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  • 2201.
    Zenteno, Efrain
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Amin, Shoaib
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Isaksson, Magnus
    Händel, Peter
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Combating the Dimensionality of Nonlinear MIMOAmplifier Predistortion by Basis Pursuit2014Ingår i: Proceedings of the 44th European Microwave Conference, 2014, s. 833-836Konferensbidrag (Refereegranskat)
    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.

  • 2202.
    Zerouali, Mehdi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    VoIP Communications over WLANs: Implementation of a new downlink transmission protocol2010Rapport (Övrigt vetenskapligt)
    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.

  • 2203.
    Zetterberg, Per
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Comparison of angle-spread in outdoor-to-outdoor and outdoor-to-indoor cases in an urban macro-cesll2005Ingår i: Wireless Personal Multimedia Communications (WPMC), Aalborg, Denmark, 2005Konferensbidrag (Refereegranskat)
  • 2204.
    Zetterberg, Per
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Method for Decreasing Fading in a Telecommunication System1998Patent (Övrig (populärvetenskap, debatt, mm))
    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.

  • 2205. Zetterberg, Per
    Performance of narrow beams in an suburban environment2000Ingår i: Vehicular Technology Conferance (VTC 2000-Spring), 2000, s. 1235-1239Konferensbidrag (Refereegranskat)
  • 2206.
    Zetterberg, Per
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fardi, Ramin
    Open Source SDR Frontend and Measurements for 60-GHz Wireless Experimentation2015Ingår i: IEEE Access, E-ISSN 2169-3536, Vol. 3, s. 445-456Artikel i tidskrift (Refereegranskat)
    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.

  • 2207.
    Zetterberg, Per
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jaldén, Niklas
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Investigation of Simple Algorithms for Estimation of Delay-Spread and Angle-Spread2012Rapport (Övrigt vetenskapligt)
    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.

  • 2208.
    Zetterberg, Per
    et al.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Ottersten, Björn
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    The Spectrum Efficiency of a Base Station Antenna Array System for Spatially Selective Transmission1995Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 44, nr 3, s. 651-660Artikel i tidskrift (Refereegranskat)
    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

  • 2209.
    Zhai, Chuanying
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zou, Zhuo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zheng, Lirong
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Software defined radio IR-UWB positioning platform for RFID and WSN application2012Ingår i: Ultra-Wideband (ICUWB), 2012 IEEE International Conference on, IEEE , 2012, s. 501-505Konferensbidrag (Refereegranskat)
    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.

  • 2210.
    Zhai, Chuanying
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zou, Zhuo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Industriell och Medicinsk Elektronik. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zhou, Qin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Mao, Jia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Chen, Qiang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Industriell och Medicinsk Elektronik. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Tenhunen, Hannu
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Industriell och Medicinsk Elektronik. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zheng, Lirong
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Industriell och Medicinsk Elektronik. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, 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 Things2017Ingår i: Enterprise Information Systems, ISSN 1751-7575, E-ISSN 1751-7583, Vol. 11, nr 6, s. 909-926Artikel i tidskrift (Refereegranskat)
    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.

  • 2211.
    Zhai, Chuanying
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zou, Zhuo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zhou, Qin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zheng, Lirong
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    A Software Defined Radio platform for passive UWB-RFID localization2012Ingår i: 2012 IEEE International Conference on Wireless Information Technology and Systems, ICWITS 2012, IEEE , 2012, s. 6417741-Konferensbidrag (Refereegranskat)
    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.

  • 2212. Zhang, Charlie Jianzhong
    et al.
    Ma, Jianglei
    Li, Geoffrey Ye
    Georgia Tech, Sch ECE, Atlanta, GA USA..
    Yu, Wei
    Univ Toronto, Toronto, ON, Canada..
    Jindal, Nihar
    Univ Calif Berkeley, Elet Engn Comp Sci, Berkeley, CA USA..
    Kishiyama, Yoshihisa
    NTT DoCoMo, INC, Toyota, Japan..
    Parkvall, Stefan
    KTH. Royal Inst Technol, Stockholm, Sweden..
    New Waveforms for 5G Networks2016Ingår i: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 54, nr 11, s. 64-65Artikel i tidskrift (Övrigt vetenskapligt)
  • 2213.
    Zhang, Feng
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster.
    Secure Mobile Service-Oriented Architecture2012Doktorsavhandling, monografi (Övrigt vetenskapligt)
    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.

  • 2214.
    Zhang, Feng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Kondoro, Aron
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Muftic, Sead
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Location-based authentication and authorization using smart phones2012Ingår i: 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, s. 1285-1292Konferensbidrag (Refereegranskat)
    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.

  • 2215.
    Zhang, Feng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Kounelis, Ioannis
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Muftic, Sead
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Generic, secure and modular (GSM) methodology for design and implementation of secure mobile applications2012Ingår i: SECURWARE 2012 - 6th International Conference on Emerging Security Information, Systems and Technologies, Rome, Italy: International Academy, Research and Industry Association (IARIA), 2012, s. 1-6Konferensbidrag (Refereegranskat)
    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.

  • 2216.
    Zhang, Feng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Telekommunikationssystem, TSLab.
    Muftic, Sead
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Telekommunikationssystem, TSLab.
    Schmöelzer, Gernot
    Secure Service-Oriented Architecture for Mobile Transactions2011Ingår i: World Congress on Internet Security (WorldCIS-2011), London: IEEE Communications Society, 2011, s. 133-138Konferensbidrag (Refereegranskat)
    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.

  • 2217.
    Zhang, Hengchong
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Non-binary Authentication: Supplicant2009Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Det finns ett antal metoder för trådlösa lokala nätverk. IEEE 802.1x-standarden är en sådan metod. Denna standard anger en port-baserad passagekontroll protokollet. Det finns tre enheter som är inblandade: en supplikant (en enhet som vill ha tillträde till nät och kanske andra tjänster), ett Access Point (AP) eller annan hamn som tillgång är att vara kontrollerad, och en Authentication Server (AS). Målet med projektet var att utforma, genomföra och utvärdera en prototyp av en icke-binära alternativ till IEEE 802.1x-autentisering. Denna rapport fokuserar på supplikant. Specifikt beskrivs utformning, genomförande och utvärdering av en supplikant program för att testa och betona authenticator, för att utvärdera ett icke-binära autentiseringsprocessen.

    Efter en kort introduktion ges till de problem som ska lösas, ett antal befintliga IEEE 802.1x supplikants beskrivs och jämförs. Efter detta har ett antal potentiella icke-binära autentisering processer analyseras. Möjligheten för en supplikant att skicka och ta emot paket före och efter autentisering är också undersökas. Baserat på vårt genomförande och utvärdering av en supplikant och en emulering av den icke-binära autentisering kan vi dra slutsatsen att icke-binära autentisering är både möjligt och värdefullt. Dessutom, avhandlingen utvärderar varför och hur icke-binära autentisering är värdefull ur ett supplikant. Ytterligare framtida arbetet föreslås i slutet av denna uppsats.

  • 2218.
    Zhang, Jianjun
    et al.
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Huang, Yongming
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Xiao, Ming
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Wang, Jiaheng
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Yang, Luxi
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Energy-Efficient Cooperative Hybrid Precoding for Millimeter-wave Communication Networks2018Ingår i: 2018 IEEE Global Communications Conference, GLOBECOM 2018 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018, artikel-id 8647975Konferensbidrag (Refereegranskat)
    Abstract [en]

    Millimeter wave (mmwave) communication operating in the band of 30-300 GHz is promising to provide Gbps data rates owing to its abundant spectrum resource, and has attracted increasing attention. Cooperative transmission, by converting undesired interferences into useful signals, is able to further improve performance of mmwave systems. In this paper, we propose a novel cooperative transmission scheme for mmwave communication networks, where each mobile user is cooperatively served by multiple access points (APs) that use hybrid precoders. Our goal is to maximize the system energy efficiency, which leverages on a joint design of the hybrid precoders of all APs. The formulated problem is a difficult nonlinear fractional programming subject to unit modulus constraints. We propose an efficient algorithm by incorporating penalty decomposition and block coordinate descent methods. Numerical results are provided to confirm the effectiveness of the proposed algorithm and reveal some important insights.

  • 2219.
    Zhang, Jianjun
    et al.
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Huang, Yongming
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Zhang, Cheng
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    He, Shiwen
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Yang, Luxi
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Cooperative Multi-Subarray Beam Training in Millimeter Wave Communication Systems2017Ingår i: Globecom 2017 - 2017 IEEE Global Communications Conference, Institute of Electrical and Electronics Engineers (IEEE), 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper studies beam training design for a codebook-based beamforming millimeter wave (mmwave) system where multiple antenna arrays are employed and each array is capable of beamforming independently. To reduce the training overhead and the complexity of subsequent beam direction search, we propose a cooperative multi-subarray beam training method. Specifically, from the perspective of excluding non-effective beam direction combinations and thus reducing search space, method and criterion of beam superposition are proposed to construct a wide beam from multiple narrow beams corresponding to multiple subarrays. Then, a cooperative multi-subarray beam training scheme is proposed based on the proposed criterion. Finally, simulation results show that the proposed scheme achieves a spectral efficiency close to that of the optimal exhaustive search scheme, while has greatly reduced training overhead and computational complexity.

  • 2220.
    Zhang, Kewei
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Papadimitratos, Panagiotis
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Analysis of the eect of the distance-decreasing aacks on GNSS authenticated signals2018Ingår i: WiSec 2018 - Proceedings of the 11th ACM Conference on Security and Privacy in Wireless and Mobile Networks, Association for Computing Machinery, Inc , 2018, s. 285-286Konferensbidrag (Refereegranskat)
    Abstract [en]

    Global Navigation Satellite Systems (GNSS) are vulnerable to jamming, spoong and replaying aacks because of their characteristics. Concerns regarding these aacks are being heightened because unmanned and autonomous vehicles become popular recently. Cryptographic methods have been proposed and are to be implemented in the Galileo and the GPS systems to counter spoong aacks. However, replaying aacks could still potentially harm GNSS receivers by bypassing the cryptographic methods. Distance-decreasing aacks is a strong type of replay aacks: it essentially resolves, from the aacker's point of view, the issue of introducing processing delay by implementing two phases: early detection and late commit. is poster analyzes the feasibility of distance-decreasing aacks against the GNSS navigation message authenticated signals and proposes countermeasures.

  • 2221. Zhang, L.
    et al.
    Wang, T.
    Liu, Q.
    Hu, X.
    Wang, Jing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Su, Y.
    Increasing the delay-bit rate product on silicon chip using Star-16QAM signal with high spectral efficiency2009Ingår i: Optical Transmission Systems, Switching, and Subsystems VII, 2009, s. 763204-Konferensbidrag (Refereegranskat)
    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.

  • 2222. Zhang, L.
    et al.
    Wang, T.
    Liu, Q.
    Hu, X.
    Wang, Jing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Su, Y.
    Increasing the delay-bit rate product on silicon chip using star-16QAM signal with high spectral efficiency2009Ingår i: 2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009, 2009Konferensbidrag (Refereegranskat)
    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.

  • 2223. Zhang, Lin
    et al.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Wu, Gang
    Zhao, Guodong
    Liang, Ying-Chang
    Li, Shaoqian
    Proactive Cross-Channel Gain Estimation for Spectrum Sharing in Cognitive Radio2016Ingår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 34, nr 10, s. 2776-2790Artikel i tidskrift (Refereegranskat)
    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.

  • 2224.
    Zhang, Lu
    et al.
    KTH. Shanghai Jiao Tong University, China.
    Pang, Xiaodan
    KTH. RISE Acreo AB, Sweden.
    Ozolins, O.
    Udalcovs, A.
    Popov, Sergei
    KTH.
    Xiao, S.
    Chen, Jiajia
    KTH.
    K-means clustering based multi-dimensional quantization scheme for digital mobile fronthaul2018Ingår i: Optics InfoBase Conference Papers, Optics Info Base, Optical Society of America, 2018Konferensbidrag (Refereegranskat)
    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.

  • 2225.
    Zhang, Lu
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT). Shanghai Jiao Tong University, Shanghai, China.
    Pang, Xiaodan
    KTH, Skolan för informations- och kommunikationsteknik (ICT). RISE Acreo AB, Kista, Sweden.
    Ozolins, O.
    Udalcovs, A.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Westergren, Urban
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Jacobsen, G.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Xiao, S.
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    15-Gbaud PAM4 Digital Mobile Fronthaul with Enhanced Differential Pulse Coding Modulation Supporting 122 LTE-A Channels with up to 4096QAM2018Ingår i: 2017 European Conference on Optical Communication (ECOC), Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 1-3Konferensbidrag (Refereegranskat)
    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.

  • 2226.
    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 Fronthaul2018Ingår i: 2018 Optical Fiber Communications Conference and Exposition, OFC 2018 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018Konferensbidrag (Refereegranskat)
    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.

  • 2227.
    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.2018Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 43, nr 7, s. 1546-1549Artikel i tidskrift (Refereegranskat)
    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.

  • 2228.
    Zhang, P.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Costa, J.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Tekeusso, Boris
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Wahlstrand, N.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Carmona, O.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    M2M Communications in LTE SystemsIngår i: Wireless networks, ISSN 1022-0038, E-ISSN 1572-8196Artikel i tidskrift (Övrigt vetenskapligt)
    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.

  • 2229.
    Zhang, Peng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Energy-Efficient Clustering Design for M2M Communications2014Ingår i: 2014 IEEE Global Conference on Signal and Information Processing (GlobalSIP), 2014Konferensbidrag (Refereegranskat)
    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.

  • 2230.
    Zhang, Shasha
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Device aggregation with data networking: Implementing a Personal Area Network2008Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Den snabba tekniska utvecklingen ger våra apparater mer och mer intelligens, priset på avancerade produkter är överkomligt och trådlösa infrastrukturer binder samman allt fler produkter.

    Tekniska produkter har blivit en del av vår vardag: Mobiltelefon, PDA-er, trådlösa hörlurar och tangentbord med blåtandsradio, GPS och digitalkameror. I takt med den tekniska utvecklingen kommer hela tiden nya intelligenta och kommunicerande produkter.

    Man kan hitta liknande funktioner i olika produkter, och det är svårt för den vanlige användaren att välja den optimala produkten. Dessutom har de avancerade produkterna många parametrar att ställa in, och att använda olika produkter tillsammans kräver att användaren är djupt insatt i tekniken. Genom att aggregera, koppla ihop, produkterna i ett lokalt nätverk, kan deras funktioner användas effektivt och göras bättre tillgängliga genom att de för användaren ser ut som om de tillhör en enda produkt.

    Denna avhandling introducerar en kommunikationsmodell baserad på produktaggregering genom delade gemensamma tillstånd och reaktioner hos de ingående produkterna, med tillägg av respektive produkters särskilda funktioner. En sådant logiskt produktaggregat kan också fås att utföra funktioner som användaren annars skulle ha väldigt svårt att realisera genom att manuellt kombinera de nödvändiga produktfunktionerna. Det underlättar alltså användningen av systemet (byggt av flera olika produkter), som fungerar som om det vore en enda produkt.

    Projektet har genomförts tillsammans med David Sabaté Mogica. Vi har utvecklat ett system för produktaggregering baserat på Dynamic Host Client protocol (DHCP) och Service Location Protocol (SLP) för att identifiera tillgängliga fuktioner och Virtual Network Computing (VNC) för ”remote desktop control”. Systemet är byggt i ett laboratorienät.

    Avhandlingen fokuserar på hur identifiering av tillgängliga funktioner och tjänster genomförs och utvärderas. ”Remote desktop control” utvecklades och infördes separat och kommer att rapporteras separat. Ömsesidig identifiering av funktioner mellan två datorer har genomförts med ett program utvecklat speciellt för en PDA. Hittils sänder emellertid PDA’n bara ett DA-frågepaket med DHCP. Den ömsesidiga funktionsidentifieringen är dock testad och fungerar mellan två datorer vilket gav den nödvändiga grunden för programmeringen av PDA’n och för framtida utveckling av liknande program för mobiltelefoner.

  • 2231.
    Zhang, Xi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Palomar, Daniel P.
    Dept. of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Robust design of linear MIMO transceivers under channel uncertainty2006Ingår i: 2006 IEEE International Conference on Acoustics, Speech, and Signal Processing: signal processing for communication, sensor array and multichannel signal processing, 2006, s. 77-80Konferensbidrag (Refereegranskat)
    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.

  • 2232.
    Zhang, Xi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Palomar, Daniel P.
    Electrical Engineering, Princeton University, Princeton.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Statistically robust design of linear MIMO transceivers2008Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 56, nr 8, s. 3678-3689Artikel i tidskrift (Refereegranskat)
    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.

  • 2233.
    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, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, 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 Impairments2014Ingår i: 2014 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC) / [ed] Jamalipour, A Deng, DJ, IEEE , 2014, s. 5299-5305Konferensbidrag (Refereegranskat)
    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.

  • 2234. 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 services2012Ingår i: Communications and Photonics Conference (ACP), 2012 Asia, Optical Society of America, 2012, s. 1-3Konferensbidrag (Refereegranskat)
    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.

  • 2235. 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 systems2012Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, nr 18, s. 19990-19995Artikel i tidskrift (Refereegranskat)
    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.

  • 2236. 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 estimation2012Ingår i: 2012 Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference, OFC/NFOEC 2012, 2012Konferensbidrag (Refereegranskat)
    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.

  • 2237.
    Zhang, Yan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Wireless sensor network for volcano monitoring2005Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Vulkaner har, i syfte för riskuppskattning, under en lång tid observerats med enkel sensorteknik.Det systemet behöver dock manuell övervakning av varje sensor, vilket gör att övervakningssystemet inte blir nog flexibelt eller effektivt för att kunna anpassas till en variabel vulkanmiljö. Med utvecklingen av trådlösa sensornätverk kan noggrannheten och täckningen av vulkanövervakning förbättras. I denna rapport föreslås en prototyp för ett trådlöst sensornätverk avsett för övervakning av vulkaner.Denna prototyp byggdes och provades i en fältkampanj på vulkanen Etna i september 2004. I denna rapport presenteras även hårdvarudesign av sensorer, fördjupad design av sensornätverket och arkitektur av mjukvarumoduler.Erfarenheten från det praktiska arbetet på Etna kommer att användas i ett kommande vulkanprojekt.

  • 2238.
    Zhang, Yuanhui
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Evaluating a publish/subscribe proxy for HTTP2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Med allt högre Internetshastighet och dess utbredda användning, uppvisar den aktuella Internet-arkitekturen vissa problem. Publicera / prenumerera paradigm har utvecklats för att stödja en av de vanligaste mönstren för kommunikation. Det gör att "information" blir centrum av kommunikation och tar bort "plats-identitet split" (dvs att objekten är på specifika platser som du måste kommunicera med för att komma åt objektet). i detta examensarbete byggs ett publicera / prenumerera nätverk och sedan används i utformningen, genomförandet, och utvärdering av en publicera / prenumerera proxy för dagens HTTP-baserad kommunikation. Genom att använda denna proxy kan användare kan använda sin befintliga webbläsare för att skicka både HTTP-förfrågningar och publicera / Prenumerera Internet Routing Paradigm (PSIRP) begäran. En publicera / prenumerera överlagring är ansvarig för att upprätthålla innehåll av PSIRP. Fullmakten gör det möjligt för klienter av webbläsare att dra nytta av publicera / prenumerera nätverket, utan att kräva dem att ändra sitt beteende eller ens vara medvetna om det faktum att det innehållet som de vill komma åt tillhandahålls via publicera / prenumerera överlägg. Användningen av överlägget kan en användare begäran som skall uppfyllas av en kopia av innehållet, eventuellt minskande latens, vilket minskar trafiken stamnät, och minska belastningen på det ursprungliga innehållet servern. Ett av syftena med denna uppsats är att göra mer PSIRP innehåll tillgängligt och detta görs genom att införa en proxy som hanterar både HTTP och PSIRP förfrågningar, men har fått innehåll som en följd av en HTTP-svar offentliggörs denna data som PSIRP tillgängligt innehåll. Syftet är att främja införandet och innehållbaserade åtkomsten.

  • 2239. Zhang, Zhengquan
    et al.
    Ma, Zheng
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ding, Zhiguo
    Fan, Pingzhi
    Full-Duplex Device-to-Device-Aided Cooperative Nonorthogonal Multiple Access2017Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 66, nr 5, s. 4467-4471Artikel i tidskrift (Refereegranskat)
    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.

  • 2240.
    Zhang, Zhi
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Lu, Zhonghai
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Chen, Qiang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Yan, Xiaolang
    Zheng, Li-Rong
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, 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 analysis2012Ingår i: International Journal of Communication Systems, ISSN 1074-5351, E-ISSN 1099-1131, Vol. 25, nr 9, s. 1103-1121Artikel i tidskrift (Refereegranskat)
    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.

  • 2241.
    Zhao, Hao
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Secure Management of Multi-Application Mobile Platforms2014Doktorsavhandling, monografi (Övrigt vetenskapligt)
  • 2242.
    Zhao, Hao
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Muftic, Sead
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    The concept of secure mobile wallet2011Ingår i: World Congress on Internet Security, WorldCIS-2011, 2011, s. 54-58Konferensbidrag (Refereegranskat)
    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™.

  • 2243.
    Zhao, Hao
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    Muftic, Sead
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    Zhang, Feng
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    The secure mobile wallet: Anytime, anywhere financial transactions2010Ingår i: Cutter IT Journal, ISSN 1522-7383, Vol. 23, nr 7, s. 32-35Artikel i tidskrift (Refereegranskat)
  • 2244.
    Zhao, Kun
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.
    Zander, O.
    Bolin, T.
    Ying, Z.
    EIRP of user equipment with beam forming capabilities at 28 GHz2018Ingår i: IET Conference Publications, Institution of Engineering and Technology , 2018, nr CP741Konferensbidrag (Refereegranskat)
    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.

  • 2245.
    Zhao, Peiyue
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Dán, György
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    A Benders Decomposition Approach for Resilient Placement of Virtual Process Control Functions in Mobile Edge Clouds2018Ingår i: IEEE Transactions on Network and Service Management, ISSN 1932-4537, E-ISSN 1932-4537, Vol. 15, nr 4, s. 1460-1472Artikel i tidskrift (Refereegranskat)
    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.

  • 2246.
    Zhao, Peiyue
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    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 Systems2018Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 66, nr 3, s. 999-1012Artikel i tidskrift (Refereegranskat)
    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.

  • 2247.
    Zhao, Peiyue
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Fodor, Gabor
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Dán, György
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    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 Systems2019Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 68, nr 9, s. 8707-8720Artikel i tidskrift (Refereegranskat)
    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.

  • 2248.
    Zhao, Wang
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Hu, JianHao
    Xiong, Xing Zhong
    Song, Jie
    Non-data-aided timing acquisition for asynchronous IDMA systems2012Ingår i: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. AprilArtikel i tidskrift (Refereegranskat)
    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.

  • 2249.
    Zhao, Wei
    et al.
    Ericsson Research.
    Andersson, Loa
    Ericsson AB.
    Sköldström, Pontus
    Acreo AB.
    Prototyping MPLS-TP forwarding and OAM2009Ingår i: 5th International Conference on IP + Optical Network, 2009Konferensbidrag (Refereegranskat)
  • 2250.
    Zhao, Xueqian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik och Inbyggda System.
    Network on Chip: Performance Bound and Tightness2015Doktorsavhandling, monografi (Övrigt vetenskapligt)
    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.

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