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  • 3101.
    Yu, Kan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Gidlund, Mikael
    ABB, Corporate Research.
    Åkerberg, Johan
    ABB, Corporate Research.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering.
    Reliable and Low Latency Transmission in Industrial Wireless Sensor Networks2011In: Procedia Computer Science, ISSN 1877-0509, E-ISSN 1877-0509, Vol. 5, 866-873 p.Article in journal (Refereed)
    Abstract [en]

    The major advantages with Industrial Wireless Sensor Networks (IWSNs) in process automation are cable cost reduction, enhanced flexibility and enabling new emerging applications such as wireless control. However, transmission over the wireless channel is prone to noise and interference which causes packets to be erroneous received at the receiver node. To improve the link reliability in lossy channels, error correcting codes are commonly used. In this paper we discuss the use of forward error correction (FEC) codes in IWSN in order not only to improve the link reliability but also to reduce the number of retransmissions in harsh industrial environments. We propose a FEC scheme suitable for MAC level protection where the packet is divided into groups and encoded using systematic FEC codes. We have implemented different FEC codes in a typical IWSN chip to evaluate memory consumption and to ensure that we are not violating the strict timing rules for acknowledgment. Our results show that some FEC codes are suitable to be implemented in a typical IWSN node while several fails due to large memory footprint or to long encoding and decoding time.

  • 3102.
    Yu, Kan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Gidlund, Mikael
    ABB, Corporate Research.
    Åkerberg, Johan
    ABB, Corporate Research.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering.
    Reliable RSS-based Routing Protocol for Industrial Wireless Sensor Networks2012In: IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society: Proceeding, 2012, 3231-3237 p.Conference paper (Refereed)
    Abstract [en]

    High reliability and real-time performance are main research challenges in Industrial Wireless Sensor Networks (IWSNs). Existing routing protocols applied in IWSNs are either overcomplicated or fail to fulfill the stringent requirements. In this paper, we propose a reliable and flexible Received Signal Strength-based routing scheme. Our proposed solution can achieve a seamless transition in the event of topology change and can be applied in different industrial environments. The simulation results show that our solution outperforms conventional routing protocols in both reliability and latency. Furthermore, the result also proves that the changes of the network topology have no impact on data transmissions of other nodes by our scheme, whereas conventional routing protocols are shown to fail to recover the network in a short time. Finally, due to dynamic weighting mechanism, the proposed scheme is verified to achieve significantly higher reliability in scenarios with obstacles and avoid installation troubles, compared to location-based flooding scheme. Thus, our proposed scheme is considered to be more suitable for IWSNs than other routing protocols.

  • 3103.
    Yu, Kan
    et al.
    Mälardalens Högskola.
    Zheng, Tao
    Beijing Jiatong University.
    Pang, Zhibo
    ABB Corporate Research.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Åkerberg, Johan
    ABB Corporate Research.
    Björkman, Mats
    Mälardalens Högskola.
    Reliable Flooding-based Downlink Transmissions for Industrial Wireless Sensor and Actuator Networks2013Conference paper (Refereed)
  • 3104.
    Yu, Kan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Åkerberg, Johan
    Corp Res, ABB AB, Sweden.
    Gidlund, Mikael
    Corp Res, ABB AB, Sweden.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering.
    Performance Evaluation and Measurement of REALFLOW Routing Protocol in WirelessIndustrial NetworksIn: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050Article in journal (Refereed)
    Abstract [en]

    Industrial Wireless Sensor and Actuator Networks(IWSAN) offer significant advantages to industrial automationsystems. Requirements on reliability are highly demanding formany industrial applications. Due to multipath diversity andsimplicity, flooding is an promising approach to provide reliabletransmissions.

    In this paper, a flooding-based routing protocol for IWSAN(REALFLOW) is upgraded based on previous research, aimingfor high reliability. To provide efficient and directionaltransmission, a controlled flooding-based mechanism is applied.Network management is further improved for better efficiencyand stability. REALFLOW is first compared with other fourflooding protocols via simulation. The results exhibit that REALFLOWoutperforms other advanced flooding protocols interms of reliability and consecutive transmission errors. Evencompared with pure flooding, REALFLOW achieves comparablereliability performance with decreased forwarding redundancy.To demonstrate the solution promising in reality, a workableIWSAN prototype is built, as well as the full implementation ofthe whole protocol stack including REALFLOW. A measurementconducted in a industrial manufacturing workshop reveals thathigh reliability and low application failure probability can beachieved, which brings more confidence of providing both reliablewireless sensing and actuating for industrial automation systems.

  • 3105.
    Yu, Tianyi
    et al.
    Halmstad University, School of Information Technology.
    Edén, Jenny
    Halmstad University, School of Information Technology.
    Englund, Cristofer
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), CAISR - Center for Applied Intelligent Systems Research. Viktoria Swedish ICT, Gothenburg, Sweden.
    Larsson, Tony
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Traffic Situation Estimator for Adaptive Cruise Control2016In: 2016 IEEE 17th International Symposium on A World of Wireless, Mobile and Multimedia Networks (WoWMoM), Piscataway, NJ: IEEE, 2016, 7523567Conference paper (Refereed)
    Abstract [en]

    A traffic situation estimator capable of analyzing driving behavior utilizing an image analysis-based tracking module is presented. The behavior is analyzed by using a state machine driven counter to estimate the traffic rhythm and determine if the detected vehicles are approaching, getting away, have been overtaken or have overtaken the ego-vehicle. Depending on the result, the traffic situation estimator suggest different reactions, either to drive faster, slower or optionally suggest to overtake vehicles ahead to help the driver to follow the traffic rhythm which in turn will improve safety and energy efficiency. The proposed approach is implemented in a smart-phone and has shown good performance while testing the application on a two-lane highway. © 2016 IEEE.

  • 3106. Yu, Xianbin
    et al.
    Jia, Shi
    Pang, Xiaodan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). RISE ACREO AB.
    Morioka, Toshio
    Oxenloewe, Leif K.
    Beyond 100 Gbit/s wireless connectivity enabled by THz photonics2017In: Transparent Optical Networks (ICTON), 2017 19th International Conference on, IEEE Computer Society, 2017, 1-4 p.Conference paper (Refereed)
    Abstract [en]

    Beyond 100Gbit/s wireless connectivity is appreciated in many scenarios, such as big data wireless cloud, ultrafast wireless download, large volume data transfer, etc. In this paper, we will present our recent achievements on beyond 100Gbit/s ultrafast terahertz (THz) wireless links enabled by THz photonics.

  • 3107. Yu, Xianbin
    et al.
    Zhao, Ying
    Deng, Lei
    Pang, Xiaodan
    RISE ACREO AB; Technical University of Denmark.
    Tafur Monroy, Idelfonso
    Existing PON Infrastructure Supported Hybrid Fiber-Wireless Sensor Networks2012In: National Fiber Optic Engineers Conference, NFOEC 2012, 2012Conference paper (Refereed)
    Abstract [en]

    We propose a hybrid fiber wireless sensor network based on the existing PON infrastructure. The feasibility of remote sensing and PON convergence is experimentally proven by transmitting direct-sequence spread-spectrum wireless sensing and 2.5Gbps GPON signals.

  • 3108.
    Yuan, Di
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Chen, Lei
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Karipidis, Eleftherios
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    On Optimal Link Activation with Interference Cancelation in Wireless Networking2013In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 62, no 2, 939-945 p.Article in journal (Refereed)
    Abstract [en]

    A fundamental aspect in performance engineering of wireless networks is optimizing the set of links that can be concurrently activated to meet given signal-to-interference-and-noise ratio (SINR) thresholds. The solution of this combinatorial problem is the key element in scheduling and cross-layer resource management. In this paper, we assume multiuser decoding receivers, which can cancel strongly interfering signals. As a result, in contrast to classical spatial reuse, links being close to each other are more likely to be active concurrently. Our focus is to gauge the gain of successive interference cancellation (SIC), as well as the simpler, yet instructive, case of parallel interference cancellation (PIC), in the context of optimal link activation. We show that both problems are NP-hard and develop compact integer linear programming formulations that enable to approach global optimality. We provide an extensive numerical performance evaluation, indicating that for low to medium SINR thresholds the improvement is quite substantial, especially with SIC, whereas for high SINR thresholds the improvement diminishes and both schemes perform equally well.

  • 3109.
    Yuan, Xiaolong
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Wu, X.
    Signell, S.
    Continuous-time quadrature bandpass sigma delta modulators with different feedback DAC2008In: IEEE Int. Conf. Circuits Syst. Commun., ICCSC, 2008, 580-583 p.Conference paper (Refereed)
    Abstract [en]

    Continuous time (CT) quadrature bandpass sigma delta modulators (QBSDM) are widely used in wireless receivers recently due to its inherent anti-aliasing filtering and complex filtering embedded in the loops to efficiently realize asymmetric noise-shaping. The complex noise-transfer-function (NTF) can be realized with complex coefficients or by implementing the loop as a cascade of complex integrators with only real coefficients, which is desirable due to its lower sensitivity to loop mismatch. In this paper, we will study the effect of different feedback waveforms inside the modulator on the NTF of quadrature sigma delta modulators. Complex NTF design is discussed for different bandpass center frequencies relative to the sampling frequency.

  • 3110.
    Yuan, Zhao
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Implementing zonal pricing in distribution network: The concept of pricing equivalence2016In: IEEE Power and Energy Society General Meeting, IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    Distribution locational marginal pricing (DLMP) is critical market mechanism to boost services from distributed energy resources (DER). This paper propose to design zonal pricing in distribution network according to the concept of pricing equivalence (PE). The rules of the zonal pricing are derived. We prove that equivalent load shift from demand response can be achieved by zonal pricing if pricing equivalence is deployed. Convex AC optimal power flow (OPF) is used to calculate zonal prices. The benefits of convex AC OPF are more accurate energy pricing and global optimization target. The responsive load with passive load controllers are modeled and solved in GAMS platform. Different zonal pricing approaches (PE, reference node and average of nodal prices) are compared. IEEE 14-bus network and two IEEE 13-node networks are connected to be an illustrative test case offering numerical results. The results show that zonal pricing designed according to PE can achieve the same load shift effects and quite close consumer payments as nodal pricing. PE outperform other zonal pricing approaches prominently in congested network situations.

  • 3111. Yun, S. -Y
    et al.
    Proutiere, Alexandre
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Distributed proportional fair load balancing in heterogenous systems2015In: Performance Evaluation Review, ACM Press, 2015, Vol. 43, no 1, 17-30 p.Conference paper (Refereed)
    Abstract [en]

    We consider the problem of distributed load balancing in heterogenous parallel server systems, where the service rate achieved by a user at a server depends on both the user and the server. Such heterogeneity typically arises in wireless networks (e.g., servers may represent frequency bands, and the service rate of a user varies across bands). We assume that each server equally shares in time its capacity among users allocated to it. Users initially attach to an arbitrary server, but at random instants of time, they probe the load at a new server and migrate there if this improves their service rate. The dynamics under this distributed load balancing scheme, referred to as Random Local Search (RLS), may be interpreted as those generated by strategic players updating their strategy in a load balancing game. In closed systems, where the user population is fixed, we show that this game has pure Nash Equilibriums (NEs), and that these equilibriums get close to a Proportionally Fair (PF) allocation of users to servers when the user population grows large. We provide an anytime upper bound of the gap between the allocation under RLS and the PF allocation. In open systems, where users randomly enter the system and leave upon service completion, we establish that the RLS algorithm stabilizes the system whenever this it at all possible under centralized load balancing schemes, i.e., it is throughput-optimal. The proof of this result relies on a novel Lyapounov analysis that captures the dynamics due to both users’ migration and their arrivals and departures. To our knowledge, the RLS algorithm constitutes the first fully distributed and throughputoptimal load balancing scheme in heterogenous parallel server systems. We extend our analysis to various scenarios, e.g. to cases where users can be simultaneously served by several servers. Finally we illustrate through numerical experiments the efficiency of the RLS algorithm.

  • 3112.
    Yunda Lozano, Daniel
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Improving vertical handover performance for RTP streams containing voice: Using network parameters to predict future network conditions in order to make a vertical handover decision2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wireless local area networks WLAN and Voice over IP technologies enable local low cost wireless telephony, while cellular networks offer wide-area coverage. The use of dual mode WLAN-cellular terminals should allow cost savings by automatically switching from GSM to WLAN networks whenever it is feasible. However, in order to allow user mobility during a call, a handover procedure for transferring a call between the WLAN interface and the cellular network should be defined. The decision algorithm that triggers such a handover is critical to maintain voice quality and uninterrupted communication. Information or measurements collected from the network may be used to anticipate when the connection will degrade to such a point that a handover is desirable in order to allow a sufficient time span for the handover’s successful execution. It is the delay in detecting when to make a handover and the time to execute it that motivates the need for a prediction.

    The goal of this thesis is therefore to present a method to predict when a handover should be made based upon network conditions. We selected a number of WLAN and VoIP software tools and adapted them to perform the measurements. These tools allowed us to measure parameters of the WLAN’s physical and link layers. Packet losses and jitter measurements were used as well. We have assumed that there is ubiquitous cellular coverage so that we only have to be concerned with upward handovers (i.e, from the WLAN to the cellular network and not the reverse). Finally we have designed and evaluated a mechanism that triggers the handover based in these measurements.

  • 3113.
    Zachariah, Dave
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Dwivedi, Satyam
    KTH Royal Inst Technol, Dept Elect Engn, SE-10044 Stockholm, Sweden..
    Handel, Peter
    KTH Royal Inst Technol, Dept Elect Engn, SE-10044 Stockholm, Sweden..
    Stoica, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Scalable and Passive Wireless Network Clock Synchronization in LOS Environments2017In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, no 6, 3536-3546 p.Article in journal (Refereed)
    Abstract [en]

    Clock synchronization is ubiquitous in wireless systems for communication, sensing, and control. In this paper, we design a scalable system in which an indefinite number of passively receiving wireless units can synchronize to a single master clock at the level of discrete clock ticks. Accurate synchronization requires an estimate of the node positions to compensate the time-of-flight transmission delay in line-of-sight environments. If such information is available, the framework developed here takes position uncertainties into account. In the absence of such information, as in indoor scenarios, we propose an auxiliary localization mechanism. Furthermore, we derive the Cramer-Rao bounds for the system, which show that it enables synchronization accuracy at sub-nanosecond levels. Finally, we develop and evaluate an online estimation method, which is statistically efficient.

  • 3114. Zafar, B.
    et al.
    Ben Slimane, Slimane
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Communication Systems, CoS (closed 2012-01-01).
    Javed, Muhammad Umar
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Communication Systems, CoS (closed 2012-01-01).
    Network product coding2010In: 2010 7th IEEE Consumer Communications and Networking Conference, CCNC 2010, IEEE , 2010, -266 p.Conference paper (Refereed)
    Abstract [en]

    Network coding is a useful tool to increase the multicast capacity of networks. The traditional approach to network coding involving XOR operation has several limitations such as low robustness and can support only two users/packets at a time,per relay, in the mixing process to achieve optimal error performance. We propose the employment of product coding at the relay station instead of xor and investigate such a system where we use the relay to generate product codes by combining packets from different users. Our scheme uses relays to transmit only the redundancy of the product code instead of the whole product code. We seek to employ product coding can be able to support more than two users/packets per relay per slot, while maintaining a good error performance. Our scheme can accomodate as many users per relay as the costituent block code allows, thus reducing the number of relays required in the network.Product codes also offer increased robustness and flexibility as well as several other advantages, such as proper structure for burst error correction without extra interleaving. We compare the performance of such a scheme to the conventional xor scheme and see that our scheme not only reduces the number of relays required but gives improved error performance as well as. Another encouraging result is that our scheme starts to significantly outperform the conventional one by introducing a gain at the relay.

  • 3115.
    Zafar, Bilal
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Network Coding Employing Product Coding at Relay Stations2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Network coding is a useful tool to increase the multicast capacity of networks. The traditional approach to network coding involving XOR operation has several limitations such as low robustness and can support only two users/packets at a time,per relay, in the mixing process to achieve optimal error performance. We propose the employment of product coding at the relay station instead of xor and investigate such a system where we use the relay to generate product codes by combining packets from different users.Our scheme uses relays to transmit only the redundancy of the product code instead of the whole product code.We seek to employ product coding can be able to support more than two users/packets per relay per slot,while maintaining a good error performance. Our scheme can accomodate as many users per relay as the costituent block code allows, thus reducing the number of relays required in the network. Product codes also offer increased robustness and flexibility as well as several other advantages, such as proper structure for burst error correction without extra interleaving. We compare the performance of such a scheme to the conventional xor scheme and see that our scheme not only reduces the number of relays required but gives improved error performance as well as. Another encouraging result is that our scheme starts to significantly outperform the conventional one by introducing a gain at the relay.

  • 3116.
    Zahidi, Salman
    Linköping University, Department of Electrical Engineering, Information Coding.
    Biometrics - Evaluation of Current Situation2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Information security has always been a topic of concern in the world as an emphasis on new techniques to secure the identity of a legitimate user is regarded as top priority. To counter such an issue, we have a traditional way of authentication factors “what you have” and “what you know” in the form of smart cards or passwords respectively. But biometrics is based on the factor “who are you” by analyzing human physical or behavioral characteristics. Biometrics has always been an efficient way of authorization and is now considered as a $1500 million industry where fingerprints dominate the biometrics while iris is quickly emerging as the most desirable form of biometric technique.The main goal of this thesis is to compare and evaluate different biometrics techniques in terms of their purpose, recognition mechanism, market value and their application areas. Since there are no defined evaluating criteria, my method of evaluation was based on a literature survey from internet, books, IEEE papers and technical surveys. Chapter 3 is focused on different biometrics techniques where I discuss them briefly but in chapter 4, I go deeper into Iris, fingerprints, facial techniques which are prominent in biometrics world. Lastly, I had a general assessment of the biometrics, their future growth and suggested specific techniques for different environment like access controls, e-commerce, national ids, and surveillance.

  • 3117. Zaidi, A. A.
    et al.
    Oechtering, Tobias J.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Stabilization of noisy plants over a Gaussian interference channel2014In: IWCIT 2014 - Iran Workshop on Communication and Information Theory, 2014Conference paper (Refereed)
    Abstract [en]

    Remote stabilization of two noisy linear plants over a symmetric Gaussian interference channel with possibly noisy feedback from controllers to the plants is studied. Each plant is monitored by a separate sensor which communicates its observations to a separate controller over a Gaussian interference channel. The controllers aim at stabilizing the two plants in mean-square sense. The plant noise is assumed to be additive white Gaussian distributed. A delay-free sensing and control scheme is proposed, which is an adaptation of the Schalkwijk-Kailath type coding schemes developed for transmission of reliable information over channels with noiseless feedback. The conditions that guarantee the stabilization of the noisy plants under the proposed scheme are derived, extending the results that are known for mean-square stabilization of noiseless plants over noiseless feedback channels. Numerical results indicate that the stabilizability is not affected by the inclusion of an additive Gaussian noise in the plant models under the proposed scheme.

  • 3118.
    Zaki, Ahmed
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Wang, Chao
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Combining interference alignment and Alamouti codes for the 3-user MIMO interference channel2013In: 2013 IEEE Wireless Communications and Networking Conference (WCNC), New York: IEEE , 2013, 3563-3567 p.Conference paper (Refereed)
    Abstract [en]

    The interference channel (IC) is the basic underlying channel model for many practical multi-terminal communication scenarios. Here, we consider a modified three-user IC with dual-antenna transmitters and receivers where we allow one receiver to have a finite-rate unidirectional link to another receiver. This kind of receiver-to-receiver link may exist in cellular networks with base-station backhaul. For this scenario we propose a scheme that combines the interference-cancellation capability of Alamouti codes with the subspace-overlapping property of interference alignment to achieve a sum-rate of three symbols/channel use. The scheme does also simultaneously provide a diversity gain of two for every symbol which significantly improves the bit-error rate performance compared to zero-forcing techniques.

  • 3119.
    Zamaere, Bruce
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Hidell, Markus
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Sjödin, Peter
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    CVPN: A multi-homed VPN solution for remote patient monitoring2012In: 2012 IEEE 14th International Conference on e-Health Networking, Applications and Services, Healthcom 2012, IEEE , 2012, 279-285 p.Conference paper (Refereed)
    Abstract [en]

    This paper addresses the challenges of reliably, and securely, extending a healthcare provider's network into the homes of its patients in order to provide Remote Patient Monitoring (RPM) services. It describes the Carenet Virtual Private Network (CVPN) solution, a multi-homed VPN solution implemented as a virtual device driver under Linux. We describe CVPN's architecture and implementation, motivating its design decisions. The initial experimental evaluation, of our proof-of-concept prototype, shows that CVPN's per packet overhead, forwarding delay, and fail-over time are reasonable for healthcare monitoring applications and time-sensitive synchronous communications.

  • 3120.
    Zander, Jens
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Mähönen, Petri
    Riding the Data Tsunami in the Cloud: Myths and Challenges in Future Wireless Access2013In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 51, no 3, 145-151 p.Article in journal (Refereed)
    Abstract [en]

    Data rates of mobile communications have increased dramatically during the last decade. The industry predicts an exponential increase of data traffic that would correspond to a 1000-fold increase in traffic between 2010 and 2020. These figures are very similar to ones reported during the last Internet boom. In this article we assess the realism of these assumptions. We conjecture that wireless and mobile Internet access will emerge as a dominant technology. A necessary prerequisite for this development is that wireless access is abundant and becomes (almost) free. A consequence is that the projected capacity increase must be provided at the same cost and energy consumption as today. We explore technical and architectural solutions that have realistic possibility to achieve these targets. We ask if Moore's law, which has successfully predicted the tremendous advances in computing and signal processing, will also save the day for high-speed wireless access. We argue that further improvements of the PHY layer are possible, but it is unlikely that this alone provides a viable path. The exponential traffic increase has to be matched mainly by increasing the density of the access networks as well as providing a modest amount of extra spectrum. Thus, the future research challenges are in designing energy-and cost-efficient short-range architectures and systems that support super-dense deployments. A non-technical complication is that such infrastructures are likely to lead to highly fragmented markets with a large number of operators and infrastructure owners.

  • 3121.
    Zander, Jens
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sung, Ki Won
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Maehoenen, Petri
    Petrova, Marina
    Jantti, Riku
    Kronander, Jonas
    On the scalability of cognitive radio:: Assessing the commercial viability of secondary spectrum access2013In: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 20, no 2, 28-35 p.Article in journal (Refereed)
    Abstract [en]

    We report results from the recently finished QUASAR project, which has studied overall system aspects of cognitive radio technologies and has paid attention particularly to the economic viability of different use cases. We find that successful secondary sharing goes far beyond the detection of spectrum holes. Large-scale commercial success requires that secondary systems are scalable so that a large number of users can be served in an economically viable fashion. Our key finding is that secondary spectrum use is not an attractive method for most of the commercially interesting scenarios, from neither a business nor technical perspective. Perhaps somewhat surprisingly, the likely commercial "sweet spot" for secondary sharing in the lower frequency bands is short-range indoor communications. We also find that regulation does not currently present a significant barrier in Europe or the United States.

  • 3122.
    Zandieh, Behdis
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Indoor Wireless Local Area Network (WLAN): Measurement and Modeling from a user perspective2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

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

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

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

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

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

  • 3123.
    Zapolskas, Vytautas
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Securing Cloud Storage Service2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

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

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

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

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

  • 3124.
    Zappone, Alessio
    et al.
    TU Dresden, Dresden, Germany.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Sanguinetti, Luca
    University of Pisa, Italy; CentraleSupelec, France.
    Jorswieck, Eduard
    TU Dresden, Dresden, Germany.
    A Framework for Globally Optimal Energy-Efficient Resource Allocation in Wireless Networks2016Conference paper (Refereed)
  • 3125.
    Zdravkovic, Jelena
    et al.
    KTH, School of Information and Communication Technology (ICT), Computer and Systems Sciences, DSV.
    Zikra, Iyad
    KTH, School of Information and Communication Technology (ICT), Computer and Systems Sciences, DSV.
    Ilayperuma, Tharaka
    An MDA method for service modeling by formalizing REA and open-edi business frameworks with SBVR2011In: 4th IFIP WG 8.1 Working Conference on Method Engineering, ME 2011, 2011, 219-224 p.Conference paper (Refereed)
    Abstract [en]

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

  • 3126.
    Zeadally, Sherali
    et al.
    Univ Dist Columbia, Dept Comp Sci & Informat Technol, Network Syst Lab, Washington, DC 20008 USA..
    Hunt, Ray
    Univ Canterbury, Coll Engn, Dept Comp Sci & Software Engn, Christchurch 1, New Zealand..
    Chen, Yuh-Shyan
    Natl Taipei Univ, Dept Comp Sci & Informat Engn, San Shia, Taipei County, Taiwan..
    Irwin, Angela
    Univ S Australia, Sch Comp & Informat Sci, Mawson Lakes, SA 5095, Australia..
    Hassan, Aamir
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Vehicular ad hoc networks (VANETS): status, results, and challenges2012In: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 50, no 4, 217-241 p.Article in journal (Refereed)
    Abstract [en]

    Recent advances in hardware, software, and communication technologies are enabling the design and implementation of a whole range of different types of networks that are being deployed in various environments. One such network that has received a lot of interest in the last couple of years is the Vehicular Ad-Hoc Network (VANET). VANET has become an active area of research, standardization, and development because it has tremendous potential to improve vehicle and road safety, traffic efficiency, and convenience as well as comfort to both drivers and passengers. Recent research efforts have placed a strong emphasis on novel VANET design architectures and implementations. A lot of VANET research work have focused on specific areas including routing, broadcasting, Quality of Service (QoS), and security. We survey some of the recent research results in these areas. We present a review of wireless access standards for VANETs, and describe some of the recent VANET trials and deployments in the US, Japan, and the European Union. In addition, we also briefly present some of the simulators currently available to VANET researchers for VANET simulations and we assess their benefits and limitations. Finally, we outline some of the VANET research challenges that still need to be addressed to enable the ubiquitous deployment and widespead adoption of scalable, reliable, robust, and secure VANET architectures, protocols, technologies, and services.

  • 3127.
    Zeeck, Simon
    KTH, Superseded Departments, Teleinformatics.
    Cellular Interworking: Handover between WATM and GSM1998Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

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

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

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

    • Layer 2 tunneling is a well-know and proven concept in cellular networks
    • The layer 2 connection can be transparently changed while being mobile.
    • Both QoS and traffic parameters in layer2 (e.g., ATM) can be used
    • The freedom and power of IP on layer 3 for signaling (and for data, of course)
  • 3128.
    Zennaro, Marco
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Bagula, Antoine
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Ntareme, Hervé
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Inggs, Gordon
    Scott, Simon
    On the relevance of open wireless sensors for NGN2009In: International Telecommunication Union - Proceedings of the 2009 ITU-T Kaleidoscope Academic Conference: Innovations for Digital Inclusion, K-IDI 2009, IEEE conference proceedings, 2009, 193-200 p.Conference paper (Refereed)
    Abstract [en]

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

  • 3129.
    Zenteno, Efrain
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences. KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Digital Compensation Techniques for Transmitters in Wireless Communications Networks2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

  • 3130.
    Zenteno, Efrain
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Digital Compensation Techniques for Transmitters inWireless Communications Networks2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

  • 3131.
    Zenteno, Efrain
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Amin, Shoaib
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Isaksson, Magnus
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Combating the Dimensionality of Nonlinear MIMOAmplifier Predistortion by Basis Pursuit2014In: Proceedings of the 44th European Microwave Conference, 2014, 833-836 p.Conference paper (Refereed)
    Abstract [en]

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

  • 3132.
    Zenteno, Efrain
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences. ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Amin, Shoaib
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences. ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Händel, Peter
    ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Combating the Dimensionality of Nonlinear MIMO Amplifier Predistortion by Basis Pursuit2014In: Proceedings of the 44th European Microwave Conference, 2014, 833-836 p.Conference paper (Refereed)
    Abstract [en]

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

  • 3133.
    Zepernick, Hans-Jürgen
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Iqbal, Muhammad Imran
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Quality of Experience of Digital Multimedia Broadcasting Services: An Experimental Study2016In: 2016 IEEE Sixth International Conference on Communications and Electronics (ICCE), IEEE, 2016, 437-442 p.Conference paper (Refereed)
    Abstract [en]

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

  • 3134.
    Zerouali, Mehdi
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    VoIP Communications over WLANs: Implementation of a new downlink transmission protocol2010Report (Other academic)
    Abstract [en]

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

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

  • 3135.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Comparison of angle-spread in outdoor-to-outdoor and outdoor-to-indoor cases in an urban macro-cesll2005In: Wireless Personal Multimedia Communications (WPMC), Aalborg, Denmark, 2005Conference paper (Refereed)
  • 3136.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Method for Decreasing Fading in a Telecommunication System1998Patent (Other (popular science, discussion, etc.))
    Abstract [en]

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

  • 3137. Zetterberg, Per
    Performance of narrow beams in an suburban environment2000In: Vehicular Technology Conferance (VTC 2000-Spring), 2000, 1235-1239 p.Conference paper (Refereed)
  • 3138.
    Zetterberg, Per
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fardi, Ramin
    Open Source SDR Frontend and Measurements for 60-GHz Wireless Experimentation2015In: IEEE Access, E-ISSN 2169-3536, Vol. 3, 445-456 p.Article in journal (Refereed)
    Abstract [en]

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

  • 3139.
    Zetterberg, Per
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jaldén, Niklas
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Investigation of Simple Algorithms for Estimation of Delay-Spread and Angle-Spread2012Report (Other academic)
    Abstract [en]

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

  • 3140.
    Zetterberg, Per
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ottersten, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    The Spectrum Efficiency of a Base Station Antenna Array System for Spatially Selective Transmission1995In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 44, no 3, 651-660 p.Article in journal (Refereed)
    Abstract [en]

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

  • 3141.
    Zhai, Chuanying
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zou, Zhuo
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zheng, Lirong
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Software defined radio IR-UWB positioning platform for RFID and WSN application2012In: Ultra-Wideband (ICUWB), 2012 IEEE International Conference on, IEEE , 2012, 501-505 p.Conference paper (Refereed)
    Abstract [en]

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

  • 3142.
    Zhai, Chuanying
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zou, Zhuo
    KTH, School of Information and Communication Technology (ICT), Industrial and Medical Electronics. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zhou, Qin
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Mao, Jia
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Chen, Qiang
    KTH, School of Information and Communication Technology (ICT), Industrial and Medical Electronics. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Tenhunen, Hannu
    KTH, School of Information and Communication Technology (ICT), Industrial and Medical Electronics. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zheng, Lirong
    KTH, School of Information and Communication Technology (ICT), Industrial and Medical Electronics. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Xu, L.
    A 2.4-GHz ISM RF and UWB hybrid RFID real-time locating system for industrial enterprise Internet of Things2016In: Enterprise Information Systems, ISSN 1751-7575, E-ISSN 1751-7583, 1-18 p.Article in journal (Refereed)
    Abstract [en]

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

  • 3143.
    Zhai, Chuanying
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zou, Zhuo
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zhou, Qin
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Zheng, Lirong
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    A Software Defined Radio platform for passive UWB-RFID localization2012In: 2012 IEEE International Conference on Wireless Information Technology and Systems, ICWITS 2012, IEEE , 2012, 6417741- p.Conference paper (Refereed)
    Abstract [en]

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

  • 3144.
    Zhang, Congcong
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    A Distributed Range Query Framework for Internet of Things2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

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

  • 3145.
    Zhang, Feng
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture.
    Secure Mobile Service-Oriented Architecture2012Doctoral thesis, monograph (Other academic)
    Abstract [en]

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

  • 3146.
    Zhang, Feng
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Kondoro, Aron
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Muftic, Sead
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Location-based authentication and authorization using smart phones2012In: Proc. of the 11th IEEE Int. Conference on Trust, Security and Privacy in Computing and Communications, TrustCom-2012 - 11th IEEE Int. Conference on Ubiquitous Computing and Communications, IUCC-2012, IEEE , 2012, 1285-1292 p.Conference paper (Refereed)
    Abstract [en]

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

  • 3147.
    Zhang, Feng
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Kounelis, Ioannis
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Muftic, Sead
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Generic, secure and modular (GSM) methodology for design and implementation of secure mobile applications2012In: SECURWARE 2012 - 6th International Conference on Emerging Security Information, Systems and Technologies, Rome, Italy: International Academy, Research and Industry Association (IARIA), 2012, 1-6 p.Conference paper (Refereed)
    Abstract [en]

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

  • 3148.
    Zhang, Feng
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Muftic, Sead
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Schmöelzer, Gernot
    Secure Service-Oriented Architecture for Mobile Transactions2011In: World Congress on Internet Security (WorldCIS-2011), London: IEEE Communications Society, 2011, 133-138 p.Conference paper (Refereed)
    Abstract [en]

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

  • 3149. Zhang, Haibo
    et al.
    Österlind, Fredrik
    Soldati, Pablo
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Johansson, Mikael
    Time-optimal convergecast with separated packet copying: Scheduling policies and performance2015In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 64, no 2, 793-803 p.Article in journal (Refereed)
    Abstract [en]

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

  • 3150.
    Zhang, Hao
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    A Peer to Peer Security Protocol for the Internet of Things: Secure Communication for the SensibleThings Platform2014Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

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

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