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  • 1.
    Abad Caballero, Israel Manuel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Secure Mobile Voice over IP2003Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Voice over IP (VoIP) can be defined as the ability to make phone calls and to send faxes (i.e., to do everything we can do today with the Public Switched Telephone Network, PSTN) over IP−based data networks with a suitable quality of service and potentially a superior cost/benefit ratio. There is a desire to provide (VoIP) with the suitable security without effecting the performance of this technology. This becomes even more important when VoIP utilizes wireless technologies as the data networks (such as Wireless Local Area Networks, WLAN), given the bandwidth and other constraints of wireless environments, and the data processing costs of the security mechanisms. As for many other (secure) applications, we should consider the security in Mobile VoIP as a chain, where every link, from the secure establishment to the secure termination of a call, must be secure in order to maintain the security of the entire process.

    This document presents a solution to these issues, providing a secure model for Mobile VoIP that minimizes the processing costs and the bandwidth consumption. This is mainly achieved by making use of high− throughput, low packet expansion security protocols (such as the Secure Real−Time Protocol, SRTP); and high−speed encryption algorithms (such as the Advanced Encryption Standard, AES).

    In the thesis I describe in detail the problem and its alternative solutions. I also describe in detail the selected solution and the protocols and mechanisms this solution utilizes, such as the Transport Layer Security (TLS) for securing the Session Initiation Protocol (SIP), the Real−Time Protocol (RTP) profile Secure Real−Time Protocol (SRTP) for securing the media data transport , and the Multimedia Internet KEYing (MIKEY) as the key−management protocol. Moreover, an implementation of SRTP, called MINIsrtp, is also provided. The oral presentation will provide an overview of these topics, with an in depth examination of those parts which were the most significant or unexpectedly difficult.

    Regarding my implementation, evaluation, and testing of the model, this project in mainly focused on the security for the media stream (SRTP). However, thorough theoretical work has also been performed and will be presented, which includes other aspects, such as the establishment and termination of the call (using SIP) and the key−management protocol (MIKEY).

    Download full text (pdf)
    fulltext
  • 2.
    Abad Camarero, Daniel
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Performance analysis of IPv4 / IPv6 protocols over the third generation mobile network2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Currently, the IPv4 protocol is heavily used by institutions, companies and individuals, but every day there is a higher number of devices connected to the network such as home appliances, mobile phones or tablets. Each machine or device needs to have its own IP address to communicate with other machines connected to Internet. This implies the need for multiple IP addresses for a single user and the current protocol begins to show some deficiencies due to IPv4 address space exhaustion. Therefore, for several years experts have been working on an IP protocol update: the IPv6 128-bit version can address up to about 340 quadrillion system devices concurrently. With IPv6, today, every person on the planet could have millions of devices simultaneously connected to the Internet.

    The choice of the IP protocol version affects the performance of the UMTS mobile network and the browsers as well. The aim of the project is to measure how the IPv6 protocol performs compared to the previous IPv4 protocol. It is expected that the IPv6 protocol generates a smaller amount of signalling and less time is required to fully load a web page. We have analysed some KPIs (IP data, signalling, web load time and battery) in lab environment using Smartphones, to observe the behaviour of both, the network and the device.  The main conclusion of the thesis is that IPv6 really behaves as expected and generates savings in signalling, although the IP data generated is larger due to the size of the headers. However, there is still much work as only the most important webpages and the applications with a high level of market penetration operate well over the IPv6 protocol.

    Download full text (pdf)
    Performance Analysis of IPv4-IPv6 protocols over the Third Generation Mobile Network-Daniel Abad
  • 3.
    Abarghouyi, Hadis
    et al.
    IUST, Iran; MTNi Co, Iran.
    Razavizadeh, S. Mohammad
    IUST, Iran.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    QoE-Aware Beamforming Design for Massive MIMO Heterogeneous Networks2018In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 67, no 9, p. 8315-8323Article in journal (Refereed)
    Abstract [en]

    One of the main goals of the future wireless networks is improving the users quality of experience (QoE). In this paper, we consider the problem of the QoE-based resource allocation in the downlink of a massive multiple-input multiple-output heterogeneous network. The network consists of a macrocell with a number of small cells embedded in it. The small cells base stations (BSs) are equipped with a few antennas, while the macro BS is equipped with a massive number of antennas. We consider the two services Video and Web Browsing and design the beamforming vectors at the BSs. The objective is to maximize the aggregated mean opinion score (MOS) of the users under constraints on the BSs powers and the required quality of service of the users. We also consider extra constraints on the QoE of users to more strongly enforce the QoE in the beamforming design. To reduce the complexity of the optimization problem, we suggest suboptimal and computationally efficient solutions. Our results illustrate that increasing the number of antennas at the BSs and also increasing the number of small cells antennas in the network leads to a higher user satisfaction.

  • 4. Abbas, Q.
    et al.
    Hassan, Syed Ali
    Pervaiz, H.
    Ni, Q.
    A Markovian Model for the Analysis of Age of Information in IoT Networks2021In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 10, no 7, p. 1596-1600, article id 9410556Article in journal (Refereed)
    Abstract [en]

    Age of Information (AoI) is a critical metric in status update systems as these systems require the fresh updates. This letter investigates the uplink of an Internet-of-Thing (IoT) network where L nodes transmit their information packets to a base station. The effects of the arrival rate of packets at the nodes, the number of nodes in the system, and queue length of each node have been studied by devising a discrete time Markov chain (MC) model. This model helps in predicting the values of AoI and probability of packet drops in such systems. The notion of first-in first-out is used for queuing, which transmits the oldest packet first, resulting in decreasing the overall AoI of the system. The results show that AoI increases with the increase in queue length, number of nodes and arrival rate and we quantify the aforementioned metrics using the MC model. The results found using the MC model are also validated using extensive simulations. © 2012 IEEE.

  • 5. Abbas, Q.
    et al.
    Zeb, S.
    Hassan, S. A.
    Age of Information in Backscatter Communication2021In: Internet Things, Springer , 2021, p. 67-80Conference paper (Refereed)
    Abstract [en]

    Age of Information (AoI) has been introduced to characterize the newness of data which is observed in real time. In other words, it is the measure of time elapsed since the generation of last received update about a process and is a vital metric in networks such as Internet of things (IoTs), especially when the application demands fresh updates. Most of the applications require fresh data e.g., applications related to environmental monitoring, smart agriculture, body area networks etc. On the other hand backscatter communication promises to resolve one of the most challenging issues of IoT devices, i.e., making them capable for communication without the batteries. The importance of AoI in backscatter communication is paramount to gauge performance of backscatter IoT networks. This chapter addresses the significance of AoI in backscatter communication and suggests some techniques to design a communication system with minimum AoI, maximum energy efficiency, and minimum outage. © 2021, Springer Nature Switzerland AG.

  • 6. Abbasi, A. G.
    et al.
    Muftic, Sead
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS.
    Schmölzer, Gernot
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS.
    A model and design of a security provider for Java applications2009In: International Conference for Internet Technology and Secured Transactions, ICITST 2009, 2009, p. 5402592-Conference paper (Refereed)
    Abstract [en]

    The model and design of a generic security provider provides a comprehensive set of security services, mechanisms, encapsulation methods, and security protocols for Java applications. The model is structured in four layers; each layer provides services to the upper layer and the top layer provide services to applications. The services reflect security requirements derived from a wide range of applications; from small desktop applications to large distributed enterprise environments. Based on the abstract model, this paper describes design and implementation of an instance of the provider comprising various generic security modules: symmetric key cryptography, asymmetric key cryptography, hashing, encapsulation, certificates management, creation and verification of signatures, and various network security protocols. This paper also describes the properties extensibility, flexibility, abstraction, and compatibility of the Java Security Provider.

  • 7. Abbasi, A. G.
    et al.
    Muftic, Sead
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS.
    Schmölzer, Gernot
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS.
    CryptoNET: A model of generic security provider2010In: International Journal of Internet Technology and Secured Transactions, ISSN 1748-569X, E-ISSN 1748-5703, Vol. 2, no 3-4, p. 321-335Article in journal (Refereed)
    Abstract [en]

    The model and design of a generic security provider provides a comprehensive set of security services, mechanisms, encapsulation methods, and security protocols for Java applications. The model is structured in four layers; each layer provides services to the upper layer and the top layer provide services to applications. The services reflect security requirements derived from a wide range of applications; from small desktop applications to large distributed enterprise environments. Based on the abstract model, this paper describes design and implementation of an instance of the provider comprising various generic security modules: symmetric key cryptography, asymmetric key cryptography, hashing, encapsulation, certificates management, creation and verification of signatures, and various network security protocols. This paper also describes the properties for extensibility, flexibility, abstraction, and compatibility of the Java security provider.

  • 8.
    Abbasi, Shirin
    et al.
    Islamic Azad University, Iran.
    Rahmani, Amir Masoud
    Islamic Azad University, Tehran, Iran; National Yunlin University of Science and Technology, Taiwan.
    Balador, Ali
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Sahafi, Amir
    Islamic Azad University, Iran.
    A fault-tolerant adaptive genetic algorithm for service scheduling in internet of vehicles2023In: Applied Soft Computing, ISSN 1568-4946, E-ISSN 1872-9681, Vol. 143, article id 110413Article in journal (Refereed)
    Abstract [en]

    Over the years, a range of Internet of Vehicles services has emerged, along with improved quality parameters. However, the field still faces several limitations, including resource constraints and the time response requirement. This paper extracts cost, energy, processing power, service management, and resource allocation parameters. Mathematical equations are then defined based on these parameters. To simplify the process complexity and ensure scalability, we propose an algorithm that uses the genetic algorithm for fault and cost management during resource allocation to services. The main concept is to pick resources for services using a genetic algorithm. We discuss the processing and energy costs associated with this function, which is the algorithm's objective function and is created to optimize cost. Our approach goes beyond the conventional genetic algorithm in two stages. In the first step, services are prioritized, and resources are allocated in accordance with those priorities; in the second step, load balancing in message transmission paths is ensured, and message failures are avoided. The algorithm's performance is evaluated using various parameters, and it was shown to outperform other metaheuristic algorithms like the classic genetic algorithm, particle swarm, and mathematical models. Different scenarios with various nodes and service variables are defined in various system states, including fault occurrences to various percentages of 10, 20, and 30. To compare methods, we consider different parameters, the most significant being performance success rate. Moreover, the cost optimization has a good convergence after iterations, and the rate of improvement in the big scenario has slowed down after 150 iterations. Besides, it provides acceptable performance in response time for services.

  • 9.
    Abdalla, Osman
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Health Informatics and Logistics.
    Design and implementation of a signaling system for a novel light-baseed bioprinter: Design och implementering av ett signalsystem för en ny ljusbaserad bioprinter2023Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A 3D bioprinter employing light-based technology has been designed and constructed in an EU-funded research initiative known as BRIGHTER (Bioprinting by Light-Sheet Lithography). This initiative is a collaborative effort between institutions and companies and aims to develop a technique for efficient and accurate production of engineered tissue.

    Presently, the bioprinter’s function is limited to 2D printing, with the lack of 3D printing capabilities. 

    The problem addressed is the integration of two separate electronic systems within the bioprinter to control the laser beam’s trajectory for 3D printing. The goal of the project is to create functional software and simulation tools to control the hardware modules in a precise and synchronized manner, thereby enabling 3D printing.

    The outcome manifests as a software prototype, which successfully facilitates intercommunication between the two electronic subsystems within the bioprinter, thereby enabling further progress on the bioprinter with 3D printing available. Nevertheless, the prototype requires thorough testing to determine its optimal operational efficiency in terms of timing the movements for the various hardware modules.

    Download full text (pdf)
    Bioprinter
  • 10.
    Abd-Elmagid, Mohamed A.
    et al.
    Virginia Tech, VA 24061 USA.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Dhillon, Arpreet S.
    Virginia Tech, VA 24061 USA.
    On the Role of Age of Information in the Internet of Things2019In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 57, no 12, p. 72-77Article in journal (Refereed)
    Abstract [en]

    In this article, we provide an accessible introduction to the emerging idea of Age of Information (AoI) that quantifies freshness of information and explore its possible role in the efficient design of freshness-aware Internet of Things (IoT). We start by summarizing the concept of AoI and its variants with emphasis on the differences between AoI and other well-known performance metrics in the literature, such as throughput and delay. Building on this, we explore freshness-aware IoT design for a network in which IoT devices sense potentially different physical processes and are supposed to frequently update the status of these processes at a destination node (e.g., a cellular base station). Inspired by recent interest, we also assume that these IoT devices are powered by wireless energy transfer by the destination node. For this setting, we investigate the optimal sampling policy that jointly optimizes wireless energy transfer and scheduling of update packet transmissions from IoT devices with the goal of minimizing long-term weighted sum-AoI. Using this, we characterize the achievable AoI region. We also compare this AoI-optimal policy with the one that maximizes average throughput (throughput-optimal policy), and demonstrate the impact of system state on their structures. Several promising directions for future research are also presented.

    Download full text (pdf)
    fulltext
  • 11.
    Abdul Aziz Hasan Ali, Aamir
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Shahzad, Muhammad Adil
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A Joint Subcarrier/Power allocation Scheme for OFDMA-based Cellular Networks2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The assignment of this master thesis consists of initiating power, subcarrier allocation in a dynamic FFR based scheme designed for multi-cell OFDMA networks and to enhance the throughput of all center users in bandwidth hungry borrower cells (overloaded cells) which was previously degraded by original FFR3 scheme as a result of partitioning of system bandwidth into center and edge bands respectively. The method uses band borrowing to compensate center user’s throughput loss in a semi and fully overloaded system. The scheme uses dynamic programming method (0/1 knapsack problem) to bargain an edge band on various power levels and tends to check the best combination (power and sub-carrier) which the system can utilize while still maintaining acceptable throughput loss for the users at the edge of the neighboring cell (lender cell).

    The algorithm consists of generating a borrowing request to neighboring cells for utilizing their edge bands by the overloaded borrower cell if their average center user throughput reaches below a minimum threshold value set in the system. The borrowing method uses 0/1 knapsack problem to capture an edge band based on limiting factors of total cost in average throughput losses by neighbors (Ci) and Un (tolerable mean user edge user throughput loss by lending cell). While solving knapsack problem the lender (neighbors) will check Ci and Un before granting the right to use its edge band. The later stage requires reducing subcarrier power level in order to utilize the lenders edge band using "soft borrower" mode. The borrowed sub-carriers will be activated take power from the original center band sub-carriers of the overloaded cell by taking into account the interference between the lender and the borrower. In case of negative (0) reply from the lender cell after the first request, multiple requests are generated at reduce power level at every step to order to acquire more bands. If a neighbor has band borrowing requests from multiple overloaded base stations, the band will be granted to the one which gives minimal loss in terms of throughput to the lender cell.

    The simulation results are analyzed w.r.t reuse-1 and FFR3 scheme of a multi cell regular and irregular scenarios comprising of lightly to heavily overloaded cells with various subcarrier allocation patterns. An overhead and time assessment is also presented between borrower and lender cells. Simulation results show an increase of 60% in center user’s throughput w.r.t original FFR3 scheme with an acceptable loss of 18% at the edges in complex overloaded scenarios while the overall system throughout increases by 35%.

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    fulltext
  • 12. Abedifar, V.
    et al.
    Furdek, Marija
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Muhammad, Ajmal
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Eshghi, M.
    Wosinska, Lena
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Routing, modulation format, spectrum and core allocation in SDM networks based on programmable filterless nodes2018In: Optics InfoBase Conference Papers, Optics Info Base, Optical Society of America, 2018Conference paper (Refereed)
    Abstract [en]

    An RMSCA approach based on binary particle swarm optimization is proposed for programmable filterless SDM networks, aimed at minimizing core and spectrum usage. Nearoptimal resource consumption.

  • 13. Abedifar, Vahid
    et al.
    Furdek, Marija
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Muhammad, Ajmal
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Eshghi, Mohammad
    Wosinska, Lena
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Routing, Modulation and Spectrum Assignment in Programmable Networks based on Optical White Boxes2018In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 10, no 9, p. 723-735Article in journal (Refereed)
    Abstract [en]

    Elastic optical networks (EONs) can help overcome the flexibility challenges imposed by emerging heterogeneous and bandwidth-intensive applications. Among the different solutions for flexible optical nodes, optical white box switches implemented by architecture on demand (AoD) have the capability to dynamically adapt their architecture and module configuration to the switching and processing requirements of the network traffic. Such adaptability allows for unprecedented flexibility in balancing the number of required nodal components in the network, spectral resource usage, and length of the established paths. To investigate these trade-offs and achieve cost-efficient network operation, we formulate the routing, modulation, and spectrum assignment (RMSA) problem in AoD-based EONs and propose three RMSA strategies aimed at optimizing a particular combination of these performance indicators. The strategies rely on a newly proposed internal node configuration matrix that models the structure of optical white box nodes in the network, thus facilitating hardware-aware routing of connection demands. The proposed strategies are evaluated in terms of the number of required modules and the related cost, spectral resource usage, and average path length. Extensive simulation results show that the proposed RMSA strategies can achieve remarkable cost savings by requiring fewer switching modules than the benchmarking approaches, at a favorable trade-off with spectrum usage and path length.

  • 14.
    Abid, Muhammad Adil
    et al.
    Malmö University, Faculty of Technology and Society (TS), Department of Computer Science and Media Technology (DVMT).
    Amouzad Mahdiraji, Saeid
    Malmö University, Faculty of Technology and Society (TS), Department of Computer Science and Media Technology (DVMT).
    Lorig, Fabian
    Malmö University, Faculty of Technology and Society (TS), Department of Computer Science and Media Technology (DVMT). Malmö University, Internet of Things and People (IOTAP).
    Holmgren, Johan
    Malmö University, Faculty of Technology and Society (TS), Department of Computer Science and Media Technology (DVMT).
    Mihailescu, Radu-Casian
    Malmö University, Faculty of Technology and Society (TS), Department of Computer Science and Media Technology (DVMT).
    Petersson, Jesper
    Department of Health Care Management, Region Skåne, 21428 Malmö, Sweden; Department of Neurology, Lund University, 22242 Malmö, Sweden.
    A Genetic Algorithm for Optimizing Mobile Stroke Unit Deployment2023In: Procedia Computer Science, ISSN 1877-0509, Vol. 225, p. 3536-3545Article in journal (Refereed)
    Abstract [en]

    A mobile stroke unit (MSU) is an advanced ambulance equipped with specialized technology and trained healthcare personnel to provide on-site diagnosis and treatment for stroke patients. Providing efficient access to healthcare (in a viable way) requires optimizing the placement of MSUs. In this study, we propose a time-efficient method based on a genetic algorithm (GA) to find the most suitable ambulance sites for the placement of MSUs (given the number of MSUs and a set of potential sites). We designed an efficient encoding scheme for the input data (the number of MSUs and potential sites) and developed custom selection, crossover, and mutation operators that are tailored according to the characteristics of the MSU allocation problem. We present a case study on the Southern Healthcare Region in Sweden to demonstrate the generality and robustness of our proposed GA method. Particularly, we demonstrate our method's flexibility and adaptability through a series of experiments across multiple settings. For the considered scenario, our proposed method outperforms the exhaustive search method by finding the best locations within 0.16, 1.44, and 10.09 minutes in the deployment of three MSUs, four MSUs, and five MSUs, resulting in 8.75x, 16.36x, and 24.77x faster performance, respectively. Furthermore, we validate the method's robustness by iterating GA multiple times and reporting its average fitness score (performance convergence). In addition, we show the effectiveness of our method by evaluating key hyperparameters, that is, population size, mutation rate, and the number of generations.

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    fulltext
  • 15.
    Aboelwafa, Mariam
    et al.
    American University of Cairo, Egypt.
    Seddik, Karim G.
    American University of Cairo, Egypt.
    Eldefrawy, Mohammed
    Halmstad University, Sweden.
    Gadallah, Yasser
    American University of Cairo, Egypt.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    A Machine Learning-Based Technique for False Data Injection Attacks Detection in Industrial IoT2020In: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 7, no 9, p. 8462-8471Article in journal (Refereed)
    Abstract [en]

    The accelerated move towards the adoption of the industrial Internet of Things (IIoT) paradigm has resulted in numerous shortcomings as far as security is concerned. One of the IIoT affecting critical security threats is what is termed as the ” False Data Injection” (FDI) attack. The FDI attacks aim to mislead the industrial platforms by falsifying their sensor measurements. FDI attacks have successfully overcome the classical threat detection approaches. In this study, we present a novel method of FDI attack detection using Autoencoders (AEs). We exploit the sensor data correlation in time and space, which in turn can help identify the falsified data. Moreover, the falsified data are cleaned using the denoising AEs. Performance evaluation proves the success of our technique in detecting FDI attacks. It also significantly outperforms a support vector machine (SVM) based approach used for the same purpose. The denoising AE data cleaning algorithm is also shown to be very effective in recovering clean data from corrupted (attacked) data.

  • 16.
    Abrahamsson, Henrik
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Ben Abdesslem, Fehmi
    RISE - Research Institutes of Sweden, ICT, SICS.
    Ahlgren, Bengt
    RISE - Research Institutes of Sweden, ICT, SICS.
    Björkman, Mats
    Mälardalen University, Sweden.
    Brunstrom, Anna
    Karlstad University, Sweden.
    Marsh, Ian
    RISE - Research Institutes of Sweden, ICT, SICS.
    Selecting Operator in 3G/4G Networks for Time-Critical C-ITS Applications2018Conference paper (Refereed)
  • 17.
    Abrahamsson, Henrik
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Ben Abdesslem, Fehmi
    RISE - Research Institutes of Sweden, ICT, SICS.
    Ahlgren, Bengt
    RISE - Research Institutes of Sweden, ICT, SICS.
    Brunstrom, Anna
    Karlstad University, Sweden.
    Marsh, Ian
    RISE - Research Institutes of Sweden, ICT, SICS.
    Björkman, Mats
    Mälardalen University, Sweden.
    Connected Vehicles in Cellular Networks: Multi-access versus Single-access Performance2018Conference paper (Refereed)
    Abstract [en]

    Connected vehicles can make roads traffic safer andmore efficient, but require the mobile networks to handle timecriticalapplications. Using the MONROE mobile broadbandmeasurement testbed we conduct a multi-access measurementstudy on buses. The objective is to understand what networkperformance connected vehicles can expect in today’s mobilenetworks, in terms of transaction times and availability. The goalis also to understand to what extent access to several operatorsin parallel can improve communication performance.In our measurement experiments we repeatedly transfer warningmessages from moving buses to a stationary server. Wetriplicate the messages and always perform three transactionsin parallel over three different cellular operators. This creates adataset with which we can compare the operators in an objectiveway and with which we can study the potential for multi-access.In this paper we use the triple-access dataset to evaluate singleaccessselection strategies, where one operator is chosen for eachtransaction. We show that if we have access to three operatorsand for each transaction choose the operator with best accesstechnology and best signal quality then we can significantlyimprove availability and transaction times compared to theindividual operators. The median transaction time improves with6% compared to the best single operator and with 61% comparedto the worst single operator. The 90-percentile transaction timeimproves with 23% compared to the best single operator andwith 65% compared to the worst single operator.

  • 18.
    Abrahamsson, Olle
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Danev, Danyo
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Structural Balance Considerations for Networks with Preference Orders as Node Attributes2022In: 2022 56TH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS, AND COMPUTERS, IEEE , 2022, p. 1255-1261Conference paper (Refereed)
    Abstract [en]

    We discuss possible definitions of structural balance conditions in a network with preference orderings as node attributes. The main result is that for the case with three alternatives (A, B, C) we reduce the (3!)(3) = 216 possible configurations of triangles to 10 equivalence classes, and use these as measures of balance of a triangle towards possible extensions of structural balance theory. Moreover, we derive a general formula for the number of equivalent classes for preferences on n alternatives. Finally, we analyze a real-world data set and compare its empirical distribution of triangle equivalence classes to a null hypothesis in which preferences are randomly assigned to the nodes.

  • 19.
    Abramson, Norman
    et al.
    Department of Electrical Engineering, University of Hawaii, USA.
    Sacchi, Claudio
    Information Engineering and Computer Science Department, University of Trento, Italy.
    Bellalta, Boris
    Department of Information and Communication Technologies, Universitat Pompeu Fabra, Spain.
    Vinel, Alexey
    Saint-Petersburg Institute for Informatics and Automation, Russian Academy of Sciences, Russia.
    Multiple access communications in future-generation wireless networks2012In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, p. Art nr 45-Article in journal (Refereed)
  • 20. Abrardo, A
    et al.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Tola, B.
    Network coding schemes for Device-To-Device communications based relaying for cellular coverage extension2015In: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC, 2015, p. 670-674Conference paper (Refereed)
    Abstract [en]

    In this paper, we study the performance of device-To-device (D2D) based range extension in terms of sum rate and power efficiency when a relaying user equipment (UE) helps to improve the coverage for cell-edge UEs. In our design, the relaying UE has own traffic to transmit and receive to/from the cellular base station (BS) and can operate either in amplify-And-forward (AF) or decode-And-forward (DF) modes and can make use of either digital or analogue (PHY layer) network coding. In this rather general setting, we propose mode selection, resource allocation and power control schemes and study their performance by means of system simulations. We find that the performance of the DF scheme with network coding is superior both to the traditional cellular and the AF based relaying schemes, including AF with two-slot or three-slot PHY layer network coding.

  • 21.
    Abrardo, Andrea
    et al.
    Univ Siena, Dipartimento Ingn Informaz, I-53100 Siena, Italy. brardo, Andrea; Moretti, Marco.
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Moretti, Marco
    Distributed Digital and Hybrid Beamforming Schemes With MMSE-SIC Receivers for the MIMO Interference Channel2019In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 68, no 7, p. 6790-6804Article in journal (Refereed)
    Abstract [en]

    This paper addresses the problem of weighted sumrate maximization and mean squared error (MSE) minimization for the multiple-input multiple-output (MIMO) interference channel. Specifically, we consider a weighted minimum MSE architecture where each receiver employs successive interference cancellation (SIC) to separate the various received data streams and derive a hybrid beamforming scheme, where the transmitters operate with a number of radio frequency chains smaller than the number of antennas, particularly suited for millimeter-wave channels and 5G applications. To derive our proposed schemes, we first study the relationship between sum-rate maximization and weighted MSE minimization when using SIC receivers, assuming fully digital beamforming. Next, we consider the important-and, as it turns out, highly non-trivial-case where the transmitters employ hybrid digital/analog beamforming, developing a distributed joint hybrid precoding and SIC-based combining algorithm. Moreover, for practical implementation, we propose a signaling scheme that utilizes a common broadcast channel and facilitates the acquisition of channel state information, assuming minimal assistance from a central node such as a cellular base station. Numerical results show that both the proposed weighted MMSE-SIC schemes exhibit great advantages with respect to their linear counterparts in terms of complexity, feedback information, and performance.

  • 22.
    Abrardo, Andrea
    et al.
    Univ Siena, Dipartimento Ingn Informaz, I-53100 Siena, Italy..
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Moretti, Marco
    Univ Pisa, Dipartimento Ingn Informaz, I-50126 Pisa, Italy..
    Telek, Miklos
    Budapest Univ Technol & Econ, Dept Networked Syst & Serv, H-1117 Budapest, Hungary.;MTA BME Informat Syst Res Grp, H-1117 Budapest, Hungary..
    MMSE Receiver Design and SINR Calculation in MU-MIMO Systems With Imperfect CSI2019In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 8, no 1, p. 269-272Article in journal (Refereed)
    Abstract [en]

    The performance of the uplink of multiuser multiple input multiple output systems depends critically on the receiver architecture and on the quality of the acquired channel state information. A popular approach is to design linear receivers that minimize the mean squared error (MSE) of the received data symbols. Unfortunately, most of the literature does not take into account the presence of channel state information errors in the MSE minimization. In this letter we develop a linear minimum MSE (MMSE) receiver that employs the noisy instantaneous channel estimates to minimize the MSE, and highlight the dependence of the receiver performance on the pilot-to-data power ratio. By invoking the theory of random matrices, we calculate the users' signal-to-interference-plus-noise ratio as a function of the number of antennas and the pilot-to-data power ratio of all users. Numerical results indicate that this new linear receiver outperforms the classical mismatched MMSE receiver.

  • 23.
    Abrardo, Andrea
    et al.
    University of Siena, Italy.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control. Ericsson Research, Stockholm.
    Tola, Besmir
    University of Siena, Italy.
    Network Coding Schemes for Device-to-Device Communications Based Relaying for Cellular Coverage Extension2015Report (Other academic)
    Abstract [en]

    Although network assisted device-to-device (D2D) communications is known to improve the spectraland energy efficiency of proximal communications, its performance is less understood when employedto extend the coverage of cellular networks.In this paper, we study the performance of D2D basedrange extension in terms of sum rate and power efficiency when a relaying user equipment (UE) helps to improvethe coverage for cell-edge UEs.In our design, the relaying UE has own traffic to transmit and receive to/from the cellular base station (BS) andcan operate either in amplify-and-forward (AF) or decode-and-forward (DF) modes and can make use of either digital oranalogue (PHY layer) network coding.In this rather general setting, we propose mode selection, resource allocation and power control schemesand study their performance by means of system simulations.We find that the performance of the DF scheme with network coding is superior both to the traditional cellularand the AF based relaying schemes, including AF with two-slot or three-slot PHY layer network coding.

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  • 24.
    Abusubaih, Murad
    et al.
    Technische Universit¨at Berlin.
    Gross, James
    Technische Universit¨at Berlin.
    Wolisz, Adam
    Technische Universit¨at Berlin.
    An Inter-Access Point Coordination Protocol for Dynamic Channel Selection in IEEE802.11 Wireless LANs2007Conference paper (Refereed)
    Abstract [en]

    This paper presents and evaluates an Inter-Access Point Coordination protocol for dynamic channel selection in IEEE 802.11 WLANs. It addresses an open issue for the implementation of many distributed and centralized dynamic channel selection policies proposed to mitigate interference problems in Wireless LANs (WLANs). The presented protocol provides services to a wide range of policies that require different levels of coordination among APs by enabling them to actively communicate and exchange information. An Intra-Cell protocol that enables interaction between the AP and its accommodated stations to handle channel switching within the same cell is also presented.

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  • 25.
    Achilleos, Achilleas
    et al.
    Frederick University, Cyprus.
    Mettouris, Christos
    University of Cyprus, Cyprus.
    Yeratziotis, Alexandros
    University of Cyprus, Cyprus.
    Papadopoulos, George
    University of Cyprus, Cyprus.
    Pllana, Sabri
    Linnaeus University, Faculty of Technology, Department of computer science and media technology (CM).
    Huber, Florian
    SYNYO GmbH, Austria.
    Jäger, Bernhard
    SYNYO GmbH, Austria.
    Leitner, Peter
    SYNYO GmbH, Austria.
    Ocsovszky, Zsófia
    BioTalentum Ltd, Hungary.
    Dinnyés, András
    BioTalentum Ltd, Hungary.
    SciChallenge: A Social Media Aware Platform for Contest-Based STEM Education and Motivation of Young Students2019In: IEEE Transactions on Learning Technologies, E-ISSN 1939-1382, Vol. 12, no 1, p. 98-111Article in journal (Refereed)
    Abstract [en]

    Scientific and technological innovations have become increasingly important as we face the benefits and challenges of both globalization and a knowledge-based economy. Still, enrolment rates in STEM degrees are low in many European countries and consequently there is a lack of adequately educated workforce in industries. We believe that this can be mainly attributed to pedagogical issues, such as the lack of engaging hands-on activities utilized for science and math education in middle and high schools. In this paper, we report our work in the SciChallenge European project, which aims at increasing the interest of pre-university students in STEM disciplines, through its distinguishing feature, the systematic use of social media for providing and evaluation of the student-generated content. A social media-aware contest and platform were thus developed and tested in a pan-European contest that attracted >700 participants. The statistical analysis and results revealed that the platform and contest positively influenced participants STEM learning and motivation, while only the gender factor for the younger study group appeared to affect the outcomes (confidence level – p<.05).

  • 26.
    Adamsson, Maximilian
    et al.
    Mälardalen University, School of Business, Society and Engineering.
    Enehöjd, Pontus
    Mälardalen University, School of Business, Society and Engineering.
    Ledarskap - Nu på Digital nivå: En studie om hur digital kommunikation bör utformas för att organisationer ska bli mer effektiva och ha ett bra kommunikationsflöde med mindre informationsbortfall.2020Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Digital kommunikation är idag självklart för de allra flesta människor, alla kommunicerar digitalt via olika sorters enheter och kanaler. Dock kommer den digitala kommunikationen i väldigt många olika former så kan det ibland bli svårt och komplext för alla att hantera denna sorts kommunikation. Denna studie har för avsikt att skapa ett underlag för en mer komplett och kontrollerbar kommunikation via digitala medel, samt hur ledarskap kan främjas via kommunikation i digital form. Detta ska bidra med en grundläggande kunskap kring hur en organisation bör hantera och förmedla sin information och kommunikation via digitala medel.

    Studien fokuserar på att skapa en förståelse för hur digital kommunikation upplevs av mottagaren. För att därifrån kunna se hur denna upplevelse kan föras närmare den fysiska kommunikationen mellan en ledare och medarbetare. I ett samarbete med Barn och utbildningsförvaltningen, en väldigt stor organisation med ansvar för all grundutbildning i Eskilstuna kommun, det vill säga allt från förskola upp till gymnasial utbildning. Denna organisation har analyserats genom en induktiv forskningsmetod med kvalitativa intervjuer, dessa har varit grunden för att samla in data. Genom dessa kvalitativa intervjuer samlas åsikter och tankar in från medlemmar av alla olika delar av organisationen för att skapa en heltäckande bild om hur den digitala kommunikationen upplevs och fungerar.

    Kunskapsbidragets syfte för denna uppsats var att få fram kunskap om hur en digital kommunikationsmiljö bör utformas för att organisationer ska bli mer effektiva, ha ett bra kommunikationsflöde samt mindre informationsbortfall. Detta syfte anses vara uppfyllt genom slutsatserna utifrån teori och empiriinsamling. Där en organisation med en bra struktur, organisationskunskap samt grundtanke har alla möjligheter att då utveckla sina ledare. Detta kan i sin tur utveckla medarbetare och därmed skapa en mer effektiv organisation, med bra och tydliga kanaler där alla är införstådda hur dem fungerar.

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  • 27.
    Adamsson, Stina
    Linnaeus University, Faculty of Technology, Department of Informatics.
    Kommunikationskanaler vid intern nyhetsspridning: En fallstudie om hur kommunikationskanaler påverkar den upplevda kommunikationseffektiviteten vid nyhetsspridning2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Communication is an important function within organizations and the ways of communicating have developed rapidly due to technological development, which can make it difficult to know which communication channel that is best to use in different situations. This report is based on a case study were the perceived communication efficiency tended to vary depending on which communication channel that was used. Previous research shows how the choice of communication channels can affect the communication efficiency, however, it does not show this from the perspective of news as an information type. Therefore, it was considered interesting to study how different communication channels affect the communication efficiency in terms of news distribution.

     

    The aim of this study was to illustrate and describe how communication channels affect the perceived communication efficiency when the information that is transferred consists of news. To achieve this, the following research question would be answered:

     

    • What advantages and disadvantages do employees experience with communication channels regarding the communication efficiency for news distribution in a large national company?

     

    Theories that have been applied in the study are Media Richness Theory and Osgood and Schramms circular communication model. Theories have been used to explain how news distribution takes place in the case company and to illustrate and possibly explain the problems that the company experience with news distribution.

     

    Data was collected by applying a qualitative method in which semi-structured interviews have been used. The result shows that respondents experience both advantages and disadvantages with all the communication channels and that the perceived communication efficiency tended to vary depending on which kind of news. When the result was set against the research question and the theoretical framework, advantages and disadvantages that were experienced, turned out to be depending on if the news were routine or non-routine and how it was matched with a rich or poor communication channel, which Media Richness Theory also declare. 

     

    The conclusion of this study shows that news distribution through face to face and telephone enables direct interaction and transmission of emotions, however, emotions are not transmitted as well through telephone as face to face. The many signals can also be experienced as overwhelmingly. E-mail, intranet and signboard are effective in terms of time and are not as depending on time and space. In addition, the possibility of direct interaction and transmission of feelings is limited. The result indicates that advantages and disadvantages with the communication channels seems to be linked to whether the channel is perceived as suitable to transfer different kinds of news. Rich communication channels are perceived to be effective for transmitting non-routine news and poor channels are perceived to be effective for transmitting routine news.

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  • 28.
    Adewole, Kayode Sakariyah
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Department of Computer Science and Media Technology, Malmö University, Malmö, Sweden; Department of Computer Science, University of Ilorin, Ilorin, Nigeria.
    Torra, Vicenç
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Department of Computer Science and Media Technology, Malmö University, Malmö, Sweden.
    Privacy protection of synthetic smart grid data simulated via generative adversarial networks2023In: Proceedings of the 20th international conference on security and cryptography, SECRYPT 2023 / [ed] DiVimercati, SD; Samarati, P, SciTePress, 2023, p. 279-286Conference paper (Refereed)
    Abstract [en]

    The development in smart meter technology has made grid operations more efficient based on fine-grained electricity usage data generated at different levels of time granularity. Consequently, machine learning algorithms have benefited from these data to produce useful models for important grid operations. Although machine learning algorithms need historical data to improve predictive performance, these data are not readily available for public utilization due to privacy issues. The existing smart grid data simulation frameworks generate grid data with implicit privacy concerns since the data are simulated from a few real energy consumptions that are publicly available. This paper addresses two issues in smart grid. First, it assesses the level of privacy violation with the individual household appliances based on synthetic household aggregate loads consumption. Second, based on the findings, it proposes two privacy-preserving mechanisms to reduce this risk. Three inference attacks are simulated and the results obtained confirm the efficacy of the proposed privacy-preserving mechanisms.

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  • 29.
    Adigozalov, Niyaz
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    The Intelligent Use of Multiple Interfaces: Using multiplexing to reduce the overhead for small packets2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Long-Term Evolution (LTE) is the latest development in wide area cellular mobile network technology. In contrast with the earlier generations of circuit-switched mobile networks, LTE is all-IP packet-switched network. Both voice and data are sent inside IP packets. Voice over IP (VoIP) is used to provide voice service to LTE users. The speech frames are encapsulated into real-time protocol (RTP) packets and sent over the network. The underlying UDP and IP layers prepend their headers to this small RTP packet resulting in a relatively high overhead. The small size of the RTP packets containing voice/audio leads to an overhead problem as the protocol overhead is in addition to the large LTE frame overhead, thus wasting network resources. This master’s thesis project proposes to multiplex RTP and data packets at the user’s device as a solution to reduce the overhead. Moreover, the capability of modern user devices to switch between several interfaces (such as LTE and WLAN), is taken into account and the multiplexing of multiple traffic flows or a single traffic flow are studied in the case of a vertical handover. Performance and cost metrics are used to evaluate different potential demultiplexing points, and then the best possible demultiplexing point is identified. The results of this evaluation show that several demultiplexing points can be used based on the operator’s needs. The increased packet payload size increases the energy efficiency of LTE and may avoid the need of the UE to switch to WLAN to save power. In addition, to ensure high quality of service for VoIP traffic, the simultaneous use of multiple interfaces is efficient if the multiplexer is enabled. The multiplexing solution proposed by this thesis is also fully compatible with any virtual private network encapsulation protocol.

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  • 30.
    Aeddula, Omsri
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Flyborg, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Larsson, Tobias
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Anderberg, Peter
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Sanmartin Berglund, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Renvert, Stefan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health. Kristianstad University, SWE.
    A Solution with Bluetooth Low Energy Technology to Support Oral Healthcare Decisions for improving Oral Hygiene2021In: ACM International Conference Proceeding Series, Association for Computing Machinery (ACM), 2021, Vol. 1, p. 134-139Conference paper (Refereed)
    Abstract [en]

    The advent of powered toothbrushes and associated mobile health applications provides an opportunity to collect and monitor the data, however collecting reliable and standardized data from large populations has been associated with efforts from the participants and researchers. Finding a way to collect data autonomously and without the need for cooperation imparts the potential to build large knowledge banks. A solution with Bluetooth low energy technology is designed to pair a powered toothbrush with a single-core processor to collect raw data in a real-time scenario, eliminating the manual transfer of powered toothbrush data with mobile health applications. Associating powered toothbrush with a single-core processor is believed to provide reliable and comprehensible data of toothbrush use and propensities can be a guide to improve individual exhortation and general plans on oral hygiene quantifies that can prompt improved oral wellbeing. The method makes a case for an expanded chance to plan assistant capacities to protect or improve factors that influence oral wellbeing in individuals with mild cognitive impairment. The proposed framework assists with determining various parameters, which makes it adaptable and conceivable to execute in various oral care contexts 

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  • 31.
    af Sandeberg, Joakim
    KTH, School of Information and Communication Technology (ICT).
    Graphical system visualization and flow display: A visual representation of an authentication, authorization, and accounting backend2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Displaying the architecture of a software system is not a simple task. Showing all of the available information will unnecessarily complicate the view, while showing too little might render the view unhelpful. Furthermore, showing the dynamics of the operation of such a system is even more challenging.

    This thesis project describes the development of a graphical tool that can both display the configuration of an advanced authentication, authorization, and accounting (AAA) system and the messages passed between nodes in the system.  The solution described uses force-based graph layouts coupled with adaptive filters as well as vector-based rendering to deliver a view of the status of the system. Force-based layout spreads out the nodes in an adaptive fashion. The adaptive filters starts by showing what is most often the most relevant information, but can be configured by the user. Finally, the vector based rendering offers unlimited zoom into the individual nodes in the graph in order to display additional detailed information.

    Unified Modeling Language (UML) sequence charts are used to display the message flow inside the system (both between nodes and inside individual nodes).

    To validate the results of this thesis project each iteration of the design was evaluated through meetings with the staff at Aptilo Networks. These meetings provided feedback on the direction the project was taking as well as provided input (such as ideas for features to implement).

    The result of this thesis project shows a way to display the status of an AAA system with multiple properties displayed at the same time. It combines this with a view of the flow of messages and application of policies in the network via a dynamically generated UML sequence diagram. As a result human operators are able to see both the system’s architecture and the dynamics of its operation using the same user interface. This integrated view should enable more effective management of the AAA system and facilitate responding to problems and attacks.

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  • 32.
    Af Ugglas, Mikael
    KTH, Superseded Departments (pre-2005), Teleinformatics.
    Accounting Management on a DTM Network1999Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Large investments are currently being made for the infrastructure of voice and data services. The network providers’ revenues consist of fees from the users of the network. Until today it has been difficult to charge for the actual usage, instead so-called flat rate charging has been applied.

    Dynamic synchronous Transfer Mode (DTM) is a circuit switched technique that is designed to meet the requirements of future multimedia services. This includes support for real time applications and high throughput. Physically separated channels, whose capacity can easily be adjusted to the users’ demands, provide the service. The channels and their guaranteed service make DTM a very interesting technique when it comes to charging for network usage, as the characteristics of the channel can be easily described by relatively few parameters.

    This thesis describes how accounting management can be applied on a DTM network. It identifies the parameters that need to be collected and describes how to gather these parameters into call data records (CDRs). Furthermore, it outlines how the transportation of the CDRs to the network providers’ billing system can be performed.

  • 33.
    Aftab, Muhammad Usman
    et al.
    National University of Sciences and Technology, Pakistan.
    Hussain, Mehdi
    National University of Sciences and Technology, Pakistan.
    Lindgren, Anders
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Ghafoor, Abdul
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Towards A Distributed Ledger Based Verifiable Trusted Protocol for VANET2021In: 2021 International Conference on Digital Futures and Transformative Technologies, ICoDT2 2021, Institute of Electrical and Electronics Engineers Inc. , 2021Conference paper (Refereed)
    Abstract [en]

    To ensure traffic safety and proper operation of vehicular networks, safety messages or beacons are periodically broadcasted in Vehicular Adhoc Networks (VANETs) to neighboring nodes and road side units (RSU). Thus, authenticity and integrity of received messages along with the trust in source nodes is crucial and highly required in applications where a failure can result in life-threatening situations. Several digital signature based approaches have been described in literature to achieve the authenticity of these messages. In these schemes, scenarios having high level of vehicle density are handled by RSU where aggregated signature verification is done. However, most of these schemes are centralized and PKI based where our goal is to develop a decentralized dynamic system. Along with authenticity and integrity, trust management plays an important role in VANETs which enables ways for secure and verified communication. A number of trust management models have been proposed but it is still an ongoing matter of interest, similarly authentication which is a vital security service to have during communication is not mostly present in the literature work related to trust management systems. This paper proposes a secure and publicly verifiable communication scheme for VANET which achieves source authentication, message authentication, non repudiation, integrity and public verifiability. All of these are achieved through digital signatures, Hash Message Authentication Code (HMAC) technique and logging mechanism which is aided by blockchain technology.

  • 34. Agarwal, D.
    et al.
    Gionis, Aristides
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Theoretical Computer Science, TCS.
    Simperl, E.
    Foreword from the Programme Chairs2022In: 31st ACM World Wide Web Conference, WWW 2022, Association for Computing Machinery, Inc , 2022Conference paper (Refereed)
  • 35.
    Agnoletto, Daniel
    et al.
    Institute of Informatics, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
    Jonsson, Magnus
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Pignaton de Freitas, Edison
    Institute of Informatics, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
    Time slot transmission scheme with packet prioritization for Bluetooth low energy devices used in real-time applications2020In: International Journal of Wireless Information Networks, ISSN 1068-9605, E-ISSN 1572-8129, Vol. 27, no 4, p. 518-534Article in journal (Refereed)
    Abstract [en]

    Bluetooth Low Energy (BLE) is one of the most important technologies that feed the growing field of Internet of Things and Wireless Sensor Networks. Due to its flexibility and unique low power-consumption, an increasing number of industrial devices, household appliances and wearables are being designed using it. However, the real-time demands of these networks such as timing and Quality of Service are not fully covered by the protocol itself. To help improve and offer some control over these characteristics, this paper presents a time slot transmission scheme with packet prioritization. It is based on the division and allocation of the connection interval to two types of messages: real-time and ordinary. The goal is to offer the lowest packet loss and time guarantees for real-time messages, while providing acceptable throughput for ordinary ones. Since the probability of a BLE connection to close increases with the number of packets sent through it, the position where a real-time packet is being sent as well as the number of ordinary messages in a connection represent key factors. The use of the first and last slot for real-time packets with ordinary flow restricted to the space between them decreases the transmission delay uncertainty and allows probability tuning based on the number of ordinary messages. Simulations were performed using the proposed scheme and a reduction of more than 100 times in the delay variance was observed for real-time transmissions. Regarding reliability, around 5% of the packets were lost for a bit error rate of 10−3. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

  • 36.
    Aguilar, Antonio
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    A Patient Identification System using RFID and IEEE 802.11b Wireless Networks2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The recent increased focus on patient safety in hospitals has yielded a flood of new technologies and tools seeking to improve the quality of patient care at the point of care. Hospitals are complex institutions by nature, and are constantly challenged to improve the quality of healthcare delivered to patients while trying to reduce the rate of medical errors and improve patient safety. Here a simple mistake such as patient misidentification, specimen misidentification, wrong medication, or wrong blood transfusion can cause the loss of a patient’s life. Misidentification of patients is a common problem that many hospitals face on the daily basis. Patient misidentification is one of the leading causes of medical errors and medical malpractice in hospitals and it has been recognised as a serious risk to patient safety.

    Recent studies have shown that an increasing number of medical errors are primarily caused by adverse drug events which are caused directly or indirectly by incorrect patient identification. In recognition of the increasing threat to patient safety, it is important for hospitals to prevent these medical errors from happening by adopting a suitable patient identification system that can improve upon current safety procedures.

    The focus of this master’s thesis is the design, implementation, and evaluation of a handheld-based patient identification system that uses radio frequency identification (RFID) and IEEE 802.11b wireless local area networks to identify patients. In this solution, each patient is given a RFID wristband which contains demographic information (patient ID number, ward number, hospital code, etc.) of the patient. A handheld device equipped with IEEE 802.11b wireless local area network connectivity and a RFID reader is then used by the medical staff to read the patient’s wristband, identify the patient, and access the relevant records of this patient.

    This work was carried out at the Department of Medical Physics and Bioengineering at the University College Hospital Galway (UCHG), Ireland and the National University of Ireland, Galway.

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  • 37.
    Aguilar, Antonio
    et al.
    Digital Enterprise Research Institute, National University of Ireland, Galway, Ireland.
    van der Putten, Wil
    Department of Medical Physics, University College Hospital Galway, Galway, Ireland .
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Positive Patient Identification using RFID and Wireless  Networks2006In: Proceedings of the HISI 11th Annual Conference and Scientific Symposium, Dublin, Ireland, Dublin, Ireland, 2006Conference paper (Refereed)
    Abstract [en]

    The increased focus on patient safety in hospitals has yielded a flood of new technologies and tools seeking to improve the quality of patient care at the point-of-care. Hospitals are complex institutions by nature, and are constantly challenged to improve the quality of healthcare delivered to patients while trying to reduce the rate of medical errors and improve patient safety. Here a simple mistake such as patient misidentification, specimen misidentification, wrong medication, or wrong blood transfusion can cause the loss of a patient's life. The focus of this paper is the implementation and evaluation of a handheld-based patient identification system that uses radio frequency identification (RFID) and 802.11b wireless networks to identify patients. In this approach, each patient is given a RFID wristband which contains demographic information (patient ID number, patient summary, hospital code) of the patient. A handheld device equipped with 802.11b wireless connectivity and a RFID reader is then used by the medical staff to read the patient's wristband and identify the patient. This work was carried out at the Department of Medical Physics and Bioengineering at the University College Hospital Galway, Ireland and in co-operation with the National University of Ireland, Galway.

  • 38.
    Ahani, Ghafour
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computing Science.
    Optimal Scheduling for Timely Information in Communication Systems2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The explosive growth of data in information society poses significant challenges in the timely delivery of information in the context of communication networks. Hence, optimal utilization of scarce network resources is crucial. This dissertation contributes to several aspects related to the timely delivery of information, including scheduling of data flows between sources and destinations in a network, scheduling of content caching in a base station of mobile networks, and scheduling of information collection. Two important metrics, namely, delivery deadline and information freshness, are accounted for. Mathematical models and tailored solution approaches are developed via tools from optimization.

    Five research papers are included in the dissertation. Paper I studies a flow routing and scheduling problem with delivery deadline. This type of problem arises in many applications such as data exchange in scientific projects or data replication in data centers where large amounts of data need to be timely distributed across the globe. Papers II, III, and IV inves­tigate content caching along time in a base station. Content caching at the network’s edge has recently been considered a cost­efficient way of providing users with their requested informa­tion. In Paper II, the schedule for updating the cache is optimized with respect to the content requests of users and the popularity of contents over time. Paper III, as an extension of Paper II, addresses the question of how to keep the cache information fresh, as all contents can not be up­dated due to the limited capacity of the backhaul link. The freshness of information is quantified via the notion of age of information (AoI). Paper IV investigates joint optimization of content caching as well as recommendation; the latter contributes to satisfying content requests in case of a cache miss. Paper V studies optimal scheduling of information collection from a set of sensor nodes via an unmanned aerial vehicle. The objective is to keep the overall AoI as small as possible.

    In these studies, analysis of problem complexity is provided, and time­efficient solution al­gorithms based on column generation, Lagrangian decomposition, and graph labeling are de­veloped. The algorithms also yield a bound of global optimum, that can be used to assess the performance of any given solution. The effectiveness of the algorithms in obtaining near­optimal solutions is demonstrated via extensive simulations.

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  • 39.
    Ahani, Ghafour
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Wiatr, Pawel
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Routing and scheduling of network flows with deadlines and discrete capacity allocation2020In: Networks, ISSN 0028-3045, E-ISSN 1097-0037, Vol. 76, no 1, p. 54-74Article in journal (Refereed)
    Abstract [en]

    Joint scheduling and routing of data flows with deadline constraints in communication networks has been attracting research interest. This type of problem distinguishes from conventional multicommodity flows due to the presence of the time dimension. In this paper, we address a flow routing and scheduling problem with delivery deadline, where the assignment of link capacity occurs in discrete units. Discrete capacity allocation is motivated by applications in communication systems, where it is common to have a base unit of capacity (e.g., wavelength channel in optical communications). We present and prove complexity results of the problem. Next, we give an optimization formulation based on a time slicing approach, which amounts to a discretization of the time into time slices to enable to formulate the deadline constraints. We then derive an effective reformulation of the problem, via which a column generation algorithm is developed. In addition, we propose a simple and fast max-flow-based algorithm. We use a number of networks and traffic scenarios to study various performance aspects of the algorithms.

  • 40.
    Ahani, Ghafour
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computing Science. Komar Univ Sci & Technol, Dept Comp Sci, Sulaymaniyah 75105, Iraq.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computing Science.
    Optimal Content Caching and Recommendation With Age of Information2024In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 23, no 1, p. 689-704Article in journal (Refereed)
    Abstract [en]

    Content caching at the network edge is an effective way of mitigating backhaul load and improving user experience. Caching efficiency can be enhanced by content recommendation and by keeping the information fresh. By content recommendation, a requested content that is not in the cache can be alternatively satisfied by a related cached content recommended by the system. Information freshness can be quantified by age of information (AoI). This article has the following contributions. First, we address optimal scheduling of cache updates for a time-slotted system accounting for content recommendation and AoI, and to the best of our knowledge, there is no work that has jointly taken into account these aspects. Next, we rigorously prove the problem's NP-hardness. Then, we derive an integer linear formulation, by which the optimal solution can be obtained for small-scale scenarios. On the algorithmic side, our contributions include the development of an effective algorithm based on Lagrangian decomposition, and efficient algorithms for solving the resulting subproblems. Our algorithm computes a bound that can be used to evaluate the performance of any suboptimal solution. We conduct simulations to show the effectiveness of our algorithm.

  • 41. Ahani, Ghafour
    et al.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology.
    Optimal Scheduling of Content Caching with recommendation and Freshness of InformationIn: Article in journal (Refereed)
    Abstract [en]

    Content caching at the network edge has been considered an effective way of mitigating backhaul load and improving user experience. Caching efficiency can be enhanced by content recommendation and by keeping the information as fresh as possible. To the best of our knowledge, there is no work that jointly takes into account both these aspects in content caching. By content recommendation, a requested content that is not in the cache can be alternatively satisfied by a related cached content recommended by the system. Informationfreshness, arising naturally in content caching can be quantified by age of information (AoI). We address, optimal scheduling of cache updates for a time-slotted system accounting for both content recommendation and AoI, subject to cache capacity as well as backhaul capacity for updating the cache. For each content, there are requests that need to be satisfied and there is a cost function capturing the freshness of information which is monotonically increasing in the AoI. We present the following contributions. First, we prove that the problem is NP-hard even with contents of uniform size. Second, we derive an integer linear formulation for the problem, by which the optimal solution can be obtained for small-scale scenarios. Third, we develop an algorithm based on Lagrangian decomposition. Fourth, we develop efficient algorithms for solving the resulting subproblems. In addition, our algorithm computes a bound that can be used to evaluate the performance of any suboptimal solution. Finally, we conduct simulations to show the effectiveness of our algorithm in comparison to a greedy schedule.

  • 42.
    Ahani, Ghafour
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computing Science.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computing Science.
    Sun, Sumei
    Institute for Infocomm Research, Singapore, Singapore;Singapore Institute of Technology, Singapore, Singapore.
    Optimal Scheduling of Age-centric Caching: Tractability and Computation2022In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 21, p. 2939-2954Article in journal (Refereed)
    Abstract [en]

    The notion of age of information (AoI) has become an important performance metric in network and control systems. Information freshness, represented by AoI, naturally arises in the context of caching. We address optimal scheduling of cache updates for a time-slotted system where the contents vary in size. There is limited capacity for the cache for making updates. Each content is associated with a utility function that depends on the AoI and the time duration of absence from the cache. For this combinatorial optimization problem, we present the following contributions. First, we provide theoretical results of problem tractability. Whereas the problem is NP-hard, we prove solution tractability in polynomial time for a special case with uniform content size, by a reformulation using network flows. Second, we derive an integer linear formulation for the problem, of which the optimal solution can be obtained for small-scale scenarios. Next, via a mathematical reformulation, we derive a scalable optimization algorithm using repeated column generation. In addition, the algorithm computes a bound of global optimum, that can be used to assess the performance of any scheduling solution. Performance evaluation of large-scale scenarios demonstrates the strengths of the algorithm in comparison to a greedy schedule. Finally, we extend the applicability of our work to cyclic scheduling.

  • 43.
    Ahani, Ghafour
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Zhao, Yixin
    Nanjing Univ Sci & Technol, Sch Automat, Nanjing 210094, Peoples R China..
    Age-Optimal UAV Scheduling for Data Collection With Battery Recharging2021In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 25, no 4, p. 1254-1258Article in journal (Refereed)
    Abstract [en]

    We study route scheduling of a UAV for data collection from sensor nodes (SNs) with battery recharging. The freshness of the collected information is captured by the metric of age of information (AoI). The objective is to minimize the average AoI cost of all SNs over a scheduling time horizon. We prove that the problem in its general form is NP-hard. Then, for a special case of the problem, we prove that optimum can be computed in polynomial time. Next, we develop an algorithm based on graph labeling. Finally, we show the effectiveness of our algorithm in comparison to greedy scheduling.

  • 44.
    Ahgren, Per
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology.
    Jakobsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology.
    A study of doubletalk detection performance in the presence of acoustic echo path changes2006In: IEEE transactions on consumer electronics, ISSN 0098-3063, E-ISSN 1558-4127, Vol. 52, no 2, p. 515-522Article in journal (Refereed)
    Abstract [en]

    An efficient and well-performing double-talk detection (DTD) algorithm is a vital part of a practically working acoustic echo canceller. However, recent algorithms are typically evaluated using a static time-invariant room acoustic impulse response, omitting a proper treatment of the case when the acoustic path is changing. In this work, we introduce a common framework to objectively evaluate how path changes affect the DTD performance. Via extensive numerical simulations, we conclude that the main factor in acoustic path changes affecting the DTD performance for some of the more common DTD algorithms is variations in the damping of the acoustic path.

  • 45.
    Ahlgren, Bengt
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Grinnemo, Karl-Johan
    Karlstad University, Sweden.
    Abrahamsson, Henrik
    RISE - Research Institutes of Sweden, ICT, SICS.
    Brunstrom, Anna
    Karlstad University, Sweden.
    Hurtig, Per
    Karlstad University, Sweden.
    Latency-aware Multipath Scheduling in Information-centric Networks2019In: Proceedings of the 15th Swedish National Computer Networking Workshop (SNCNW), 2019Conference paper (Other academic)
    Abstract [en]

    We present the latency-aware multipath scheduler ZQTRTT that takes advantage of the multipath opportunities in information-centric networking. The goal of the scheduler is to use the (single) lowest latency path for transaction-oriented flows, and use multiple paths for bulk data flows. A new estimator called zero queue time ratio is used for scheduling over multiple paths. The objective is to distribute the flow over the paths so that the zero queue time ratio is equal on the paths, that is, so that each path is ‘pushed’ equally hard by the flow without creating unwanted queueing. We make an initial evaluation using simulation that shows that the scheduler meets our objectives.

  • 46. Ahlgren, Bengt
    et al.
    Hidell, Markus
    Ngai, Edith C.-H.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Internet of Things for smart cities: Interoperability and open data2016In: IEEE Internet Computing, ISSN 1089-7801, E-ISSN 1941-0131, Vol. 20, no 6, p. 52-56Article in journal (Refereed)
  • 47.
    Ahlin, Lars
    et al.
    FOI.
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT).
    Ben Slimane, Slimane
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Principles of Wireless Communications2006Book (Refereed)
    Abstract [en]

    This textbook provides the reader with a basic understanding of the design and analysis of wireless and mobile communication systems. It deals with the most important techniques, models and tools used today in the design of mobile wireless links and gives an introduction to the design of wireless networks. Topics covered include: fundamentals of radio propagation and antennas; transmission schemes, including modulation, coding and equalising schemes for broadband wireless communications; diversity systems; wireless data transmission; introduction to Wireless Network design and resource management. The fundamentals are illustrated by examples from state-of-the-art technologies such as OFDM, WCDMA, WLANs and others. The book contains a significant number of worked examples and more than 160 problems with answers. It is intended for use in a first graduate course in wireless communications and the reader should be familiar with the fundamentals of probability and communication theory.

  • 48.
    Ahlström, Christer
    et al.
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Swedish Natl Rd & Transport Res Inst, S-58195 Linkoping, Sweden.
    Diederichs, Frederik
    Fraunhofer Inst Optron, Germany.
    Teichmann, Daniel
    Univ Southern Denmark, Denmark; MIT, MA 02139 USA.
    Technologies for Risk Mitigation and Support of Impaired Drivers2022In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 23, no 5, p. 4736-4738Article in journal (Other academic)
    Abstract [en]

    This editorial serves as an extended introduction to the Special Issue on Technologies for Risk Mitigation and Support of Impaired Drivers. It gives the context to recent advances in assisted and automated driving and the new challenges that arise when modern technology meets human users. The Special Issue focuses on the development of robust sensors and detection algorithms for driver state monitoring of fatigue, stress, and inattention, and on the development of personalized multimodal, user-oriented, and adaptive information, warning, actuation, and handover strategies. A summary of more recent developments serves as a motivation for each article that follows.

    Download full text (pdf)
    fulltext
  • 49.
    Ahlström, Christer
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, The Human in the Transport system.. Linköping University, Sweden.
    Diederichs, Frederik
    Fraunhofer Gesellschaft, Germany..
    Teichmann, Daniel
    University of Southern Denmark, Denmark.; MIT, USA..
    Technologies for Risk Mitigation and Support of Impaired Drivers2022In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 23, no 5, p. 4736-4738Article in journal (Other academic)
    Abstract [en]

    This editorial serves as an extended introduction to the Special Issue on Technologies for Risk Mitigation and Support of Impaired Drivers. It gives the context to recent advances in assisted and automated driving and the new challenges that arise when modern technology meets human users. The Special Issue focuses on the development of robust sensors and detection algorithms for driver state monitoring of fatigue, stress, and inattention, and on the development of personalized multimodal, user-oriented, and adaptive information, warning, actuation, and handover strategies. A summary of more recent developments serves as a motivation for each article that follows.

  • 50.
    Ahmad, Aftab
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Performance of MLSE over Fading Channels2013Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    This work examines the performance of a wireless transceiver system. The environment is indoor channelsimulated by Rayleigh and Rician fading channels. The modulation scheme implemented is GMSK inthe transmitter. In the receiver the Viterbi MLSE is implemented to cancel noise and interference dueto the ltering and the channel. The BER against the SNR is analyzed in this thesis. The waterfallcurves are compared for two data rates of 1 M bps and 2 Mbps over both the Rayleigh and Rician fadingchannels.

    Download full text (pdf)
    Thesis
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