more complex and pose a significant challenge on designing efficient trading schemes. Based on this motivation, in this paper, we present a comprehensive review of several typical economic incentive approaches adopted in the energy-trading control mechanisms. We focus on the technologies that address the challenges specific to the new features of the smart grid. Furthermore, we investigate the energy trading in a new cloud-based vehicle-to-vehicle energy exchange scenario. We propose an optimal contract-based electricity trading scheme, which efficiently increases the generated profit. © 2013 IEEE.

  • 3081.
    Zhang, Ke
    et al.
    School of Communication and Information Engineering, University of Electronic Science and Technology of China, Chengdu, China.
    Mao, Yuming
    School of Communication and Information Engineering, University of Electronic Science and Technology of China, Chengdu, China.
    Leng, Supeng
    School of Communication and Information Engineering, University of Electronic Science and Technology of China, Chengdu, China.
    Vinel, Alexey
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Zhang, Yan
    Simula Research Laboratory, Oslo, Norway.
    Delay constrained offloading for Mobile Edge Computing in cloud-enabled vehicular networks2016In: Proceedings of 2016 8th International Workshop on Resilient Networks Design and Modeling (RNDM) / [ed] Magnus Jonsson, Jacek Rak, Arun Somani, Dimitri Papadimitriou & Alexey Vinel, Piscataway: IEEE Press, 2016, 288-294 p.Conference paper (Refereed)
    Abstract [en]

    Cloud-based vehicular networks is a new paradigm to improve the vehicular services through distributing computation tasks between remote clouds and local vehicular terminals. To further reduce the latency and the transmission cost of the computation offloading, we propose a cloud-based Mobile Edge Computing (MEC) offloading framework in vehicular networks. In the framework, efficient computation offloading strategies are designed through a contract theoretic approach. We obtain the optimal feasible contracts that maximize the benefit of the MEC service provider while enhancing the utilities of the vehicles. Furthermore, considering the resource limitation of the MEC server and the latency tolerance of the computation tasks, we propose a contract-based computation resource allocation scheme. Numerical results show that our proposed scheme greatly enhances the utility of the MEC service provider. ©2016 IEEE 

  • 3082.
    Zhang, Ke
    et al.
    School of Communication and Information Engineering, University of Electronic Science and Technology of China, Chengdu, Kina.
    Mao, Yuming
    School of Communication and Information Engineering, University of Electronic Science and Technology of China, Chengdu, Kina.
    Leng, Supeng
    School of Communication and Information Engineering, University of Electronic Science and Technology of China, Chengdu, Kina.
    Zeng, Ming
    School of Communication and Information Engineering, University of Electronic Science and Technology of China, Chengdu, Kina.
    Xu, Liang
    School of Communication and Information Engineering, University of Electronic Science and Technology of China, Chengdu, Kina.
    Jiang, Li
    Beijing University of Posts and Telecommunications, Beijing, China.
    Vinel, Alexey
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Optimal energy exchange schemes in smart grid networks: A contract theoretic approach2016In: 2016 IEEE/CIC International Conference on Communications in China (ICCC), Piscataway: IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    Vehicle-to-Grid (V2G) is a promising paradigm to alleviate energy supply and demand imbalance of the grid. To further improve the power transmission efficiency, in this paper, we propose a cloudlet-based Vehicle-to-Vehicle (V2V) energy exchange framework. In the framework, the Energy Switch Center (ESC) serves as a trading broker, which purchases electricity from discharging vehicles and then resells it to the charging ones without energy transmission on the grid. The energy trading process is modeled in a contract theoretic approach. We derive the optimal feasible contracts which maximize the profit of the ESC. Furthermore, we systematically study the practical scenario where both the charging demand and renewable energy supplement are random variables, and propose a practical optimal contract-based electricity purchase scheme. Simulation results show that the proposed scheme can efficiently increase the profit of the ESC than the other mechanisms. © 2016 IEEE.

  • 3083. Zhang, L.
    et al.
    Wang, T.
    Liu, Q.
    Hu, X.
    Wang, Jing
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Su, Y.
    Increasing the delay-bit rate product on silicon chip using Star-16QAM signal with high spectral efficiency2009In: Optical Transmission Systems, Switching, and Subsystems VII, 2009, 763204- p.Conference paper (Refereed)
    Abstract [en]

    We proposed and experimentally demonstrate the generation of a novel star-16QAM using a dual-parallel Mach-Zehnder modulator (DPMZM) followed by a phase modulator (PM). Coherent detection and off-line processing are used to recover constellation diagrams. We also study optical delay of a novel star-16QAM signal through a silicon microring resonator. Delay time of ∼ 30ps is observed by comparing the eye diagram of the star-16QAM signal on-resonance with that off-resonance.

  • 3084. Zhang, L.
    et al.
    Wang, T.
    Liu, Q.
    Hu, X.
    Wang, Jing
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Su, Y.
    Increasing the delay-bit rate product on silicon chip using star-16QAM signal with high spectral efficiency2009In: 2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009, 2009Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrate optical delay of a novel star-16QAM signal through a silicon microring resonator. Delay time of ∼ 30ps is observed by comparing the eye diagram of the star-16QAM signal on-resonance with that off-resonance.

  • 3085. Zhang, Lei
    et al.
    Fu, Di
    Liu, Jiangchuan
    Ngai, Edith C.-H.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Zhu, Wenwu
    On energy-efficient offloading in mobile cloud for realtime video applications2017In: IEEE transactions on circuits and systems for video technology (Print), ISSN 1051-8215, E-ISSN 1558-2205, Vol. 27, no 1, 170-181 p.Article in journal (Refereed)
    Abstract [en]

    Batteries of modern mobile devices remain severely limited in capacity, which makes energy consumption a key concern for mobile applications, particularly for the computation-intensive video applications. Mobile devices can save energy by offloading computation tasks to the cloud, yet the energy gain must exceed the additional communication cost for cloud migration to be beneficial. The situation is further complicated by real-time video applications that have stringent delay and bandwidth constraints. In this paper, we closely examine the performance and energy efficiency of representative mobile cloud applications under dynamic wireless network channels and state-of-the-art mobile platforms. We identify the unique challenges of and opportunities for offloading real-time video applications and develop a generic model for energy-efficient computation offloading accordingly in this context. We propose a scheduling algorithm that makes adaptive offloading decisions in fine granularity in dynamic wireless network conditions and verify its effectiveness through trace-driven simulations. We further present case studies with advanced mobile platforms and practical applications to demonstrate the superiority of our solution and the substantial gain of our approach over baseline approaches.

  • 3086. Zhang, Lin
    et al.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Wu, Gang
    Zhao, Guodong
    Liang, Ying-Chang
    Li, Shaoqian
    Proactive Cross-Channel Gain Estimation for Spectrum Sharing in Cognitive Radio2016In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 34, no 10, 2776-2790 p.Article in journal (Refereed)
    Abstract [en]

    In an underlay cognitive radio network, the cross-channel gain from a cognitive transmitter (CT) to a primary receiver (PR) is crucial for spectrum sharing. By exploiting the relaying capability of the CT, we propose a proactive estimation scheme for the cross-channel gain. Specifically, the CT proactively acts as a full-duplex amplify-and-forward (AF) relay for primary transceivers to trigger the power adaption of a primary transmitter (PT). By carefully designing the relay signal, the CT is able to obtain an estimation of the cross-channel gain by observing the power adaption. To demonstrate the accuracy of the estimation, we analytically characterize both an upper bound and a lower bound of the estimation performance. Furthermore, we study the impact of CT's relaying on the primary transmission and observe that the impact is related to the CT's location. By introducing a factor phi (0 <= phi <= 1) to denote the probability that the CT's relaying improves the primary transmission instead of causes interference, we design the CT location as a function of f. Numerical results show that the estimation error of the proactive estimation scheme can be as small as 1.7% with success estimation probability around 91%. By comparing with the state of the art, we show the advantages of the proposed estimator.

  • 3087.
    Zhang, P.
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Costa, J.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Tekeusso, Boris
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Wahlstrand, N.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Carmona, O.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    M2M Communications in LTE SystemsIn: Wireless networks, ISSN 1022-0038, E-ISSN 1572-8196Article in journal (Other academic)
    Abstract [en]

    In wide-area applications, low-cost and massive machine to machine (M2M) communications provided bycellular networks will be one main driver for the success of future Internet of Things (IoT) development. The first directconsequence of the proliferation of IoT is that large numbers of devices will produce huge quantities of sporadic data andsignificantly higher capacity of cellular networks will be needed - not in terms of megabits transported, but the numberof machines sustained. In this paper, we will investigate the support of M2M communications in LTE systems. The goalof this paper is to survey how the existing LTE architecture supports M2M traffic in terms of capacity, coverage, andsignaling, assuming a certain usage scenario and traffic pattern. Solutions are suggested for issues that arise whena large amount of M2M traffic is transported over an LTE network. We will show that the capacity and coverage arenot the key issues; instead the signaling is the main bottleneck, especially the ones related to the RACH. Finally, as atypical illustrating example, we will study in detail how Smart Metering application can be supported in LTE systems andinvestigate thoroughly solutions to the key bottlenecks in this paper.

  • 3088.
    Zhang, Peng
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Energy-Efficient Clustering Design for M2M Communications2014In: 2014 IEEE Global Conference on Signal and Information Processing (GlobalSIP), 2014Conference paper (Refereed)
    Abstract [en]

    Machine-to-machine (M2M) communications in cellular networks enables Internet of Things in the macro geographical regions and is a promising technique in next-generation wireless networks. In this paper, we study energy-efficient clusteringdesign in cellular networks to maximize the overall network battery life time.

    We propose a new clustering design which finds the optimal number of clusters in a cellular network, and maximizes the network energy efficiency, meanwhile rulesof selecting and rotating cluster heads. Different from existing clustering designs, we consider both transmission and circuit energy consumption in this paper. The network performance will be both rigorously analyzed and evaluated using simulations withrespect to dead device ratio, residual energy, and network life. The simulation results show that by using the proposed clustering approach, the network battery life can be improved significantly.

  • 3089.
    Zhang, Shasha
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Device aggregation with data networking: Implementing a Personal Area Network2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Technology is advancing rapidly and intelligent devices are becoming affordable and wireless infrastructure is becoming pervasive. Personal information technology appliances have become part of our life, via cellular phones, PDAs, Bluetooth headsets, handheld keyboards, GPS, and digital cameras. In the future, new intelligent devices will be invented as technology evolves. However, because multiple devices provide similar (but different) functionality it is complex for the average user to choose a single device. Moreover, today it is hard to configure, administer, and use several different appliances together. In order to be utilized in an effective manner and in an accessible way, personal devices should be aggregated, i.e., connected together via a local area network so that they can appear to the user as if they were a single device.

    This paper introduces a connection model based on device aggregation to realize shared state, the behavior of a shared appliance, and with the superset of the individual device functionality. Such an aggregated logical device might even exhibit functions which a user would have a very hard time realizing by manually combining devices. This will facilitate the user’s control over their appliances (build of different devices), but acting as one device.

    The project was a joint effort with David Sabaté Mogica. We developed such a system based on Dynamic Host Client protocol (DHCP) and Service Location Protocol (SLP) for service discovery and Virtual Network Computing (VNC) for remote desktop control. The system builds on a laboratory network environment. This thesis concerns the implementation and evaluation of service discovery. The Remote desktop control was researched and implemented separately and will be reported separately. Service discovery between two computers has been implemented using a custom program developed for a PDA. However, at present the PDA only sends a DA request packet with DHCP. However, service discovery has been successfully tested between two computers. This provided an important base for the programming on PDA and the future development of a similar program for a cellular phone.

  • 3090.
    Zhang, Xi
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Palomar, Daniel P.
    Dept. of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Robust design of linear MIMO transceivers under channel uncertainty2006In: 2006 IEEE International Conference on Acoustics, Speech, and Signal Processing: signal processing for communication, sensor array and multichannel signal processing, 2006, 77-80 p.Conference paper (Refereed)
    Abstract [en]

    This paper considers the robust design of a linear transceiver with imperfect channel state information (CSI) at the transmitter of a MIMO link. The framework embraces the design problem when CSI at the transmitter consists of the channel mean and covariance matrix or, equivalently, the channel estimate and the estimation error covariance matrix. The design of the linear MIMO transceiver is based on a general cost function covering several well known performance criteria. In particular, two families are considered in detail: Schur-convex and Schur-concave functions. Approximations are used in the low SNR and high SNR regimes separately to obtain simple optimization problems that can be readily solved. Numerical examples show gains compared to other suboptimal methods.

  • 3091.
    Zhang, Xi
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Palomar, Daniel P.
    Electrical Engineering, Princeton University, Princeton.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Statistically robust design of linear MIMO transceivers2008In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 56, no 8, 3678-3689 p.Article in journal (Refereed)
    Abstract [en]

    The treatment of channel state information (CSI) is critical in the design of MIMO systems. Accurate CSI at the transmitter is often not possible or may require high feedback rates. Herein, we consider the robust design of linear MIMO transceivers with perfect CSI either at the transmitter or at both sides of the link. The framework considers the design problem where the imperfect CSI consists of the channel mean and covariance matrix or, equivalently, the channel estimate and the estimation error covariance matrix. The robust transceiver design is based on a general cost function of the average MSEs as well as a design with individual MSE based constraints. In particular, a lower bound of the average MSE matrix is explored for the design when only the CSI at the transmitter is imperfect. Under different CSI conditions, the proposed robust transceivers exhibit a similar structure to the transceiver designs for perfect CSI, but with a different equivalent channel and/or noise covariance matrix.

  • 3092. Zhang, Xu
    et al.
    Othman, Maisara B
    Pang, Xiaodan
    RISE ACREO AB; Technical University of Denmark.
    Jensen, Jesper B
    Monroy, Idelfonso Tafur
    Bi-directional multi dimension CAP transmission for smart grid communication services2012In: Communications and Photonics Conference (ACP), 2012 Asia, Optical Society of America, 2012, 1-3 p.Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrate bi-directional multi dimension carrierless amplitude and phase (CAP) transmission for smart grid communication services based on optical fiber networks. The proposed system is able to support multi-Gb/s transmission with high spectral efficiency.

  • 3093. Zhang, Xu
    et al.
    Pang, Xiaodan
    Technical University of Denmark, Denmark.
    Deng, Lei
    Zibar, Darko
    Monroy, Idelfonso Tafur
    Younce, Richard
    High phase noise tolerant pilot-tone-aided DP-QPSK optical communication systems2012In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 18, 19990-19995 p.Article in journal (Refereed)
    Abstract [en]

    In this paper we experimentally demonstrate a novel, high phase-noise tolerant, optical dual polarization (DP) quadrature phase-shift keying (QPSK) communication system based on pilot-tone-aided phase noise cancellation (PNC) algorithm. Vertical cavity surface emitting lasers (VCSELs) with approximate 300 MHz linewidth are used as transmitters and local oscillators for coherent detection of optical DP-QPSK signals. The proposed system, with central wavelength at 1540.68 nm, operates at 40 Gb/s over 80 km single mode fiber (SMF) as part of a passive optical network (PON). The deployment of pilot-tone-aided PNC algorithm guarantees a bit error rate (BER) performance below the forward error correction (FEC) threshold. Moreover, we also evaluate a novel digital signal processing (DSP) algorithm for adaptive pilot tone detection.

  • 3094. Zhang, Xu
    et al.
    Pang, Xiaodan
    RISE ACREO AB; Technical University of Denmark.
    Dogadaev, Anton K
    Monroy, Idelfonso Tafur
    Zibar, Darko
    Younce, Richard C
    High spectrum narrowing tolerant 112 Gb/s dual polarization QPSK optical communication systems using digital adaptive channel estimation2012In: 2012 Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference, OFC/NFOEC 2012, 2012Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrate high spectrum narrowing tolerant 112-Gb/s QPSK polarization multiplex system based on digital adaptive channel estimation method. The proposed algorithm is able to detect severe spectrum-narrowed signal even with 20GHz 3dB bandwidth.

  • 3095.
    Zhang, Yan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wireless sensor network for volcano monitoring2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The monitoring of volcanoes for risk assessment has deployed single sensors for years. This kind of system requires manual supervision to monitor each sensor, which makes the monitoring work not flexible and efficient enough to adapt to variable volcano environments. With the development of wireless sensor networks, the accuracy and coverage of volcano observations can be improved by deploying networked sensors. This paper proposes a wireless sensor network prototype for volcano remote monitoring, which was built and tested in a field campaign in volcano Etna, Italy in September of 2004.Hardware design of sensors, in-depth sensor network design and software module architecture will be introduced in this paper. The experience gained from the practical work in volcano Etna will be used in an upcoming volcano monitoring project.

  • 3096.
    Zhang, Yuanhui
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Evaluating a publish/subscribe proxy for HTTP2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the increasingly high speed of the Internet and its wide spread usage, the current Internet architecture exhibits some problems. The publish/subscribe paradigm has been developed to support one of the most common patterns of communication. It makes “information” the center of communication and removes the “location-identity split” (i.e., that objects are at specific locations to which you must communicate with to access the object). In this thesis project a publish/subscribe network is built and then used in the design, implementation, and evaluation of a publish/subscribe proxy for today’s HTTP based communication. By using this proxy users are able to use their existing web browser to send both HTTP requests and Publish/Subscribe Internet Routing Paradigm (PSIRP) requests. A publish/subscribe overlay is responsible for maintaining PSIRP contents. The proxy enables web browser clients to benefit from the publish/subscribe network, without requiring them to change their behavior or even be aware of the fact that the content that they want to access is being provided via the publish/subscribe overlay. The use of the overlay enables a user’s request to be satisfied by any copy of the content, potentially decreasing latency, reducing backbone network traffic, and reducing the load on the original content server. One of the aims of this thesis is to make more PSIRP content available, this is done by introducing a proxy who handles both HTTP and PSIRP requests, but having received content as a result of an HTTP response it publishes this data as PSIRP accessible content. The purpose is to foster the introduction and spread of content based access.

  • 3097. Zhang, Zhengquan
    et al.
    Ma, Zheng
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Information Science and Engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ding, Zhiguo
    Fan, Pingzhi
    Full-Duplex Device-to-Device-Aided Cooperative Nonorthogonal Multiple Access2017In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 66, no 5, 4467-4471 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents a full-duplex device-to-device (D2D)-aided cooperative nonorthogonal multiple access (NOMA) scheme to improve the outage performance of the NOMA-weak user in a NOMA user pair, where the NOMA-weak user is helped by the NOMA-strong user with the capability of full-duplex D2D communications. The expressions for the outage probability are derived to characterize the performance of the proposed scheme. The results show that the proposed cooperative NOMA scheme can achieve superior outage performance compared to the conventional NOMA and orthogonal multiple access (OMA). In order to further improve the outage performance, an adaptive multiple access (AMA) scheme is also studied, which dynamically switches between the proposed cooperative NOMA, conventional NOMA, and OMA schemes, according to the level of residual self-interference and the quality of links. The results show that the AMAscheme outperforms the above multiple access schemes in terms of outage performance.

  • 3098.
    Zhang, Zhi
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Lu, Zhonghai
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Chen, Qiang
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Yan, Xiaolang
    Zheng, Li-Rong
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Code division multiple access/pulse position modulation ultra-wideband radio frequency identification for Internet of Things: concept and analysis2012In: International Journal of Communication Systems, ISSN 1074-5351, E-ISSN 1099-1131, Vol. 25, no 9, 1103-1121 p.Article in journal (Refereed)
    Abstract [en]

    Radio frequency identification (RFID) is a compelling technology for Internet of Things (IoT). Ultra-wideband (UWB) technology is one promising wireless technique for future RFID, especially for high-throughput sensing applications. On-off keying UWB RFID system provides high pulse rate but suffers severe collisions that limit the system throughput. This paper proposes to utilize low pulse rate code division multiple access/pulse position modulation UWB in the tag-to-reader link to provide multiple tag access capability and build a high-throughput RFID system for IoT. We analyze asynchronous matched filter receiver and decorrelating receiver for multi-tag detection and design an effective medium access control scheme to optimize the network throughput. We propose an effective dynamic frame size adjustment algorithm on the basis of theoretical analysis and determine the preferable length of Gold codes. With a similar data rate, the throughput of the proposed system using the decorrelating receiver is 8.6 times higher than that of the electronic product code class 1 generation 2 system. Only using 1/10 pulse rate and 1/15 data rate, the proposed system outperforms the on-off keying UWB RFID system 1.4 times in terms of throughput.

  • 3099.
    Zhao, Hao
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Secure Management of Multi-Application Mobile Platforms2014Doctoral thesis, monograph (Other academic)
  • 3100.
    Zhao, Hao
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Muftic, Sead
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    The concept of secure mobile wallet2011In: World Congress on Internet Security, WorldCIS-2011, 2011, 54-58 p.Conference paper (Refereed)
    Abstract [en]

    This paper describes our concept, design and current implementation of the Secure Mobile Wallet. Mobile Wallet is an application stored in mobile phones providing to subscribers the possibility to perform various mobile financial transactions. In our approach Secure Mobile Wallet is stored and running in the Javacard SIM chip, called UICC. It comprises several Javacard applets supporting several types of financial transactions - mobile banking, mobile payments, mobile commerce, mobile micro-loans, mobile ticketing, mobile promotions, and so on. Secure Mobile Wallet supports over-the-air (OTA) transactions based on SMS, GPRS, or mobile Internet protocols and also over-the-counter (OTC) transactions based on NFC or Bluetooth protocols. For users, messages and data stored in the Secure Mobile Wallet are managed and maintained using both, OTA and OTC, protocols. Security is guaranteed by a combination of symmetric and asymmetric cryptography. As a client's application, the Secure Mobile Wallet is integrated into our larger, secure mobile transactions system - SAFE™.

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