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  • 2251.
    Zhang, Lu
    et al.
    KTH, School of Information and Communication Technology (ICT). Shanghai Jiao Tong University, Shanghai, China.
    Pang, Xiaodan
    KTH, School of Information and Communication Technology (ICT). RISE Acreo AB, Kista, Sweden.
    Ozolins, O.
    Udalcovs, A.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT).
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT).
    Jacobsen, G.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT).
    Xiao, S.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT).
    15-Gbaud PAM4 Digital Mobile Fronthaul with Enhanced Differential Pulse Coding Modulation Supporting 122 LTE-A Channels with up to 4096QAM2018In: 2017 European Conference on Optical Communication (ECOC), Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 1-3Conference paper (Refereed)
    Abstract [en]

    By employing enhanced DPCM, 15-Gbaud PAM4 digital mobile fronthaul is experimentally demonstrated to support 122 LTE-A channels with up to 4096QAM. Compared to PCM based CPRI, the supported number of channels increases 5 times and EVM is obviously improved.

  • 2252.
    Zhang, Lu
    et al.
    KTH. Shanghai Jiao Tong Univ, State Key Lab Adv Opt Commun Syst & Networks, Shanghai, Peoples R China..
    Pang, Xiaodan
    KTH. RISE Acreo AB, Networking & Transmiss Lab, Kista, Sweden..
    Ozolins, Oskars
    RISE Acreo AB, Networking & Transmiss Lab, Kista, Sweden..
    Udalcovs, Aleksejs
    RISE Acreo AB, Networking & Transmiss Lab, Kista, Sweden..
    Popov, Sergei
    KTH.
    Xiao, Shilin
    Shanghai Jiao Tong Univ, State Key Lab Adv Opt Commun Syst & Networks, Shanghai, Peoples R China..
    Chen, Jiajia
    KTH.
    K-means Clustering based Multi-Dimensional Quantization Scheme for Digital Mobile Fronthaul2018In: 2018 Optical Fiber Communications Conference and Exposition, OFC 2018 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018Conference paper (Refereed)
    Abstract [en]

    We propose to group highly-correlated neighboring samples into multi-dimensional vectors and adopt k-means clustering for quantization in mobile fronthaul. 30-Gbit/s transmissions have been experimentally demonstrated for up to 40 100MHz LTE channels over 20km fiber.

  • 2253.
    Zhang, Lu
    et al.
    KTH. Shanghai Jiao Tong University, Shanghai, China.
    Pang, Xiaodan
    KTH. RISE Acreo AB, Networking & Transmiss Lab, S-16425 Kista, Sweden.
    Ozolins, Oskars
    Udalcovs, Aleksejs
    Popov, Sergei
    Xiao, Shilin
    Hu, Weisheng
    Chen, Jiajia
    KTH. South China Normal Univ, South China Acad Adv Optoelect, MOE Int Lab Opt Informat Technol, Guangzhou 510006, Guangdong, Peoples R China.
    Spectrally efficient digitized radio-over-fiber system with k-means clustering-based multidimensional quantization.2018In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 43, no 7, p. 1546-1549Article in journal (Refereed)
    Abstract [en]

    We propose a spectrally efficient digitized radio-over-fiber (D-RoF) system by grouping highly correlated neighboring samples of the analog signals into multidimensional vectors, where the k-means clustering algorithm is adopted for adaptive quantization. A 30  Gbit/s D-RoF system is experimentally demonstrated to validate the proposed scheme, reporting a carrier aggregation of up to 40 100 MHz orthogonal frequency division multiplexing (OFDM) channels with quadrate amplitude modulation (QAM) order of 4 and an aggregation of 10 100 MHz OFDM channels with a QAM order of 16384. The equivalent common public radio interface rates from 37 to 150  Gbit/s are supported. Besides, the error vector magnitude (EVM) of 8% is achieved with the number of quantization bits of 4, and the EVM can be further reduced to 1% by increasing the number of quantization bits to 7. Compared with conventional pulse coding modulation-based D-RoF systems, the proposed D-RoF system improves the signal-to-noise-ratio up to ∼9  dB and greatly reduces the EVM, given the same number of quantization bits.

  • 2254.
    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.

  • 2255.
    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.

  • 2256.
    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.

  • 2257.
    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, p. 77-80Conference 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.

  • 2258.
    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, p. 3678-3689Article 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.

  • 2259.
    Zhang, Xinlin
    et al.
    Chalmers, Dept Signals & Syst, S-41296 Gothenburg, Sweden..
    Matthaiou, Michail
    Chalmers, Dept Signals & Syst, S-41296 Gothenburg, Sweden.;Queens Univ Belfast, Sch Elect Elect Engn & Comp Sci, Belfast, Antrim, North Ireland..
    Björnson, Emil
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Coldrey, Mikael
    Ericsson AB, Ericsson Res, Gothenburg, Sweden..
    Debbah, Merouane
    SUPELEC, Alcatel Lucent Chair Flexible Radio, Gif Sur Yvette, France..
    On the MIMO Capacity with Residual Transceiver Hardware Impairments2014In: 2014 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC) / [ed] Jamalipour, A Deng, DJ, IEEE , 2014, p. 5299-5305Conference paper (Refereed)
    Abstract [en]

    Radio-frequency (RF) impairments in the transceiver hardware of communication systems (e.g., phase noise (PN), high power amplifier (HPA) nonlinearities, or in-phase/quadrature-phase (I/Q) imbalance) can severely degrade the performance of traditional multiple-input multiple-output (MIMO) systems. Although calibration algorithms can partially compensate these impairments, the remaining distortion still has substantial impact. Despite this, most prior works have not analyzed this type of distortion. In this paper, we investigate the impact of residual transceiver hardware impairments on the MIMO system performance. In particular, we consider a transceiver impairment model, which has been experimentally validated, and derive analytical ergodic capacity expressions for both exact and high signal-to-noise ratios (SNRs). We demonstrate that the capacity saturates in the high-SNR regime, thereby creating a finite capacity ceiling. We also present a linear approximation for the ergodic capacity in the low-SNR regime, and show that impairments have only a second-order impact on the capacity. Furthermore, we analyze the effect of transceiver impairments on large-scale MIMO systems; interestingly, we prove that if one increases the number of antennas at one side only, the capacity behaves similar to the finite-dimensional case. On the contrary, if the number of antennas on both sides increases with a fixed ratio, the capacity ceiling vanishes; thus, impairments cause only a bounded offset in the capacity compared to the ideal transceiver hardware case.

  • 2260. 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, p. 1-3Conference 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.

  • 2261. 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, p. 19990-19995Article 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.

  • 2262. 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.

  • 2263.
    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.

  • 2264.
    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.

  • 2265. 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, p. 4467-4471Article 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.

  • 2266.
    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, p. 1103-1121Article 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.

  • 2267.
    Zhao, Hao
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Secure Management of Multi-Application Mobile Platforms2014Doctoral thesis, monograph (Other academic)
  • 2268.
    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, p. 54-58Conference 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™.

  • 2269.
    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, p. 32-35Article in journal (Refereed)
  • 2270.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Zander, O.
    Bolin, T.
    Ying, Z.
    EIRP of user equipment with beam forming capabilities at 28 GHz2018In: IET Conference Publications, Institution of Engineering and Technology , 2018, no CP741Conference paper (Refereed)
    Abstract [en]

    The equivalent isotropic radiated power (EIRP) has been used for defining the user equipment (UE) power class in millimeter wave (mmWave) frequencies in 3rd generation partnership project (3GPP) discussion since high directional antenna array systems with beamforming capability will be used in UE for future cellular communications. In this paper, we first briefly review the progress of 3GPP standardization on mmWave UE. Then, the EIRP of UE at 28 GHz with possible array topologies, in possible use cases, with imperfect precoders and the measurement uncertainties are discussed.

  • 2271.
    Zhao, Peiyue
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Dán, György
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    A Benders Decomposition Approach for Resilient Placement of Virtual Process Control Functions in Mobile Edge Clouds2018In: IEEE Transactions on Network and Service Management, ISSN 1932-4537, E-ISSN 1932-4537, Vol. 15, no 4, p. 1460-1472Article in journal (Refereed)
    Abstract [en]

    Replacing hardware controllers with software-based virtual process control functions (VPFs) is a promising approach for improving the operational efficiency and flexibility of industrial control systems. VPFs can be executed in edge clouds in 5G mobile networks or in the wireless backhaul, which can further improve efficiency. Nonetheless, for the acceptance of virtualization in industrial control systems, a fundamental challenge is to ensure that the placement of VPFs be resilient to component failures and cyber-attacks, besides being efficient. In this paper we address this challenge by considering that VPF placement costs are incurred by reserving mobile edge computing (MEC) resources, executing VPF instances, and by data communication. We formulate the VPF placement problem as an integer programming problem, considering resilience as a constraint. We propose a solution based on generalized Benders decomposition and based on linear relaxation of the resulting sub-problems, which effectively reduces the number of integer variables to the number of MEC nodes. We evaluate the proposed solution with respect to operational cost, efficiency, and scalability in a simulated metropolitan area. Our results show that the proposed solution reduces the total cost significantly compared to a greedy baseline algorithm and a local search heuristic, and can scale to moderate problem instances.

  • 2272.
    Zhao, Peiyue
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Dán, György
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Scheduling Parallel Migration of Virtualized Services under Time Constraints in Mobile Edge Clouds2019In: Proceedings of the 31st International Teletraffic Congress, ITC 2019, 2019, p. 28-36, article id 8879427Conference paper (Refereed)
    Abstract [en]

    Migrating virtualized services (VSs) in mobile edge clouds is essential for maintaining service quality under mobility, for optimizing resource utilization, and for responding to incidents. We consider migrating VSs with heterogeneous resource requirements from a source placement to a target placement under a time constraint, while maintaining service continuity as much as possible. We formulate the VS migration problem as an integer programming problem, and propose an efficient algorithm to compute sequences of migration actions. The algorithm is based on a graphical representation of the VS dependencies, and constructs a collection of acyclic directed hypergraphs with bounded length. We evaluate our algorithm in realistic scenarios and compare it to the optimal solution and to a baseline algorithm. Extensive simulations show that our algorithm achieves near-optimal performance, and is computationally efficient and scalable.

  • 2273.
    Zhao, Peiyue
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Fodor, Gabor
    Ericsson Res, S-16480 Stockholm, Sweden..
    Dan, Gyorgy
    Budapest University of Technology and Economics, Budapest, Hungary.
    Telek, Miklos
    MTA BME Informat Syst Res Grp, H-1117 Budapest, Hungary.
    A Game Theoretic Approach to Setting the Pilot Power Ratio in Multi-User MIMO Systems2018In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 66, no 3, p. 999-1012Article in journal (Refereed)
    Abstract [en]

    We consider the uplink of a single cell multi-user multiple input multiple output (MU-MIMO) system, in which the base station acquires channel state information at the receiver by means of uplink pilot signals. Since each mobile station has a sum power budget that is used to transmit pilot and data symbols, the pilot power ratio (PPR) has a large impact on the system performance in terms of spectral and energy efficiency. We formulate the problem of PPR setting as a non-cooperative game, in which each mobile station aims at minimizing the mean squared error of the uplink received data symbols at the base station. We show that in this game a unique Nash equilibrium exists, and propose an iterative decentralized algorithm-termed best PPR algorithm (BPA)-that is guaranteed to converge to that Nash equilibrium. Since BPA dynamically responds to the measured interference, it outperforms widely used schemes that use a predetermined PPR. BPA also performs close to the global optimum, especially when mobile stations with similar path loss values are co-scheduled in the MU-MIMO system. Based on these insights, we propose a practical signaling mechanism for implementing BPA in MU-MIMO systems.

  • 2274.
    Zhao, Peiyue
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Dán, György
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering.
    Telek, Miklos
    Budapest Univ Technol & Econ, H-1117 Budapest, Hungary.;MTA BME Informat Syst Res Grp, H-1117 Budapest, Hungary..
    A Game Theoretic Approach to Uplink Pilot and Data Power Control in Multi-Cell Multi-User MIMO Systems2019In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 68, no 9, p. 8707-8720Article in journal (Refereed)
    Abstract [en]

    In multi-user multiple-input-multiple-output (MU-MIMO) systems that employ pilot-symbol aided channel estimation, the pilot-to-data power ratio (PDPR) has a large impact on the system performance. In this paper, we consider the problem of setting the PDPR in multi-cell MU-MIMO systems in the presence of channel estimation errors, intercell interference and pilot contamination. To analyze and address this problem, we first develop a model of the multi-cell MU-MIMO system and derive a closed-form expression for the mean squared error of the uplink received data symbols. Building on this result, we then propose two decentralized PDPR-setting algorithms based on game theoretic approaches that are applicable in multi-cell systems. We find that both algorithms converge to a Nash equilibrium and provide performance improvements over systems that do not properly set the PDPR, while they maintain different levels of fairness.

  • 2275.
    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.

  • 2276.
    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)
  • 2277.
    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.

  • 2278. 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, p. 18-25Article 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.

  • 2279. 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, p. 13-16, article id 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.

  • 2280. 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, p. 16-18, article id 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.

  • 2281. 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, p. 681-686Article 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.

  • 2282.
    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.

  • 2283. 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, p. 329-333Conference 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.

  • 2284.
    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, p. 257-260Article 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.

  • 2285.
    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, p. 1629-1633Conference 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.

  • 2286.
    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, p. 3130-3143Article 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.

  • 2287.
    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, p. 56-58Article 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.

  • 2288.
    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.

  • 2289.
    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, p. 927-934Conference 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.

  • 2290.
    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.

  • 2291. 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, p. 1-5Conference 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.

  • 2292. 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, p. 445-449, article id 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.

  • 2293.
    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.

  • 2294.
    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, p. 1721-1726Conference 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.

  • 2295.
    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.

  • 2296. 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, IEEE, 2011, p. 13-18Conference 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.

  • 2297.
    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.

  • 2298.
    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.

  • 2299.
    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.

  • 2300.
    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.

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