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  • 301.
    Bjurefors, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för datorteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Measurements in opportunistic networks2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Opportunistic networks are a subset of delay tolerant networks where the contacts are unscheduled. Such networks can be formed ad hoc by wireless devices, such as mobile phones and laptops. In this work we use a data-centric architecture for opportunistic networks to evaluate data dissemination overhead, congestion in nodes' buffer, and the impact of transfer ordering. Dissemination brings an overhead since data is replicated to be spread in the network and overhead leads to congestion, i.e., overloaded buffers.

    We develop and implement an emulation testbed to experimentally evaluate properties of opportunistic networks. We evaluate the repeatability of experiments in the emulated testbed that is based on virtual computers. We show that the timing variations are on the order of milliseconds.

    The testbed was used to investigate overhead in data dissemination, congestion avoidance, and transfer ordering in opportunistic networks. We show that the overhead can be reduced by informing other nodes in the network about what data a node is carrying. Congestion avoidance was evaluated in terms of buffer management, since that is the available tool in an opportunistic network, to handle congestion. It was shown that replication information of data objects in the buffer yields the best results. We show that in a data-centric architecture were each data item is valued differently, transfer ordering is important to achieve delivery of the most valued data.

  • 302.
    Bjurefors, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för datorteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Opportunistic Networking: Congestion, Transfer Ordering and Resilience2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Opportunistic networks are constructed by devices carried by people and vehicles. The devices use short range radio to communicate. Since the network is mobile and often sparse in terms of node contacts, nodes store messages in their buffers, carrying them, and forwarding them upon node encounters. This form of communication leads to a set of challenging issues that we investigate: congestion, transfer ordering, and resilience.

    Congestion occurs in opportunistic networks when a node's buffers becomes full. To be able to receive new messages, old messages have to be evicted. We show that buffer eviction strategies based on replication statistics perform better than strategies that evict messages based on the content of the message.

    We show that transfer ordering has a significant impact on the dissemination of messages during time limited contacts. We find that transfer strategies satisfying global requests yield a higher delivery ratio but a longer delay for the most requested data compared to satisfying the neighboring node's requests.

    Finally, we assess the resilience of opportunistic networks by simulating different types of attacks. Instead of enumerating all possible attack combinations, which would lead to exhaustive evaluations, we introduce a method that use heuristics to approximate the extreme outcomes an attack can have. The method yields a lower and upper bound for the evaluated metric over the different realizations of the attack. We show that some types of attacks are harder to predict the outcome of and other attacks may vary in the impact of the attack due to the properties of the attack, the forwarding protocol, and the mobility pattern.

  • 303.
    Bjurefors, Fredrik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Karaliopoulos, Markourios
    Rohner, Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Smith, Paul
    Theodoropoulos, George
    Gunningberg, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Resilience and Opportunistic Forwarding: Beyond Average Value Analysis2014Ingår i: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 48, nr SI, 111-120 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Opportunistic networks are systems with highly distributed operation, relying on the altruistic cooperation of highly heterogeneous, and not always software and hardware-compatible, user nodes. Moreover, the absence of central coordination and control makes them vulnerable to malicious attacks. In this paper, we study the resilience of popular forwarding protocols to a representative set of challenges to their normal operation. These include jamming locally disturbing message transfer between nodes, hardware/software failures and incompatibility among nodes rendering contact opportunities useless, and free-riding phenomena. We first formulate and promote the metric envelope concept as a tool for assessing the resilience of opportunistic forwarding schemes. Metric envelopes depart from the standard practice of average value analysis and explicitly account for the differentiated challenge impact due to node heterogeneity (device capabilities, mobility) and attackers’ intelligence. We then propose heuristics to generate worst- and best-case challenge realization scenarios and approximate the lower and upper bounds of the metric envelopes. Finally, we demonstrate the methodology in assessing the resilience of three popular forwarding protocols in the presence of the three challenges, and under a comprehensive range of mobility patterns. The metric envelope approach provides better insights into the level of protection path diversity and message replication provide against different challenges, and enables more informed choices in opportunistic forwarding when network resilience becomes important.

  • 304.
    Bjurefors, Fredrik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Karaliopoulos, Merkourios
    Rohner, Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Smith, Paul
    Theodoropoulos, George
    Gunningberg, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Resilience and Opportunistic Forwarding: Beyond Average Value Analysis2013Ingår i: CHANTS '13 Proceedings of the 8th ACM MobiCom workshop on Challenged networks, 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Opportunistic networks are systems with highly distributed operation, relying on the altruistic cooperation of heterogeneous, and not always software- and hardware-compatible user nodes. Moreover, the absence of central control makes them vulnerable to malicious attacks. In this paper, we take a fresh look at the resilience of opportunistic forwarding to these challenges. In particular, we introduce and promote the use of metric envelopes as a resilience assessment tool. Metric envelopes depart from the standard practice of average value analysis and explicitly account for the differentiated impact that a challenge may have on the forwarding performance due to node heterogeneity (device capabilities, mobility) and attackers’ intelligence. The use of metric envelopes is demonstrated in the case of three challenges: jamming, hardware/software failures and incompatibilities, and free-riding phenomena. For each challenge, we first devise heuristics to generate worst- and best-case realization scenarios that can approximate the metric envelopes. Then we derive the envelopes of common performance metrics for three popular forwarding protocols under a comprehensive range of mobility patterns. The metric envelope approach enables more informed choices in opportunistic forwarding whenever network resilience considerations become important. 

  • 305.
    Bjurén, Johan
    Högskolan i Skövde, Institutionen för informationsteknologi.
    USING CASE-BASED REASONING FOR PREDICTING ENERGY USAGE2013Självständigt arbete på avancerad nivå (masterexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this study, the inability to in a future meet the electricity demand and the urge to change the consumption behavior considered. In a smart grid context there are several possible ways to do this. Means include ways to increase the consumer’s awareness, add energy storages or build smarter homes which can control the appliances. To be able to implement these, indications on how the future consumption will be could be useful. Therefore we look further into how a framework for short-term consumption predictions can be created using electricity consumption data in relation to external factors. To do this a literature study is made to see what kind of methods that are relevant and which qualities is interesting to look at in order to choose a good prediction method. Case Based Reasoning seemed to be able to be suitable method. This method was examined further and built using relational databases. After this the method was tested and evaluated using datasets and evaluation methods CV, MBE and MAPE, which have previously been used in the domain of consumption prediction. The result was compared to the results of the winning methods in the ASHRAE competition. The CBR method was expected to perform better than what it did, and still not as good as the winning methods from the ASHRAE competition. The result showed that the CBR method can be used as a predictor and has potential to make good energy consumption predictions. and there is room for improvement in future studies.

  • 306.
    Björklund, Daniel
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Implementation of a Software-Defined Radio Transceiver on High-Speed Digitizer/Generator SDR142012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis describes the specification, design and implementation of a software-defined radio system on a two-channel 14-bit digitizer/generator. The multi-stage interpolations and decimations which are required to operate two analog-to-digital converters at 800 megasamples per second (MSps) and two digital-to-analog converters at 1600 MSps from a 25 MSps software-side interface, were designed and implemented. Quadrature processing was used throughout the system, and a combination of fine-tunable low-rate mixers and coarse high-rate mixers were implemented to allow frequency translation across the entire first Nyquist band of the converters. Various reconstruction filter designs for the transmitter side were investigated and a cheap implementation was done through the use of programmable base-band filters and polynomial approximation.

  • 307.
    Björklund, Fredrik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Karlström, Elin
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Enabling Testing of Lateral Active Safety Functions in a Multi-rate Hardware in the Loop Environment2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    As the development of vehicles moves towards shorter development time, new ways of verifying the vehicle performance is needed in order to begin the verification process at an earlier stage. A great extent of this development regards active safety, which is a collection name for systems that help both avoid accidents and minimize the effects of a collision, e.g brake assist and steering control systems. Development of these active safety functions requires extensive testing and verification in order to guarantee the performance of the functions in different situations. One way of testing these functions is to include them in a Hardware in the Loop simulation, where the involved hardware from the real vehicle are included in the simulation loop.

    This master thesis investigates the possibility to test lateral active safety functions in a hardware in the loop simulation environment consisting of multiple subsystems working on different frequencies. The subsystems are all dependent of the output from other subsystems, forming an algebraic loop between them. Simulation using multiple hardware and subsystems working on different frequencies introduces latency in the simulation. The effect of the latency is investigated and proposed solutions are presented. In order to enable testing of lateral active safety functions, a steering model which enables the servo motor to steer the vehicle is integrated in the simulation environment and validated.

  • 308.
    Björklund, Svante
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Grahn, Per
    Nelander, Anders
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Measurement of Rank and Other Properties of Direct and Scattered Signals2016Ingår i: International Journal of Antennas and Propagation, ISSN 1687-5869, E-ISSN 1687-5877, Vol. 2016, 5483547Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have designed an experiment for low-cost indoor measurements of rank and other properties of direct and scattered signals with radar interference suppression in mind. The signal rank is important also in many other applications, for example, DOA (Direction of Arrival) estimation, estimation of the number of and location of transmitters in electronic warfare, and increasing the capacity in wireless communications. In real radar applications, such measurements can be very expensive, for example, involving airborne radars with array antennas. We have performed the measurements in an anechoic chamber with several transmitters, a receiving array antenna, and a moving reflector. Our experiment takes several aspects into account: transmitted signals with different correlation, decorrelation of the signals during the acquisition interval, covariance matrix estimation, noise eigenvalue spread, calibration, near-field compensation, scattering in a rough surface, and good control of the influencing factors. With our measurements we have observed rank, DOA spectrum, and eigenpatterns of direct and scattered signals. The agreement of our measured properties with theoretic and simulated results in the literature shows that our experiment is realistic and sound. The detailed description of our experiment could serve as help for conducting other well-controlled experiments. © Copyright 2016 Svante Björklund et al.

  • 309.
    Björklund, Ulf
    KTH, Tidigare Institutioner, Teleinformatik.
    Understanding the Performance of the Linux IPv6 Implementation1998Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The new version of the Internet protocol, IP version 6, will eventually replace the current version IP version 4. Before that change can take place the different implementations of IPv6 must be able to perform at least as well as their predecessors, The implementation that is considered here is that of the Linux operating system. All measurements considers native IPv6, e.g. no tunneling in IPv4 packets.

    A small network of two computers was set up on which the performance tests were performed. Throughput and response times were measured on both Ethernet and Fast Ethernet. The conclusions are that IPv6 performs almost as well as IPv4 in both cases. IPv4's slight advantage is due to the fact that it has less overhead on the network since the header is smaller.

    Later a connection to the 6bone is setup. It is run on an ATM network. The performance across that network is also tested.

  • 310.
    Björkman, Anders
    KTH, Tidigare Institutioner, Teleinformatik.
    Configuration of IPv4 Hosts in Zero-Configuration Networks2000Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Zero-configuration networks are networks that require no/zero manual configuration or administration to operate. The essence of a zero-configuration network is that it can be used without having to think about the network at all. The most basic zero-configuration network just provides network communication but more advanced services can be provided as long as no configuration is needed. An important area of use is networks for homes and small businesses. Many of the devices that we have in our homes are or will in a near future be ‘networked’ i.e. capable of network communication. Examples are computers and computer equipment such as printers and scanners, the next generation home-appliances such as the refrigerator and the washing machine, the TV, the stereo, climate sensors etc. etc. The main driving forces for this development are the need for resource sharing e.g. of printers or Internet access, home automation and devices, applications or services that use network communication. Networks for the home must be ‘automatic’ because the average person today has problems programming his VCR and cannot be expected to configure or administrate his/her home-network. Today’s solutions are insufficient because they require manual configuration and some technical knowledge. The market potential is enormous. Almost all homes and most small businesses lack a network infrastructure and many will in a near future acquire it.

    In this thesis I discuss the need and areas of use for zero-configuration networks and I look at how to configure IP hosts in general. Solutions on configuration of hosts in zero-configuration networks are discussed and I propose a solution for IPv4 hosts that enables link-local communication, the most basic type of network communication using IP.

    This master’s thesis was carried out at Ericsson Research in Kista during the fall of 1999 and spring of 2000.

  • 311.
    Björkman Höglund, Matilda
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Olsson, Maria
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    The future of e-commerce2017Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    E-handeln växer eftersom allt fler personer handlar via internet. Konsumtionsmönstret ändras och allt fler söker sig till företags hemsidor för att köpa varor online. Även tjänster som exempelvis musik och film blir mer internetbaserat och köps och beställs ofta via internet. Nu kan nästan vad som helst köpas online, allt från mat till kläder och elektronik. E-handeln är ett smidigare och ibland billigare komplement till den traditionella handeln. Detta underlättar för kunderna och kan frigöra mer tid till de personer som e-handlar. Med den ökade e-handeln uppstår det också problem. Det behövs bra distributionsupplägg som kan ta hand om alla varor som ska transporteras. Den ökade e-handeln innebär fler transporter i städerna. Om e-handeln fortsätter att öka och det blir ännu fler transporter, vilka konsekvenser får det? Vilka olika distributionsupplägg kommer det att finnas i framtiden för att kunna leverera varor till kunderna på ett effektivt sätt? I det här examensarbetet har klädbranschen och dess e-handel undersökts. Det som har studerats, är hur branschen påverkar transporterna kopplat till e-handeln. Intervjuer med olika företag har genomförts i examensarbetet för att få en överblick över hur deras e-handel har utvecklats över tid samt hur de tror att e-handeln kommer att se ut i framtiden. Intervjuer med teoretiker som arbetar med citylogistik har även gjorts, för att få information hur de tror e-handeln kommer påverka transporterna kopplat till e-handeln. I framtiden kommer det troligtvis inte användas några nya distributionsupplägg, utan de som redan finns kommer bli mer utvecklade. De distributionsupplägg som finns idag är att kunderna hämtar sina varor via ett ombud, i en butik/lagerlokal, paketombud eller att varorna skickas hem till kunden. I framtiden kan det bli allt vanligare med hemleverans och att kunderna eventuellt kommer att få styra sina leveranser mer än vad som är möjligt idag. För att se konsekvenserna av transporterna kopplat till e-handeln presenteras två olika fall. Dessa två fall delas upp i åtta olika scenarier. Dessa scenarier är uppbyggda efter olika antaganden om vilka transportmedel som används och i vilken utsträckning. Det scenario som gav lägst koldioxidutsläpp och lägst fordonskilometer var det scenario där 100 % av godset levereras till ett utlämningsställe via en samlastningscentral utan att kunderna använder sin personbil mer. En förändrad volym av e-handel ger olika konsekvenser på transporterna, beroende på vilken typ av distributionsupplägg som används och vilket transportmedel som utnyttjas, samt vilken systemavgränsning som görs. Generellt sett tyder det på att antalet transportkilometer kopplat till e-handeln kommer att öka i framtiden. Vad gäller koldioxidutsläppen är det svårare att göra en bedömning, beroende på vilka transportmedel som kommer att användas i framtiden men också på den tekniska utvecklingen av dessa. Även om antalet fordonskilometer ökar kan effektivare transporter leda till minskade koldioxidutsläpp.

  • 312.
    Björnson, Emil
    KTH Royal Institute Technology, Sweden; Supelec, France.
    Kountouris, Marios
    CentraleSupelec, France.
    Debbah, Merouane
    CentraleSupelec, France.
    Massive MIMO Systems with Non-Ideal Hardware: Energy Efficiency, Estimation, and Capacity Limits2014Ingår i: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 60, nr 11, 7112-7139 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of large-scale antenna arrays can bring substantial improvements in energy and/or spectral efficiency to wireless systems due to the greatly improved spatial resolution and array gain. Recent works in the field of massive multiple-input multiple-output (MIMO) show that the user channels decorrelate when the number of antennas at the base stations (BSs) increases, thus strong signal gains are achievable with little interuser interference. Since these results rely on asymptotics, it is important to investigate whether the conventional system models are reasonable in this asymptotic regime. This paper considers a new system model that incorporates general transceiver hardwareimpairments at both the BSs (equipped with large antenna arrays) and the single-antenna user equipments (UEs). As opposed to the conventional case of ideal hardware, we show that hardwareimpairments create finite ceilings on the channel estimation accuracy and on the downlink/uplink capacity of each UE. Surprisingly, the capacity is mainly limited by the hardware at the UE, while the impact of impairments in the large-scale arrays vanishes asymptotically and interuser interference (in particular, pilot contamination) becomes negligible. Furthermore, we prove that the huge degrees of freedom offered by massive MIMO can be used to reduce the transmit power and/or to tolerate larger hardware impairments, which allows for the use of inexpensive and energy-efficient antenna elements.

  • 313.
    Björnson, Emil
    KTH Royal Institute Technology, Sweden; Supelec, France.
    Debbah, Merouane
    CentraleSupelec, France.
    Ottersten, Björn
    KTH Royal Institute of Technology.
    Multi-Objective Signal Processing Optimization: The Way to Balance Conflicting Metrics in 5G Systems2014Ingår i: IEEE signal processing magazine (Print), ISSN 1053-5888, E-ISSN 1558-0792, Vol. 31, nr 6, 14-23 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The evolution of cellular networks is driven by the dream of ubiquitous wireless connectivity: any data service is instantly accessible everywhere. With each generation of cellular networks, we have moved closer to this wireless dream; first by delivering wireless access to voice communications, then by providing wireless data services, and recently by delivering a Wi-Fi-like experience with wide-area coverage and user mobility management. The support for high data rates has been the main objective in recent years [1], as seen from the academic focus on sum-rate optimization and the efforts from standardization bodies to meet the peak rate requirements specified in IMT-Advanced. In contrast, a variety of metrics/objectives are put forward in the technological preparations for fifth-generation (5G) networks: higher peak rates, improved coverage with uniform user experience, higher reliability and lower latency, better energy efficiency (EE), lower-cost user devices and services, better scalability with number of devices, etc. These multiple objectives are coupled, often in a conflicting manner such that improvements in one objective lead to degradation in the other objectives. Hence, the design of future networks calls for new optimization tools that properly handle the existence of multiple objectives and tradeoffs between them.

  • 314.
    Björnson, Emil
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. Dept. of Electrical Engineering, Linkoping University, Sweden.
    Bengtsson, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Optimal Multiuser Transmit Beamforming: A Difficult Problem with a Simple Solution Structure2014Ingår i: IEEE signal processing magazine (Print), ISSN 1053-5888, E-ISSN 1558-0792, Vol. 31, nr 4, 142-148 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Transmit beamforming is a versatile technique for signal transmission from an array of antennas to one or multiple users [1]. In wireless communications, the goal is to increase the signal power at the intended user and reduce interference to nonintended users. A high signal power is achieved by transmitting the same data signal from all antennas but with different amplitudes and phases, such that the signal components add coherently at the user. Low interference is accomplished by making the signal components add destructively at nonintended users. This corresponds mathematically to designing beamforming vectors (that describe the amplitudes and phases) to have large inner products with the vectors describing the intended channels and small inner products with nonintended user channels.

  • 315.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    de Carvalho, Elisabeth
    Aalborg University, Denmark.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Popovski, Petar
    Aalborg University, Denmark.
    Random Access Protocol for Massive MIMO: Strongest-User Collision Resolution (SUCR)2016Ingår i: 2016 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2016, 820-825 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wireless networks with many antennas at the base stations and multiplexing of many users, known as Massive MIMO systems, are key to handle the rapid growth of data traffic. As the number of users increases, the random access in contemporary networks will be flooded by user collisions. In this paper, we propose a reengineered random access protocol, coined strongest-user collision resolution (SUCR). It exploits the channel hardening feature of Massive MIMO channels to enable each user to detect collisions, determine how strong the contenders channels are, and only keep transmitting if it has the strongest channel gain. The proposed SUCR protocol can quickly and distributively resolve the vast majority of all pilot collisions.

  • 316.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    de Carvalho, Elisabeth
    Aalborg University, Denmark.
    Sorensen, Jesper H.
    Aalborg University, Denmark.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Popovski, Petar
    Aalborg University, Denmark.
    A Random Access Protocol for Pilot Allocation in Crowded Massive MIMO Systems2017Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, nr 4, 2220-2234 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The massive multiple-input multiple-output (MIMO) technology has great potential to manage the rapid growth of wireless data traffic. Massive MIMO achieves tremendous spectral efficiency by spatial multiplexing many tens of user equipments (UEs). These gains are only achieved in practice if many more UEs can connect efficiently to the network than today. As the number of UEs increases, while each UE intermittently accesses the network, the random access functionality becomes essential to share the limited number of pilots among the UEs. In this paper, we revisit the random access problem in the Massive MIMO context and develop a reengineered protocol, termed strongest-user collision resolution (SUCRe). An accessing UE asks for a dedicated pilot by sending an uncoordinated random access pilot, with a risk that other UEs send the same pilot. The favorable propagation of massive MIMO channels is utilized to enable distributed collision detection at each UE, thereby determining the strength of the contenders signals and deciding to repeat the pilot if the UE judges that its signal at the receiver is the strongest. The SUCRe protocol resolves the vast majority of all pilot collisions in crowded urban scenarios and continues to admit UEs efficiently in overloaded networks.

  • 317.
    Björnson, Emil
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jorswieck, Eduard
    Dresden University of Technology, Communications Theory, Communications Laboratory, Dresden, Germany.
    Optimal Resource Allocation in Coordinated Multi-Cell Systems2013Bok (Refereegranskat)
    Abstract [en]

    The use of multiple antennas at base stations is a key component in the design of cellular communication systems that can meet high-capacity demands in the downlink. Under ideal conditions, the gain of employing multiple antennas is well-recognized: the data throughput increases linearly with the number of transmit antennas if the spatial dimension is utilized to serve many users in parallel. The practical performance of multi-cell systems is, however, limited by a variety of nonidealities, such as insufficient channel knowledge, high computational complexity, heterogeneous user conditions, limited backhaul capacity, transceiver impairments, and the constrained level of coordination between base stations.

    This tutorial presents a general framework for modeling different multi-cell scenarios, including clustered joint transmission, coordinated beamforming, interference channels, cognitive radio, and spectrum sharing between operators. The framework enables joint analysis and insights that are both scenario independent and dependent.

    The performance of multi-cell systems depends on the resource allocation; that is, how the time, power, frequency, and spatial resources are divided among users. A comprehensive characterization of resource allocation problem categories is provided, along with the signal processing algorithms that solve them. The inherent difficulties are revealed: (a) the overwhelming spatial degrees-of-freedom created by the multitude of transmit antennas; and (b) the fundamental tradeoff between maximizing aggregate system throughput and maintaining user fairness. The tutorial provides a pragmatic foundation for resource allocation where the system utility metric can be selected to achieve practical feasibility. The structure of optimal resource allocation is also derived, in terms of beamforming parameterizations and optimal operating points.

    This tutorial provides a solid ground and understanding for optimization of practical multi-cell systems, including the impact of the nonidealities mentioned above. The Matlab code is available online for some of the examples and algorithms in this tutorial.

    Note: The supplementary Matlab Code is available at http://dx.doi.org/10.1561/0100000069_supp

  • 318.
    Björnson, Emil
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. Alcatel-Lucent Chair on Flexible Radio, Supélec, France.
    Jorswieck, Eduard
    Dresden University of Technology, Communications Theory, Communications Laboratory, Dresden, Germany.
    Optimal Resource Allocation in Coordinated Multi-Cell Systems: Matlab Code2013Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This is the documentation of the Matlab code supplement to the monograph "Optimal Resource Allocation in Coordinated Multi-Cell Systems" by Emil Björnson and Eduard Jorswieck; see [1] for the full publication details.

    This documentation is distributed along with the code package mentioned above. The package contains Matlab implementations of many of the algorithms described in [1]. The use of these algorithms is exemplified by Matlab scripts (m-files) that generate some of the figures shown in the monograph. The algorithms are briefly described in Section 5 and the selected example figures are described and shown in Section 6. Please note that the all channel vectors are generated randomly as Rayleigh fading in these examples, thus this code package is not able to reproduce exactly the same curves as was shown in the monograph.

  • 319.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Three Practical Aspects of Massive MIMO: Intermittent User Activity, Pilot Synchronism, and Asymmetric Deployment2015Ingår i: 2015 IEEE Globecom Workshops (GC Wkshps), Institute of Electrical and Electronics Engineers (IEEE), 2015, 1-6 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper considers three aspects of Massive MIMO (multiple- input multiple-output) communication networks that have received little attention in previous works, but are important to understand when designing and implementing this promising wireless technology. First, we analyze how bursty data traffic behaviors affect the system. Using a probabilistic model for intermittent user activity, we show that the spectral efficiency (SE) scales gracefully with reduced user activity. Then, we make an analytic comparison between synchronous and asynchronous pilot signaling, and prove that the choice between these has no impact on the SE. Finally, we provide an analytical and numerical study of the SE achieved with random network deployment.

  • 320.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Debbah, Merouane
    CentraleSupelec, France.
    Optimizing Multi-Cell Massive MIMO for Spectral Efficiency: How Many Users Should Be Scheduled?2014Ingår i: 2014 IEEE Global Conference on Signal and Information Processing, GlobalSIP 2014, Institute of Electrical and Electronics Engineers (IEEE), 2014, 612-616 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Massive MIMO is a promising technique to increase the spectral efficiency of cellular networks, by deploying antenna arrays with hundreds or thousands of active elements at the base stations and performing coherent beamforming. A common rule-of-thumb is that these systems should have an order of magnitude more antennas, N, than scheduled users, K, because the users' channels are then likely to be quasi-orthogonal. However, it has not been proved that this rule-of-thumb actually maximizes the spectral efficiency. In this paper, we analyze how the optimal number of scheduled users, K*, depends on N and other system parameters. The value of K* in the large-N regime is derived in closed form, while simulations are used to show what happens at finite N, in different interference scenarios, and for different beamforming.

  • 321.
    Björnson, Emil
    et al.
    KTH Royal Institute Technology, Sweden; Supelec, France.
    Matthaiou, Michail
    Chalmers, Sweden; Queens University of Belfast, North Ireland.
    Debbah, Merouane
    CentraleSupelec, France.
    Massive MIMO with Non-Ideal Arbitrary Arrays: Hardware Scaling Laws and Circuit-Aware Design2015Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 14, nr 8, 4353-4368 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Massive multiple-input multiple-output (MIMO) systems are cellular networks where the base stations (BSs) are equipped with unconventionally many antennas, deployed on co-located or distributed arrays. Huge spatial degrees-of-freedom are achieved by coherent processing over these massive arrays, which provide strong signal gains, resilience to imperfect channel knowledge, and low interference. This comes at the price of more infrastructure; the hardware cost and circuit power consumption scale linearly/affinely with the number of BS antennas N  . Hence, the key to cost-efficient deployment of large arrays is low-cost antenna branches with low circuit power, in contrast to today's conventional expensive and power-hungry BS antenna branches. Such low-cost transceivers are prone to hardware imperfections, but it has been conjectured that the huge degrees-of-freedom would bring robustness to such imperfections. We prove this claim for a generalized uplink system with multiplicative phase-drifts, additive distortion noise, and noise amplification. Specifically, we derive closed-form expressions for the user rates and a scaling law that shows how fast the hardware imperfections can increase with N  while maintaining high rates. The connection between this scaling law and the power consumption of different transceiver circuits is rigorously exemplified. This reveals that one can make the circuit power increase as N − −  √   , instead of linearly, by careful circuit-aware system design

  • 322.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Matthaiou, Michail
    Chalmers, Sweden; Queens University of Belfast, North Ireland.
    Pitarokoilis, Antonios
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Distributed Massive MIMO in Cellular Networks: Impact of Imperfect Hardware and Number of Oscillators2015Ingår i: 23rd European Signal Processing Conference, EUSIPCO 2015, Institute of Electrical and Electronics Engineers (IEEE), 2015, 2436-2440 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Distributed massive multiple-input multiple-output (MIMO) combines the array gain of coherent MIMO processing with the proximity gains of distributed antenna setups. In this paper, we analyze how transceiver hardware impairments affect the downlink with maximum ratio transmission. We derive closed-form spectral efficiencies expressions and study their asymptotic behavior as the number of the antennas increases. We prove a scaling law on the hardware quality, which reveals that massive MIMO is resilient to additive distortions, while multiplicative phase noise is a limiting factor. It is also better to have separate oscillators at each antenna than one per BS

  • 323.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten. KTH Royal Institute Technology, Sweden; Supelec, France.
    Sanguinetti, Luca
    University of Pisa, Italy; CentraleSupelec, France.
    Hoydis, Jakob
    Bell Labs, Germany.
    Debbah, Merouane
    CentraleSupelec, France.
    Optimal Design of Energy-Efficient Multi-User MIMO Systems: Is Massive MIMO the Answer?2015Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 14, nr 6, 3059-3075 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Assume that a multi-user multiple-input multiple-output (MIMO) system is designed from scratch to uniformly cover a given area with maximal energy efficiency (EE). What are the optimal number of antennas, active users, and transmit power? The aim of this paper is to answer this fundamental question. We consider jointly the uplink and downlink with different processing schemes at the base station and propose a new realistic power consumption model that reveals how the above parameters affect the EE. Closed-form expressions for the EE-optimal value of each parameter, when the other two are fixed, are provided for zero-forcing (ZF) processing in single-cell scenarios. These expressions prove how the parameters interact. For example, in sharp contrast to common belief, the transmit power is found to increase (not to decrease) with the number of antennas. This implies that energy-efficient systems can operate in high signal-to-noise ratio regimes in which interference-suppressing signal processing is mandatory. Numerical and analytical results show that the maximal EE is achieved by a massive MIMO setup wherein hundreds of antennas are deployed to serve a relatively large number of users using ZF processing. The numerical results show the same behavior under imperfect channel state information and in symmetric multi-cell scenarios.

  • 324.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Sanguinetti, Luca
    University of Pisa, Italy; University of Paris Saclay, France.
    Kountouris, Marios
    Huawei Technology Co Ltd, France.
    Deploying Dense Networks for Maximal Energy Efficiency: Small Cells Meet Massive MIMO2016Ingår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 34, nr 4, 832-847 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    What would a cellular network designed for maximal energy efficiency look like? To answer this fundamental question, tools from stochastic geometry are used in this paper to model future cellular networks and obtain a new lower bound on the average uplink spectral efficiency. This enables us to formulate a tractable uplink energy efficiency (EE) maximization problem and solve it analytically with respect to the density of base stations (BSs), the transmit power levels, the number of BS antennas and users per cell, and the pilot reuse factor. The closed-form expressions obtained from this general EE maximization framework provide valuable insights on the interplay between the optimization variables, hardware characteristics, and propagation environment. Small cells are proved to give high EE, but the EE improvement saturates quickly with the BS density. Interestingly, the maximal EE is achieved by also equipping the BSs with multiple antennas and operate in a "massive MIMO" fashion, where the array gain from coherent detection mitigates interference and the multiplexing of many users reduces the energy cost per user.

  • 325.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Sanguinetti, Luca
    University of Pisa, Italy; CentraleSupelec, France.
    Kountouris, Marios
    CentraleSupelec, France.
    Designing Wireless Broadband Access for Energy Efficiency: Are Small Cells the Only Answer?2015Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATION WORKSHOP, Institute of Electrical and Electronics Engineers (IEEE), 2015, 136-141 s.Konferensbidrag (Refereegranskat)
  • 326.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Sanguinetti, Luca
    University of Pisa, Italy; Central Supelec, France.
    Kountouris, Marios
    Huawei Technology Co Ltd, Peoples R China.
    Energy-Efficient Future Wireless Networks: A Marriage between Massive MIMO and Small Cells2015Ingår i: 2015 IEEE 16th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), IEEE , 2015, 211-215 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    How would a cellular network designed for high energy efficiency look like? To answer this fundamental question, we model cellular networks using stochastic geometry and optimize the energy efficiency with respect to the density of base stations, the number of antennas and users per cell, the transmit power levels, and the pilot reuse. The highest efficiency is neither achieved by a pure small-cell approach, nor by a pure massive MIMO solution. Interestingly, it is the combination of these approaches that provides the highest energy efficiency; small cells contributes by reducing the propagation losses while massive MIMO enables multiplexing of users with controlled interference.

  • 327.
    Blad, Anton
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Axell, Erik
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Spectrum Sensing of OFDM Signals in the Presence of CFO: New Algorithms and Empirical Evaluation Using USRP2012Ingår i: Proceedings of the 13th IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), IEEE , 2012, 159-163 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this work, we consider spectrum sensing of OFDM signals. We deal withthe inevitable problem of a carrier frequency offset, and propose modificationsto some state-of-the-art detectors to cope with that. Moreover, the (modified)detectors are implemented using GNU radio and USRP, and evaluated over aphysical radio channel. Measurements show that all of the evaluated detectorsperform quite well, and the preferred choice of detector depends on thedetection requirements and the radio environment.

  • 328.
    Blank, Bruno
    et al.
    KTH, Tidigare Institutioner, Teleinformatik.
    Häggström, Mattias
    KTH, Tidigare Institutioner, Teleinformatik.
    Mobile Communication In a Multiple Device Environment1998Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    It is nowadays common that users have more than one computer. At the office, a stationary computer or possibly a laptop is used. When travelling, a Personal Digital Assistant is better suited for e-mail, address book, and scheduling. Probably the user also has an advanced mobile phone. A problem for many users is it has traditionally been quite complex to handle having multiple computers, since the support for mobile use has been insufficient.

    We have looked into common scenarios for mobile users and given and overview of related products and technologies. Some of the traditional protocols for e-mail have been reviewed. We have listed problems with those and suggested improvements. Sendit has a proprietary protocol, which we have compared to traditional protocols.

    This report gives an overview from the user’s point of view. From what we have seen, there are lots of upcoming technologies and solutions to assist mobile users. However, many problems still remain and need to be solved to facilitate the mobile user’s situation.

  • 329.
    Blom, Rolf
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    An Upper Bound on the Key Equivocation for Pure Ciphers1979Rapport (Övrigt vetenskapligt)
    Abstract [en]

    An upper bound on key equivocation for a pure cipher applied on a memoryless message source is derived.

  • 330.
    Blom, Rolf
    et al.
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Fåk, Viiveke
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Ingemarsson, Ingemar
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Data Network Security: Part I Problem Survey and Model1977Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Data encryption and related methods may be used to preserve information security i n a data network. Here information security is defined as the degree to which the destruction, change or loss of information is presented. Information is defined as the content of the message represented by the data. The information in a block of data is unchanged if the intended result of the transmission of the block is obtained. This means for example that the original message reaches the correct destination where it is interpreted as intended. Undisturbed information does not, in general, require un disturbed data.

    The network is supposed to be a public network, accessed by many different users. We are interested in a well defined group of users who are communicating mainly among themselves. Different groups, however, are also allowed to communicate in a well defined manner. The logical structure of the communication within a group is star-shaped. The information communicated within the groups hall be protected against threats from other users of the network, from illegitimate users (wiretappers etc) and from members in the group. The structure of the threats is described in section 3 of this paper.

    The network itself and the requirement it imposes are supposed to be unchanged. Encryption and decryption are taking place outside the network. The encrypted data shall comply with the requirements of the network. The communication process in the group consists of time-limited messages which are essentially transmitted from one point to another in the network. This is the basis for the model of the communication which is described in section 4. The model, although simple, enables us to structure the problems in connection with encryption/decryption. This is done in section 5 and 6. The purpose of the paper is to form a basis for synthesis of security measures by means on cryptological methods. The analysis is general enough to be applied to any data network and any type of user group.

  • 331.
    Blomberg, Patrik
    KTH, Tidigare Institutioner, Teleinformatik.
    Construction and Implementation of a Walkstation Mobile-distributed File System Testbed1995Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this Master's Thesis an investigation, design and implementation of an object-oriented prototype of a new kind of client-agent-server based distributed file system, suited for wireless mobile computing, are presented. An overview is given of the characteristics and the inherent problems of mobile-wireless computing. Some solutions and techniques to reduce the effects of these problems are described. A presentation of a project (the Walkstation project) that tries to solve these problems is also given. Software to support a mobile-distributed file system is designed and implemented. Various software development techniques and mobile file system design solutions are proposed, and used in the implementation. An integrated caching and prefetching scheme with dynamically loadable cache and prefetch manager objects is designed and implemented. It is proposed that different cache and prefetch algorithms should be used for different kinds of network links. A cache/prefetch-manager object architecture with automatically location-dependant dynamical swapping of network specific manager objects at run-time is therefore proposed and implemented. A mechanism is designed with which an application optionally can be mobility-aware by subscribing for network-change events. Finally, an expedient example of a methodology to achieve easy-understandable and well-designed code, and good extensibility possibilities is explained and used in the development. This is done by utilizing an object-oriented software development methodology in the entire software development cycle.

  • 332. Boano, Carlo Alberto
    et al.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Noda, Claro
    Römer, Kay
    Zuniga, Marco
    JamLab: Augmenting sensornet testbeds with realistic and controlled interference generation2011Ingår i: IPSN, 2011, 175-186 s.Konferensbidrag (Refereegranskat)
  • 333.
    Boano, Carlo Alberto
    et al.
    University of Lübeck.
    Wennerström, Hjalmar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Zúñiga, Marco Antonio
    TU Delft.
    Brown, James
    Lancaster University.
    Keppitiyagama, Chamath
    Swedish Institute of Computer Science.
    Oppermann, Felix Jonathan
    University of Lübeck.
    Roedig, Utz
    Lancaster University.
    Nordén, Lars-Åke
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Römer, Kay
    University of Lübeck.
    Hot Packets: A systematic evaluation of the effect of temperature on low power wireless transceivers2013Ingår i: Proc. 5th Extreme Conference on Communication, New York: ACM Press, 2013, 7-12 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Temperature is known to have a significant effect on the performance of radio transceivers: the higher the temperature, the lower the quality of links. Analysing this effect is particularly important in sensor networks because several applications are exposed to harsh environmental conditions. Daily or hourly changes in temperature can dramatically reduce the throughput, increase the delay, or even lead to network partitions. A few studies have quantified the impact of temperature on low-power wireless links, but only for a limited temperature range and on a single radio transceiver. Building on top of these preliminary observations, we design a low-cost experimental infrastructure to vary the onboard temperature of sensor nodes in a repeatable fashion, and we study systematically the impact of temperature on various sensornet platforms. We show that temperature affects transmitting and receiving nodes differently, and that all platforms follow a similar trend that can be captured in a simple first-order model. This work represents an initial stepping stone aimed at predicting the performance of a network considering the particular temperature profile of a given environment.

  • 334. Boccardi, Federico
    et al.
    Andrews, Jeffrey
    Elshaer, Hisham
    Dohler, Mischa
    Parkvall, Stefan
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. Univ Calif San Diego, San Diego.
    Popovski, Petar
    Singh, Sarabjot
    Why to Decouple the Uplink and Downlink in Cellular Networks and How To Do It2016Ingår i: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 54, nr 3, 110-117 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ever since the inception of mobile telephony, the downlink and uplink of cellular networks have been coupled, that is, mobile terminals have been constrained to associate with the same base station in both the downlink and uplink directions. New trends in network densification and mobile data usage increase the drawbacks of this constraint, and suggest that it should be revisited. In this article we identify and explain five key arguments in favor of downlink/uplink decoupling based on a blend of theoretical, experimental, and architectural insights. We then overview the changes needed in current LTE-A mobile systems to enable this decoupling, and then look ahead to fifth generation cellular standards. We demonstrate that decoupling can lead to significant gains in network throughput, outage, and power consumption at a much lower cost compared to other solutions that provide comparable or lower gains.

  • 335.
    Bodinger, Ronnie
    KTH, Tidigare Institutioner, Teleinformatik.
    An MPLS Connection Manager for an Edge Router1998Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The Internet has been growing rapidly over the last couple of years. The increasing demand for network bandwidth is becoming a huge problem. To solve this problem, new methods must be developed. Ericsson’s solution is the use of MultiProtocol Label Switching (MPLS). MPLS has the potential to have a major impact on IP networking. It has the simplicity and dynamic nature of an IP network, but retains the performance of an ATM network. Furthermore, from an administrator’s point of view, MPLS will drastically simplify network management.

    The key principle behind MPLS is to be able to forward by switching packets through a network instead of routing packets. In order to do this, paths are established at the data link layer throughout the MPLS network. A fixed length identifier known as “label” identifies each path. Then the packets are simply forwarded on the path using layer two switching, instead of performing layer three routing.

    By using MPLS, performance is increased and it provides a good basis for traffic engineering, Quality of Service (QoS) guarantees, and Virtual Private Networks (VPN).

    I have implemented an MPLS ATM driver for an Ericsson AXI 510 Edge Router. The driver is responsible for converting generic MPLS labels into standard ATM labels (VPI/VCI). The driver also modifies the forwarding process in the router so that ATM paths are used to forward the packets, instead of the conventional forwarding methods. This implementation has been partly tested and it complies with MPLS current Internet drafts so far.

  • 336. Boeira, Felipe
    et al.
    Barcellos, Marinho
    Pignaton, Edison
    Vinel, Alexey
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Asplund, Mikael
    Effects of Colluding Sybil Nodes in Message Falsification Attacks for Vehicular Platooning2017Konferensbidrag (Refereegranskat)
  • 337.
    Bogdanov, Kirill
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Latency Dataset for the paper "The Nearest Replica Can Be Farther Than You Think"2015Dataset
  • 338.
    Bogdanov, Kirill
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Reducing Long Tail Latencies in Geo-Distributed Systems2016Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [sv]

    Databehandlingstjänster är en välintegrerad del av det moderna samhället. Miljontals människor förlitar sig dagligen på dessa tjänster för kommunikation, samordning, handel, och åtkomst till information. För att möta höga krav implementeras och placeras många populära tjänster som geo-fördelning applikationer ovanpå tredje parters virtuella molntjänster. Det ligger emellertid i sakens natur att sådana utplaceringar resulterar i varierande prestanda. För att leverera höga servicekvalitetskrav behöver sådana system sträva efter att ständigt anpassa sig efter ändrade förutsättningar genom att övervaka tillståndsändringar och ta realtidsbeslut, som till exempel val av server peering, replika placering, och val av kvorum.

    Den här avhandlingen avser att förbättra kvaliteten på realtidsbeslut tagna av geo-fördelning system. Detta kan uppnås genom: (1) en bättre förståelse av underliggande utplaceringsvillkor, (2) systematisk och noggrann testning av beslutslogik redan implementerad i dessa system, och (3) en tydlig inblick i nätverket och systemtillstånd som tillåter dessa tjänster att utföra mer informerade beslut.

    Vi utförde en långsiktig korsa datacenter latensmätning av Amazons EC2 molntjänst. Mätdata användes sedan till att kvantifiera variationen av nätverkstillstånd och demonstrera dess inverkan på prestanda för system placerade ovanpå denna molntjänst.

    Därnäst validerades en applikations beslutslogik vanlig i populära lagringssystem genom att undersöka replika valalgoritmen. GeoPerf, ett verktyg som tillämpar symbolisk exekvering och lättviktsmodellering för systematisk testning av replika valalgoritmen, användes för att testa två populära lagringssystem och vi hittade en bugg i båda.

    Genom traceroute och envägslatensmätningar över EC2 demonstrerar vi ihängande korrelation mellan nätverksvägar och nätverkslatens. Vi introducerar också EdgeVar, ett verktyg som frikopplar dirigering och trängsel baserat på förändringar i nätverkslatens. Genom att tillhandahålla denna ytterligare information förbättrade vi kvaliteten på latensuppskattningen och stabiliteten på nätverkets val av väg.

    Slutligen introducerade vi Tectonic, ett verktyg som följer en applikations begäran och gensvar på både användare-läge och kernel-läge. Tillsammans med EdgeVar förses en komplett bild av fördröjningar associerade med varje beräkningssteg av begäran och gensvar. Med Tectonic kunde vi analysera inverkan av att dela CPUer i en virtuell miljö och kan avslöja hypervisor schemaläggningsprinciper. Vi argumenterar för betydelsen av att känna till dessa principer och föreslå användningen av de i beslutsprocessen.

  • 339.
    Bogdanov, Kirill
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Peón-Quirós, Miguel
    Complutense University of Madrid.
    Maguire Jr., Gerald Q.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Kostic, Dejan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    The Nearest Replica Can Be Farther Than You Think2015Ingår i: Proceedings of the ACM Symposium on Cloud Computing 2015, Association for Computing Machinery (ACM), 2015, 16-29 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Modern distributed systems are geo-distributed for reasons of increased performance, reliability, and survivability. At the heart of many such systems, e.g., the widely used Cassandra and MongoDB data stores, is an algorithm for choosing a closest set of replicas to service a client request. Suboptimal replica choices due to dynamically changing network conditions result in reduced performance as a result of increased response latency. We present GeoPerf, a tool that tries to automate the process of systematically testing the performance of replica selection algorithms for geodistributed storage systems. Our key idea is to combine symbolic execution and lightweight modeling to generate a set of inputs that can expose weaknesses in replica selection. As part of our evaluation, we analyzed network round trip times between geographically distributed Amazon EC2 regions, and showed a significant number of daily changes in nearestK replica orders. We tested Cassandra and MongoDB using our tool, and found bugs in each of these systems. Finally, we use our collected Amazon EC2 latency traces to quantify the time lost due to these bugs. For example due to the bug in Cassandra, the median wasted time for 10% of all requests is above 50 ms.

  • 340.
    Bogdanov, Kirill
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Peón-Quirós, Miguel
    Complutense University of Madrid.
    Maguire Jr., Gerald Q.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Kostić, Dejan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Network Systems Laboratory (NS Lab).
    Toward Automated Testing of Geo-Distributed Replica Selection Algorithms2015Ingår i: Proceedings of the 2015 ACM Conference on Special Interest Group on Data Communication, Association for Computing Machinery (ACM), 2015, 89-90 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Many geo-distributed systems rely on a replica selection algorithms to communicate with the closest set of replicas.  Unfortunately, the bursty nature of the Internet traffic and ever changing network conditions present a problem in identifying the best choices of replicas. Suboptimal replica choices result in increased response latency and reduced system performance. In this work we present GeoPerf, a tool that tries to automate testing of geo-distributed replica selection algorithms. We used GeoPerf to test Cassandra and MongoDB, two popular data stores, and found bugs in each of these systems.

  • 341. Bohge, Mathias
    et al.
    Gross, James
    Wolisz, Mathias
    Optimal Power Masking in Soft Frequency Reuse based OFDMA Networks2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    Soft frequency reuse is a strong tool for co-channel interference mitigation in cellular OFDMAILTE networks. The performance of such networks significantly depends on the configuration of the power masks that implement the soft frequency reuse patterns. In this paper, we investigate the performance of different power mask configurations against the optimal case, in which a central entity optimally distributes power and resource blocks among the users of the network. It is shown that large differences exist between the performance of different mask types and the optimal case in both, the overall cell throughput, as well as the cell-edge user performance.

  • 342.
    Bohge, Mathias
    et al.
    TU Berlin.
    Naghibi, Farshad
    TU Berlin.
    Wolisz, Adam
    TU Berlin.
    The use of guard bands to mitigate multiple access interference in the OFDMA uplink2008Ingår i: Proceedings of the 13th International OFDM-Workshop (InOWo),, 2008, 75-79 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    The usual approach to mitigate multiple access interference (MAI) in the uplink of cellular OFDMA based systems is to use relatively large cyclic prefixes as time domain guard periods. In this paper, we suggest to use a combination of short time domain guard periods and frequency domain guard bands to protect against MAI instead. Guard bands can be added and removed as necessary and, thus, increase the MAI protection flexibility. We show that, if optimally applied, the use of guard bands can significantly increase the system’s uplink capacity or minimum capacity per user.

  • 343.
    Boin, Arjen
    et al.
    Crisisplan & Leiden University.
    Bynander, Fredrik
    Försvarshögskolan, Institutionen för säkerhet, strategi och ledarskap (ISSL), CRISMART (Nationellt Centrum för Krishanteringsstudier).
    Pintore, Giovanni
    CRS4 Visual Computing Group Pula(CA), Italy.
    Ganovelli, Fabio
    ISTI-CNR Pisa, Italy.
    Leventakis, George
    Center for Security Studies - KEMEA Athens, Greece.
    Ahmad, Alexandre
    DIGINEXT Toulouse, France.
    Balet, Olivier
    DIGINEXT Toulouse, France.
    Building an IT Platform for Strategic Crisis Management Preparation2014Ingår i: 10th International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob), IEEE conference proceedings, 2014, 20-27 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents the result of the work achieved in the frame of three successive European Projects, which aimed to build an innovative system to assist security managers in the crisis preparation, training and management phases. The iterative approach of the consortium is presented, as well as the results. A novel interactive and shared Common Operational Picture is proposed which has been validated by three large scale demonstrations. On-going and future work focusing on the security concepts and measures of building interiors is moreover presented.

  • 344. Bonanni, L
    et al.
    Ebner, Hannes
    Hockenberry, M
    Sayan, B
    Brandt, Nils
    Csikszentmihàlyi, N
    Ishii, H
    Turpeinen, Marko
    Young, S
    Zapico, Jorge Luis
    KTH Royal Institute of Technology.
    Sourcemap. org: First Application of Linked and Open LCA Data to Support Sustainability2011Konferensbidrag (Refereegranskat)
  • 345.
    Bonanni, Leonardo
    et al.
    MIT Media Lab, USA.
    Ebner, Hannes
    KTH Royal Institute of Technology.
    Hockenberry, Matthew
    MIT Media Lab , USA.
    Sayan, Bianca
    University of Waterloo , Canada.
    Zapico Lamela, Jorge Luis
    KTH Royal Institute of Technology.
    Brandt, Nils
    MIT Media Lab, USA.
    Csikszentmihàlyi, Chris
    MIT Media Lab , USA.
    Ishii, Hiroshi
    MIT Media Lab, USA.
    Turpeinen, Marko
    MIT Media Lab, USA.
    Young, Steven
    University of Waterloo, Canada.
    The Open Sustainability Project: A Linked Data Approach to LCA2010Ingår i: LCA X, Bridging Science, Policy, and the Public 2-4 November 2010, Portland, Oregon, 2010Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The proprietary nature of LCA tools and information limits widespread adoption of sustainability measures. We introduce the Open Sustainability Project(OSP), a Linked Data resource for broadening access to LCA in an effort to increase the transparency and accuracy of environmental impact assessments(2, 9).The OSP applies Free and Open Source Software(FOSS) principles and Linked Data structures to LCA standards and reporting so that communities including students, SME’s and the general public can participate in the assessment and verification of sustainability practices(1,6). The highly flexible data format allows disparate data sources and assessments to be compared along an open standard compliant with ISO 14048 reporting(5, 8, 12).In addition, the OSP makes available a free database of Life Cycle Assessment data using an approach based on Linked Data and RESTful interfaces which supports the development of rich third-party applications for specific user groups and industries(7). This novel combination of linked data and web-based tools is inherently transparent so that LCA practices can be standardized, compared and verified by a broad community.The OSP is an international collaboration between academics, government and industry groups leveraging expertise in LCA, Open Data and web-based tools for sustainability(10). Our first Open Source and Open Data web sustainability tools have confirmed the potential to engage a wider audience, with over two thousand registered users, three thousand environmental assessments performed and over 330,000 page views from more than 75 countries since September 2009(3, 4, 11). The OSP aims to expand reach of LCA through a free and open Application Programming Interface(API) to support distributed development of third-party applications for sustainability assessment through the emerging metrics for social and environmental sustainability(a free LCA "App Store"). These applications are intended to disseminate LCA standards, encourage transparency in environmental reporting and leverage Collective Intelligence in the collection, publication and verification of LCA.The OSP aims to transform LCA into a collaborative process where data collection, analysis, assessment and reporting benefit from the feedback and ideas of a growing worldwide LCA community.

  • 346.
    Bondarevs, Andrejs
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Huss, Patrik
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Ye, Qin-Zhong
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Gong, Shaofang
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Universal Internet of Things Solution: Protocol Independent2017Ingår i: 2017 IEEE INTERNATIONAL CONFERENCE ON INDUSTRIAL TECHNOLOGY (ICIT), IEEE , 2017, 1313-1318 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    The diversity of wireless networks and protocols used by Internet of Things makes solutions non-interoperable. Moreover, some Things are not always able to communicate due to resource constrains or environmental factors. In this paper, those issues are addressed by introducing the concept of virtual Things. It means that each real Thing is virtualized in a local server or in the cloud, enabling communication with the user through a common protocol, i.e., the Internet Protocol. The virtual Thing has its own Internet Protocol address and authentication measure to control the access.

  • 347.
    Boonphoka, Terut
    et al.
    School of Electron. Inf. & Commun., Huazhong Univ. of Sci. & Technol., Wuhan, China.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Zhong, Yi
    School of Electron. Inf. & Commun., Huazhong Univ. of Sci. & Technol., Wuhan, China.
    Ge, Xiaohu
    School of Electron. Inf. & Commun., Huazhong Univ. of Sci. & Technol., Wuhan, China.
    Uthansakul, Peerapong
    Dept. of Telecommunication Engineering, Suranaree Univ. of Technol., Thailand.
    Quek, Tony
    Dept. of Inf. Systems Technol. & Design, Singapore Univ. of Technol. & Design, Singapore.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Performance Analysis of Full-Duplex Relay Channel with Random Access2017Ingår i: IEEE Global Communications Conference: Workshops: Workshop on Full-­Duplex Communications for Future Wireless Networks, 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Relay is useful in wireless networks to assist the sources to deliver packets to the destinations. In this paper, the effect of full-duplex relay with random access is evaluated. Based on the model of two sources, two destinations, and one full-duplex relay with two queues, we obtain the analytical expressions for significant parameters, such as the arrival rate and the service rate for queues at the relay. Then, we evaluate the per-user throughput and the per-user average delay as functions of the signal-to-interference-plus-noise ratio (SINR) threshold and the self-interference cancelation coefficient through both analysis and simulation. We also consider the case where the two queues at the relay have different priorities and evaluate the effect of different transmit probabilities on the system performance. Our results reveal that the transmit probabilities and the transmit powers have an enormous impact on the self-interference, the average size and the empty probability of the queues. Specially, the queues tend to be stable when increasing the transmit probabilities and the transmit powers.

  • 348.
    Booth, Todd
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Andersson, Karl
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Critical Infrastructure Network DDoS Defense, via Cognitive Learning2017Ingår i: / [ed] Pietro Manzoni, Universitat Politècnica de València, Spain, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Some public and private services are called part of the Critical Infrastructure (CI), which are considered as the most important services to protect the functioning of a society and the economy.  Many CIs provide services via the Internet and thus cyber-attacks can be performed remotely.  It is now very simple and free to find and download software, which automates performing cyber-attacks.  A recent example is that two teenagers, with close to no security knowledge, created an on-line business. They would run cyber-attacks (online booter service called vDOS, as reported by Brian Krebs) for a small fee. They reportedly earned over 600,000 USD in a short period of time by conducting a large number of automated DDoS cyber-attacks. Then Krebs was retaliated against, and the highest DDoS attack bandwidth ever recorded, 620 Gbps, was launched against Krebs. In this paper we show how cognitive learning can be used to significantly mitigate any effects of DDoS network attacks, against the critical infrastructure.

  • 349.
    Borges Vieira, Alex
    et al.
    Universidade Federal de Juiz de Fora, DCC-UFJF.
    Couto da Silva, Ana Paula
    Universidade Federal de Juiz de Fora, DCC-UFJF.
    Henrique, Francisco
    Universidade Federal de Juiz de Fora, DCC-UFJF.
    Goncalves, Glauber
    Universidade Federal de Minas Gerais, DCC-UFMG.
    de Carvalho Gomes, Pedro
    KTH, Skolan för datavetenskap och kommunikation (CSC), Teoretisk datalogi, TCS.
    SopCast P2P live streaming: live session traces and analysis2013Ingår i: Proceedings of the 4th ACM Multimedia Systems Conference: MMSys 2013, Association for Computing Machinery (ACM), 2013, 125-130 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    P2P-TV applications have attracted a lot of attention fromthe research community in the last years. Such systemsgenerate a large amount of data which impacts the networkperformance. As a natural consequence, characterizingthese systems has become a very important task to developbetter multimedia systems. However, crawling data fromP2P live streaming systems is particularly challenging bythe fact that most of these applications have privateprotocols. In this work, we present a set of logs from a verypopular P2P live streaming application, the SopCast. Wedescribe our crawling methodology, and present a briefSopCast characterization. We believe that our logs and thecharacterization can be used as a starting point to thedevelopment of new live streaming systems.

  • 350. Borgh, Joakim
    et al.
    Ngai, Edith
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Ohlman, Börje
    Malik, Adeel Mohammad
    Employing attribute-based encryption in systems with resource constrained devices in an information-centric networking context2017Ingår i: Proc. 1st Global Internet of Things Summit, Piscataway, NJ: IEEE, 2017, 397-402 s.Konferensbidrag (Refereegranskat)
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