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  • 1.
    Dadhich, Siddharth
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Sandin, Fredrik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Andersson, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Martinsson, Torbjörn
    Volvo CE, Bolindervägen 5, 63185 Eskilstuna, Sweden.
    Field test of neural-network based automatic bucket-filling algorithm for wheel-loaders2019Ingår i: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 97, s. 1-12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Automation of earth-moving industries (construction, mining and quarry) require automatic bucket-filling algorithms for efficient operation of front-end loaders. Autonomous bucket-filling is an open problem since three decades due to difficulties in developing useful earth models (soil, gravel and rock) for automatic control. Operators make use of vision, sound and vestibular feedback to perform the bucket-filling operation with high productivity and fuel efficiency. In this paper, field experiments with a small time-delayed neural network (TDNN) implemented in the bucket control-loop of a Volvo L180H front-end loader filling medium coarse gravel are presented. The total delay time parameter of the TDNN is found to be an important hyperparameter due to the variable delay present in the hydraulics of the wheel-loader. The TDNN network successfully performs the bucket-filling operation after an initial period (100 examples) of imitation learning from an expert operator. The demonstrated solution show only 26% longer bucket-filling time, an improvement over manual tele-operation performance.

  • 2.
    Palm, Emanuel
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Paniagua, Cristina
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Schelén, Olov
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Syntactic Translation of Message Payloads Between At Least Partially Equivalent Encodings2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Recent years have seen a surge of interest in using IoT systems for an increasingly diverse set of applications, with use cases ranging from medicine to mining. Due to the disparate needs of these applications, vendors are adopting a growing number of messaging protocols, encodings and semantics, which result in poor interoperability unless systems are explicitly designed to work together. Key efforts, such as Industry 4.0, put heavy emphasis on being able to compose arbitrary IoT systems to create emergent applications, which makes mitigating this barrier to interoperability a significant objective. In this paper, we present a theoretical method for translating message payloads in transit between endpoints, complementing previous work on protocol translation. The method involves representing and analyzing encoding syntaxes with the aim of identifying the concrete translations that can be performed without risk of syntactic data loss. While the method does not facilitate translation between all possible encodings or semantics, we believe that it could be extended to enable such translation.

  • 3.
    Palm, Emanuel
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Schelén, Olov
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Hedman, Richard
    Volvo Group Trucks Operations, Göteborg, Sweden.
    The Exchange Network: An Architecture for the Negotiation of Non-Repudiable Token Exchanges2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Many use cases coming out of initiatives such as Industry 4.0 and Ubiquitous Computing require that systems be able to cooperate by negotiating about and agreeing on the exchange of arbitrary values. While solutions able to facilitate such negotiation exist, they tend to either be domain-specific or lack mechanisms for non-repudiation, which make them unfit for the heterogeneity and scale of many compelling applications. In this paper, we present the Exchange Network, a general-purpose and implementation-independent architecture for digital negotiation and non-repudiable exchanges of tokens, which are symbolic representations of arbitrary values. We consider the implications of implementing the architecture in three different ways, using a common database, a blockchain, and our own Signature Chain data structure, which we also describe. We demonstrate the feasibility of the architecture by outlining our own implementation of it and also describe a supply-chain scenario inspired by one transportation process at Volvo Trucks.

  • 4.
    Johansson, Ingemar
    et al.
    Ericsson AB, Luleå.
    Dadhich, Siddharth
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Jönsson, Tomas
    Ericsson AB, Luleå.
    Adaptive Video with SCReAM over LTE for Remote-Operated Working Machines2018Ingår i: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 2018, artikel-id 3142496Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Remote operation is a step toward the automation of mobile working machines. Safe and efficient teleremote operation requires good-quality video feedback. Varying radio conditions make it desirable to adapt the video sending rate of cameras to make the best use of the wireless capacity. The adaptation should be able to prioritize camera feeds in different directions depending on motion, ongoing tasks, and safety concerns. Self-Clocked Rate Adaptation for Multimedia (SCReAM) provides a rate adaptation algorithm for these needs. SCReAM can control the compression used for multiple video streams using differentiating priorities and thereby provide sufficient congestion control to achieve both low latency and high video throughput. We present results from the testing of prioritized adaptation of four video streams with SCReAM over LTE and discuss how such adaptation can be useful for the teleremote operation of working machines.

  • 5.
    Dadhich, Siddharth
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Sandin, Fredrik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Andersson, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    From Tele-remote Operation to Semi-automated Wheel-loader2018Ingår i: International Journal of Electrical and Electronic Engineering and Telecommunications, ISSN 2319-2518, Vol. 7, nr 4, s. 178-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents experimental results with tele-remote operation of a wheel-loader and proposes a method to semi-automate the process. The different components of the tele-remote setup are described in the paper. We focus on the short loading cycle, which is commonly used at quarry and construction sites for moving gravel from piles onto trucks. We present results from short-loading-cycle experiments with three operators, comparing productivity between tele-remote operation and manual operation. A productivity loss of 42% with tele-remote operation motivates the case for more automation. We propose a method to automate the bucket-filling process, which is one of the key operations performed by a wheel-loader.

  • 6.
    Dadhich, Siddharth
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Sandin, Fredrik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Predicting bucket-filling control actions of a wheel-loader operator using aneural network ensemble2018Ingår i: 2018 International Joint Conference on Neural Networks (IJCNN), Piscataway, NJ: IEEE, 2018, artikel-id 8489388Konferensbidrag (Refereegranskat)
    Abstract [en]

    Automatic bucket filling is an open problem since three decades. In this paper, we address this problem with supervised machine learning using data collected from manual operation. The range-normalized actuations of lift joystick, tilt joystick and throttle pedal are predicted using information from sensors on the machine and the prediction errors are quantified. We apply linear regression, k-nearest neighbors, neural networks, regression trees and ensemble methods and find that an ensemble of neural networks results in the most accurate predictions. The prediction root-mean-square-error (RMSE) of the lift action exceeds that of the tilt and throttle actions, and we obtain an RMSE below 0.2 for complete bucket fillings after training with as little as 135 bucket filling examples

  • 7.
    Palm, Emanuel
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Schelén, Olov
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Selective Blockchain Transaction Pruning and State Derivability2018Ingår i: 2018 Crypto Valley Conference on Blockchain Technology: CVCBT 2018, 2018, s. 31-40Konferensbidrag (Refereegranskat)
    Abstract [en]

    Distributed ledger technologies, such as blockchain systems, have in recent years emerged as promising platforms for machine-to-machine commerce and other forms of multi-stakeholder applications. However, despite the potential demonstrated by projects such as Bitcoin, Ethereum, and Hyperledger Fabric, the disk space typically required to host a copy of a ledger may be prohibitively large for many categories of devices. In this paper, we introduce an approach for reducing ledger size in blockchain systems, based on arbitrary pruning predicate functions, allowing each network participant to independently select and remove any already applied transactions. We also show that if only pruning certain ledger transactions, the ability to derive an unmodified state data structure from the remaining transactions is maintained. The approach is validated through a supply chain use case utilizing a modified version of Hyperledger Fabric, in which ledger size is reduced by about 84.49% via selective transaction pruning.

  • 8.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Reusable road condition information system for traffic safety and targeted maintenance2017Ingår i: IET Intelligent Transport Systems, ISSN 1751-956X, E-ISSN 1751-9578, Vol. 11, nr 4, s. 230-238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Driver awareness of current winter road conditions (RCs) is known to affect the frequency of accidents due to sudden changes in these conditions. For example, partially icy roads that appear during autumn in northern areas typically result in collisions and ditch runs unless the drivers are generally aware of the situation. Availing motorists who drive under winter RCs of enhanced information is therefore highly desirable to increase their awareness of hazardous driving conditions. Such conditions need to be predicted ahead of time and presented to drivers before they attempt slippery road sections. Moreover, the identification of slippery RCs should quickly trigger targeted road maintenance to reduce the risk of accidents. This study presents a scalable and reusable collaborative intelligent transport system, herein referred to as an RC information system (RCIS). RCIS provides accurate RC predictions and forecasts based on RC measurements, road weather observations, and short-term weather forecasts. The prediction methods in the context of the distributed RCIS have been tested using a prototype implementation. These tests confirmed that these inputs could be combined into useful and accurate information about winter RCs that can be adapted for different types of users.

  • 9.
    Dadhich, Siddharth
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Andersson, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Key challenges in automation of earth-moving machines2016Ingår i: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 68, s. 212-222Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A wheel loader is an earth-moving machine used in construction sites, gravel pits and mining to move blasted rock, soil and gravel. In the presence of a nearby dump truck, the wheel loader is said to be operating in a short loading cycle. This paper concerns the moving of material (soil, gravel and fragmented rock) by a wheel loader in a short loading cycle with more emphasis on the loading step. Due to the complexity of bucket-environment interactions, even three decades of research efforts towards automation of the bucket loading operation have not yet resulted in any fully autonomous system. This paper highlights the key challenges in automation and tele-remote operation of earth-moving machines and provides a survey of different areas of research within the scope of the earth-moving operation. The survey of publications presented in this paper is conducted with an aim to highlight the previous and ongoing research work in this field with an effort to strike a balance between recent and older publications. Another goal of the survey is to identify the research areas in which knowledge essential to automate the earth moving process is lagging behind. The paper concludes by identifying the knowledge gaps to give direction to future research in this field.

  • 10.
    Dadhich, Siddharth
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Sandin, Fredrik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Andersson, Ulf
    Machine Learning approach to Automatic Bucket Loading2016Ingår i: 24th Mediterranean Conference on Control and Automation (MED): June 21-24, Athens, Greece, 2016, Piscataway, NJ: IEEE Communications Society, 2016, s. 1260-1265, artikel-id 7535925Konferensbidrag (Refereegranskat)
    Abstract [en]

    The automation of bucket loading for repetitive tasks of earth-moving operations is desired in several applications at mining sites, quarries and construction sites where larger amounts of gravel and fragmented rock are to be moved. In load and carry cycles the average bucket weight is the dominating performance parameter, while fuel efficiency and loading time also come into play with short loading cycles. This paper presents the analysis of data recorded during loading of different types of gravel piles with a Volvo L110G wheel loader. Regression models of lift and tilt actions are fitted to the behavior of an expert driver for a gravel pile. We present linear regression models for lift and tilt action that explain most of the variance in the recorded data and outline a learning approach for solving the automatic bucket loading problem. A general solution should provide good performance in terms of average bucket weight, cycle time of loading and fuel efficiency for different types of material and pile geometries. We propose that a reinforcement learning approach can be used to further refine models fitted to the behavior of expert drivers, and we briefly discuss the scooping problem in terms of a Markov decision process and possible value functions and policy iteration schemes.

  • 11.
    Bodin, Ulf
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Grane, Camilla
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Lööw, Joel
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Teknisk rapport BASIE: Bärbara sensorer för ökad personsäkerhet2016Rapport (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

    Industriella arbetsmiljöer utgör trots omfattande säkerhetsarbete fortfarande en risk för hälsa och välbefinnande för arbetstagarna. Moderna sensorer och tekniker möjliggör att upptäcka risker och olyckor i tid och därmed öka säkerheten inom industrier. Industriella miljöer utrustas idag ofta med vältäckande trådlösa kommunikationsnät som möjliggör positionering och kommunikation med sensorer som bärs av personal. Den här rapporten beskriver aktuella tillämpningar och tekniklösningar. Förstudien har inte identifierat någon särskild tillämpning som kraftfullt driver utveckling av bärbara sensorer för industriella miljöer. Däremot har ett flertal lovande tillämpningar hittats som för närvarande provas av industrier eller finns kommersiellt tillgängliga som tidiga produkter. Några initiativ kan stödja flera tillämpningar och/eller funktioner med samma arkitektur och hårdvara. Flera lösningar bygger på positionering och i viss mån kontextanpassning.

     

    För fortsatt arbete föreslås utvärdera tillämpningar såsom (1) insamling av information för bättre uppföljning och analys av tillbud och olyckor, (2) stöd för genomförande av säkerhetsförbättrande åtgärder, baserat på analys av tillbud/olycka eller av annan anledning, samt (3) automatisk larmning vid ensamarbete och/eller särskilt riskfyllt arbete. Som ansats för fortsatt arbete föreslås att (A) definiera en flexibel arkitektur som möjliggör tester med olika typer av sensorer för olika tillämpningar, och etablera ett sådant testsystem, (B) identifiera existerande system till vilka integration behövs, samt (C) definiera återanvändbara funktioner för att säkert skydda den personliga integriteten efter behov som styrs av aktuell tillämpning och överenskommelse med företrädare för personal (dvs. fackföreningar), samt (D) hitta tydliga och väl avgränsade tillämpningar som kan provas praktiskt i målmiljöer.

  • 12.
    Bodin, Ulf
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Wolosz, Krzysztof
    Proportional throughput differentiationwith cognitive load-control on WSN channels2015Ingår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, nr 1, artikel-id 186Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wireless sensor networks are nowadays used in various applications to facilitate monitoring and actuation tasks, e.g., for smart grids and industrial automation. Some of these applications require guarantees or at least assurances on reliability. Such applications expect predictable throughput and delay, which are hard to maintain in environments with changing radio conditions. QoS-aware MAC protocols capable of handling such environments are well explored. They require however protocol changes and are therefore difficult to deploy. This paper presents an application layer forwarding service that offers proportional differentiation while limiting network load to preserve high utilization and predictability. Demands for capacity are expressed as fractions of the overall channel throughput. We show that this service can be implemented with a cognitive load controller (CLC) based on fuzzy logic and quality assessed with utility functions for application layer packet loss and throughput. We evaluate the CLC for 802.15.4 with CSMA/CA through NS-3 simulations showing that it offers the intended service while adjusting load for high overall throughput and low delay

  • 13.
    Bodin, Ulf
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Andersson, Ulf
    Dadhich, Siddharth
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Uhlin, Erik
    Volvo Construction Equipment.
    Marklund, Ulf
    Boliden AB.
    Häggström, Derny
    Oryx Simulations AB.
    Remote Controlled Short-Cycle Loading of Bulk Material in Mining Applications2015Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-capacity wireless IP networks with limited delays are nowadays being deployed in both underground and open-pit mines. This allows for advanced remote control of mining machinery with improved feedback to operators and extensive monitoring of machine status, wear and fatigue. Wireless connectivity varies however depending on channel impairments caused by obstacles, multi-path fading and other radio issues. Therefore remote control and monitoring should be capable of adapting their sending rates to handle variations in communications quality. This paper presents key challenges in advanced remote control and monitoring of working machines via high-capacity wireless IP networks in mining environments. We reason about these challenges in context of underground short-cycle load, haul and dump operation with large-volume built wheel-loaders and present a generic communication solution for an operator assistance concept capable of adapting to varying communication properties

  • 14.
    Wolosz, Krzysztof
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Osipov, Evgeny
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Eliasson, Jens
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Cognitive load-control for congested Wireless Sensor Network channels2013Ingår i: 2013 IFIP Wireless Days (WD 2013: Valencia, Spain, 13-15 Nov 2013, Piscataway, NJ: IEEE Communications Society, 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Modern wireless sensors transmit at high rates and changing transmission patterns. They may individually or collectively select how much data shall be sent depending on predefined rules tied to properties of measured data. Sending rates thereby change triggered by events appearing in the sensor environment. With wireless technologies such as 802.15.4 (ZigBee) having limited capacity high transmission needs can easily cause overload resulting in decreased throughput. This paper presents a load control mechanism that uses multiple inputs, demand for transmission capacity and perceived quality of each sensor node, to properly configure sending rates of these nodes. The mechanism is based on Fuzzy Logic and quality assessed with utility functions for packet loss and throughput. NS-3 simulation results show clear improvements in overall throughput at high loads with the mechanism compared to without.

  • 15.
    Wolosz, Krzysztof
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Riliskis, Laurynas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    A measurement study for predicting throughput from LQI and RSSI2012Ingår i: Multiple Access Communications: 5th International Workshop, MACOM 2012, Maynooth, Ireland, November 19-20, 2012. Proceedings / [ed] Boris Bellalta, Heidelberg: Encyclopedia of Global Archaeology/Springer Verlag, 2012, s. 89-92Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wireless sensor networks (WSN) commonly use ZigBee to communicate, especially when low power consumption is demanded. ZigBee may however provide unpredictable throughput although transmission distances are short. This is especially evident in difficult environments with complicated reflections and various materials through which radio signals need to pass through. Distributed scheduling based on cognitive networking principles may improve both network predictability and overall throughput. This paper presents measurements of key parameters for such cognitive scheduling, and discusses their potential for predicting suitable per-node transmission rates. Results include variability of throughput, RSSI and LQI observed for different transmission powers, transmission ranges, and number of transmitting nodes.

  • 16.
    Wolosz, Krzysztof
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Riliskis, Laurynas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    A measurement study of predicting throughput from LQI and RSSI2012Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Wireless sensor networks (WSN) commonly use ZigBee tocommunicate, especially when low power consumption is demanded. Zig-Bee may however provide unpredictable throughput although transmis-sion distances are short. This is especially evident in difficult environ-ments with complicated reflections and various materials through whichradio signals need to pass through. Distributed scheduling based on cog-nitive networking principles may improve both network predictabilityand overall throughput. This paper presents measurements of key pa-rameters for such cognitive scheduling, and discusses their potential forpredicting suitable per-node transmission rates. Results include variabil-ity of throughput, RSSI and LQI observed for different transmission pow-ers, transmission ranges, and number of transmitting nodes.

  • 17.
    Khattak, Rabiullah
    et al.
    Luleå tekniska universitet.
    Chaltseva, Anna
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Riliskis, Laurynas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Osipov, Evgeny
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Comparison of wireless network simulators with multihop wireless network testbed in corridor environment2011Ingår i: Wired/wireless internet communications: 9th IFIP TC 6 International Conference, WWIC 2011, Vilanova i la Geltrú, Spain, June 15-17, 2011 ; proceedings / [ed] Xavier Masip-Bruin, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2011, s. 80-91Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a comparative study between results of a single channel multihop wireless network testbed and the network simulators ns-2 and ns-3. We explore how well these simulators reflect reality with their standard empirical radio modeling capabilities. The environment studied is a corridor causing wave-guiding propagation phenomena of radio waves, which challenges the radio models used in the simulators. We find that simulations are roughly matching with testbed results for single flows, but clearly deviate from testbed results for concurrent flows. The mismatch between simulations and testbed results is due to imperfect wireless propagation channel modeling. This paper reveals the importance of validating simulation results when studying single channel multihop wireless network performance. It further emphasizes the need for validation when using empirical radio modeling for more complex environments such as corridors.

  • 18.
    Folke, Mats
    et al.
    Ericsson Research, Luleå.
    Landström, Sara
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Wänstedt, Stefan
    Ericsson Research, Luleå.
    Scheduling support for mixed VoIP and web traffic over HSDPA2007Ingår i: 2007 IEEE 65th Vehicular Technology Conference: 22 - 25 April 2007, Dublin, Ireland, Piscataway, NJ: IEEE Communications Society, 2007, s. 814-818Konferensbidrag (Refereegranskat)
    Abstract [en]

    HSDPA (high-speed downlink packet access), introduced in WCDMA release 5, provides a high-bandwidth shared channel with short transmission time interval (TTI). The short TTI together with appropriate scheduling enable HSDPA to support efficient multiplexing of traffic. We explain the performance of four scheduling algorithms when transmitting a traffic mix consisting of both conversational (VoIP) traffic and background (Web) traffic over the high-speed downlink shared channel (HS-DSCH) of HSDPA. We consider both cell throughput and user satisfaction. The proportional fair (PF), the maximum rate (MR) scheduler and two extended versions of MR, are tested for different VoIP scheduling delay budgets and varying load. To understand the behaviour of the schedulers, we use the ns-2 simulator extended with a model of HS-DSCH to simulate a mixed traffic scenario. Our results show that a scheduler that gradually increases the VoIP priority and considers the user's current possible rate, performs well. A more drastic increase in VoIP priority is however needed when the delay budget is short. Furthermore, attempting to uphold quality for both VoIP and Web traffic makes the system sensitive to overload situations.

  • 19.
    Bodin, Ulf
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Schelén, Olov
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Vemmervik, Claes
    Operax AB.
    End-to-End QoS control architectures from a wholesale and retail perspective: benefits and challenges2006Konferensbidrag (Refereegranskat)
  • 20. Folke, Mats
    et al.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    On the influence of user behaviour and admission control on system performance in HS-DSCH2006Ingår i: IEEE 63rd Vehicular Technology Conference: VTC 2006-Spring ; 7 - 10 May 2006, Melbourne, Australia ; proceedings, Piscataway, NJ: IEEE Communications Society, 2006, Vol. 1, s. 378-382Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we investigate the need for admission control for the high-speed downlink shared channel (HS-DSCH) through the evaluation of two admission control mechanisms. One mechanism uses the number of active users in a cell as a metric and the other one uses the mean downlink throughput of a user. We also introduce a model for user behaviour in which the goodput of a completed file download decides if further downloads are made. In order to measure user-experienced quality we use a utility function for transforming per-flow goodput into a user satisfaction index. System performance, measured by total user satisfaction and total goodput, is evaluated for a range of session arrival rates and admission control limits. This evaluation is done using the ns-2 simulator, together with extensions of our own. If the objective is to maximise goodput, our results show that no admission control is needed. Maximising user satisfaction benefits from an admission control. We also note that the impact of user behaviour is not insignificant.

  • 21.
    Sandström, Helena
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Schelén, Olov
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Adaptive threshold-based admission control2005Ingår i: ICC 2005: 2005 IEEE International Conference on Communications ; 16 - 20 May 2005, Seoul, Korea, Piscataway, NJ: IEEE Communications Society, 2005, s. 48-52Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present an algorithm for performing dynamic per-link admission control. It is designed to be suitable for deployment using existing quality of service and router techniques. The rationale for the algorithm is to find a bitrate limit for reserved capacity, which enables efficient capacity utilization and statistical multiplexing gain. By using simple traffic meters configured with respect to defined service levels, a network resource controller estimates an admission limit. The estimated limit reflects the ratio between reserved capacity and the aggregate behavior of current flows. Simulations indicate that reliable admission limits can be estimated already at low reservation levels.

  • 22. Landström, Sara
    et al.
    Larzon, Lars-Åke
    Uppsala University.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Buffer management for TCP over HS-DSCH2005Rapport (Övrigt vetenskapligt)
    Abstract [en]

    In this paper we investigate the influence of buffer management for TCP on performance of the High Speed Downlink Channel (HS-DSCH) introduced in WCDMA release 5. HS-DSCH is a shared channel, but user data is buffered individually prior to the wireless link. Three queue management principles, e.g., passive queuing, the Packet Discard Prevention Counter (PDPC) method and the Random Early Detection (RED) algorithm were evaluated for a number of buffer sizes and scenarios. Also, a buffer large enough to prevent packets from being lost was included for reference. For round robin (RR) scheduling of radio-blocks, PDPC and the passive approach, that both manage to keep the buffer short, gave the best system goodput as well as the shortest average transfer times together with the excessively large buffer. With signal-to-interference ratio (SIR) scheduling, the strategy to avoid all packet losses, resulted in a lower system goodput than for the short buffers. As illustrated in this article, peak transfer rates may not be achieved with very small buffers, but buffers of 10-15 IP packets seem to represent a good trade-off between transfer rates, delay and system goodput. We would like to investigate how to make use of system parameters such as the current amount of data offered for HS-DSCH in total to regulate individual buffer sizes.

  • 23. Folke, Mats
    et al.
    Landström, Sara
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    On the TCP minimum retransmission timeout in a high-speed cellular network2005Ingår i: Proceedings of the Eleventh European Wireless Conference, 2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    HS-DSCH is a high-speed shared radio channel extension for WCDMA which is used for cellular mobile telephony. The algorithm for distributing the channel resources together with the characteristics of the radio medium result in delay variations. The TCP minimum retransmission timeout interval has effectively alleviated delay variations in its range from deteriorating TCP performance. But recently, this bound has been shortened in modern widely spread TCP implementations. The aim of our study is to find out how a shorter minimum retransmission timeout affects TCP performance over HS-DSCH. We have implemented a model of HS-DSCH in the network simulator ns-2. Our simulations cover a wide range of different minimum retransmission timeout settings and loads, two types of schedulers (Round-Robin and Signalto-Interference-Ratio (SIR) scheduling) and two versions of TCP (SACK and NewReno). Our results show that the number of spurious timeouts increase with the load. The SIR scheduler causes fewer spurious timeouts than the RR scheduler for shorter minimum retransmission timeout settings, however, for longer settings the RR scheduler causes fewer spurious timeouts compared to the SIR scheduler. The minimum retransmission timeout has consequences for goodput fairness, but it does not affect the total system throughput. Both TCP versions produced similar results.

  • 24. Landström, Sara
    et al.
    Larzon, Lars-Åke
    Uppsala University.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Congestion control in a high-speed radio environment2004Ingår i: Proceedings of the International Conference on Wireless Networks, ICWN '04: Las Vegas, Nevada, USA, June 21 - 24, 2004 / [ed] Hamid R. Arabnia; Laurence Tianruo Yang; Chi-Hsiang Yeh, CSREA Press, 2004, s. 617-623Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper explores interactions between congestion control mechanisms at the transport layer and scheduling algorithms at the physical layer in the High-Speed Down-link Packet Access extension to WCDMA. Two different approaches to congestion control - TCP SACK and TFRC - are studied. We find that TCP SACK and TFRC in most respects perform the same way. SIR scheduling give a higher system throughput for both protocols than RR scheduling, but introduces delay variations that lead to spurious timeouts. The no feedback timeout of TFRC was shown to exhibit a similar sensitivity to delay spikes as the retransmit timeout in TCP SACK

  • 25.
    Bodin, Ulf
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Simonsson, Arne
    Ericsson Research, Luleå.
    Effects on TCP from radio-block scheduling in WCDMA high speed downlink shared channels2003Ingår i: Quality for all: 4th COST 263 International Workshop on Quality of Future Internet Services, QoFIS 2003, Stockholm, Sweden, October 1-2, 2003 : proceedings / [ed] Gunnar Klarlsson; Michael I. Smirnov, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2003, s. 214-223Konferensbidrag (Refereegranskat)
    Abstract [en]

    Avoiding delay jitter is essential to achieve high throughput for TCP. In particular, delay spikes can cause spurious timeouts. Such timeouts force TCP into slow-start, which may reduce congestion window sizes drastically. Consequently, there may not always be data available for transmission on bottleneck links. For HS-DSCH, jitter can occur due to varying interference. Also, properties of the radio-block scheduling influence the jitter. We evaluate, through simulations, effects on TCP from scheduling. Our evaluation shows that round-robin (RR) schedulers can give more jitter than SIR schedulers. SIR schedulers discriminates low SIR users to improve spectrum utilization while RR schedulers distribute transmission capacity fairly. The high jitter with RR scheduling cause however both lower utilization and decreased fairness in throughput among users than with SIR scheduling. The Eifel algorithm makes TCP more robust against delay spikes and reduces thereby these problems

  • 26.
    Karlsson, Johan
    et al.
    Luleå tekniska universitet.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Brodnik, Andrej
    Nilsson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Schelén, Olov
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Extended expedited forwarding: the in-time PHB group2003Ingår i: Computers and Communication, 2003. (ISCC 2003): Proceedings of the Eighth IEEE International Symposium on Computers and Communications, IEEE Computer Society Press , 2003, Vol. 1, s. 291-298Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a new set of forwarding behaviorsthat fits rate-adaptive and delay-sensitive applications withlimited loss tolerance. We consider an application to havelimited loss tolerance if it needs loss-free forwarding of specificpackets up to a certain rate. The new set of forwardingbehaviors are attractive for developing real-time applicationsfor the Internet. In particular, such applications canbe designed to use reserved forwarding capacity efficientlyand compete for more bandwidth while being fair to best-efforttraffic. To provide the new set of forwarding behaviors,we define a scheduling mechanism that can be implementedefficiently. Through simulations, we show that thismechanism supports the defined forwarding behaviors.

  • 27.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Quality issues in Internet packet forwarding2003Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis addresses quality issues in Internet Protocol (IP) packet forwarding. In IP networks, queue mechanisms and scheduling can be used to construct multiple forwarding behaviors. Thereby, both relative and independent services can be offered to Internet users. Independent services offer forwarding qualities known beforehand. Users are assumed to explicitly request admission to an independent service from their network provider. With relative services, users switch between these services to find one that provides an appealing balance between forwarding quality and cost. The thesis makes contributions to three research areas related to forwarding quality in IP networks; differentiating forwarding mechanisms, admission control for differentiated services, and forwarding quality in radio networks carrying Internet traffic. It contributes to the first research area with definitions of three recommendations related to offering loss-rate differentiation (i.e., multiple drop precedence levels). These recommendations are; (1) the total forwarding quality at congested links should not be degraded due to actions taken to create loss-rate differentiation, (2) traffic at high drop precedence levels should always be given a useful share of available forwarding resources, and (3) users should be able to predict the change in loss-rates when switching between drop precedence levels. We specify and evaluate properties of queue mechanisms following these recommendations. Also, as a contribution to the first research area, a new set of forwarding behaviors is specified and analyzed. These forwarding behaviors are suitable for rate-adaptive and delay-sensitive applications with limited loss-tolerance. Applications needing loss-free forwarding of specific packets can be said to have limited loss tolerance. We define and evaluate a scheduling mechanism creating these forwarding behaviors that can be implemented efficiently. The contribution to the second research area is a mechanism for admission control giving assurances on loss-rates to rate varying applications is defined. With this mechanism, dynamic per-link admission thresholds are used to limit committed aggregate rates. To allow for high link utilization through statistical multiplexing we specify a method to adjust these thresholds using low impact traffic monitoring mechanisms commonly available in legacy routers. In radio networks carrying IP traffic, radio transmissions can be scheduled differently to balance spectrum utilization and the forwarding quality provided. Also, parameters settings can be used to optimize the forwarding quality in radio networks for certain transport protocols and applications. This thesis analyses delay spikes experienced by IP traffic in cellular radio networks. We evaluate two different radio-block scheduling mechanisms’ impact on two versions of the Transmission Control Protocol (TCP) (i.e., TCP Sack and TCP Eifel). The evaluation contributes to the third research area by revealing basic dependencies between scheduling, interference, and congestion control mechanisms implemented by TCP. Finally, the thesis contributes to the third research area by proposing extensions to the Internet architecture for inter-layer communication. These extensions allow applications and transport protocols to exchange information with radio link layers. Such information exchange can be used to improve the forwarding quality and to customize data and transport features for current radio conditions.

  • 28. Larzon, Lars-Åke
    et al.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Schelén, Olov
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Hints and notifications [for wireless links]2002Ingår i: 2002 IEEE Wireless Communications and Networking Conference record: Orlando, Florida, USA, 17 - 21 March 2002, Piscataway, NJ: IEEE Communications Society, 2002, s. 635-641Konferensbidrag (Refereegranskat)
    Abstract [en]

    With current Internet protocols, users may experience low and unpredictable forwarding quality at wireless links. This is due to varying link properties caused by changing radio conditions. Decreased forwarding quality can cause severe degradation in utilization. This is undesirable since forwarding capacity often is expensive at wireless links because of the limited radio spectrum. Allowing the application and transport layers to communicate with wireless link layers can improve the forwarding quality and utilization. We propose to enable inter-layer communication by adding hints and notifications (HAN) to the Internet architecture. Hints can be introduced and used without notifications, while notifications need hints or a similar mechanism to operate. By using IP options and ICMP messages to implement HAN, a backward-compatible partial deployment is possible. With HAN, the network layer becomes truly wireless friendly and the radio spectrum can be used efficiently while supporting both real-time and traditional data applications.

  • 29.
    Bodin, Ulf
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Schelén, Olov
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Drop strategies and loss-rate differentiation2001Ingår i: Proceedings: Ninth International Conference on Network Protocols, ICNP 2001 : 11 - 14 November 2001, Riverside, California, USA, Los Alamitos, Calif: IEEE Communications Society, 2001, s. 146-154Konferensbidrag (Refereegranskat)
    Abstract [en]

    When offering loss-rate differentiation in IP networks, the drop strategy used can have a considerable influence on packet loss and delay. In particular, a strategy of dropping packets only as they arrive can cause bursty loss patterns and high jitter. When only arriving packets are dropped, the router may need to wait for low priority packets to arrive before dropping any packet. This results in larger queue oscillation than if low priority packets were dropped immediately from the queue. Queue oscillation gives bursty loss patterns and delay jitter. We present simulations showing that dropping packets from the queue gives smoother loss patterns and less jitter than if packets are dropped only as they arrive. These simulations cover both TCP Sack and TCP Reno. WRED with and without the gentle modification is used to make drop decisions.

  • 30.
    Bodin, Ulf
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Jonsson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Schelén, Olov
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    On creating proportional loss-rate differentiation: predictability and performance2001Ingår i: Quality of Service - IWQoS 2001: 9th International Workshop Karlsruhe, Germany, June 6-8, 2001 Proceedings / [ed] Lars Wolf, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2001, s. 372-386Konferensbidrag (Refereegranskat)
    Abstract [en]

    Recent extensions to the Internet architecture allow assignment of different levels of drop precedence to IP packets. This paper examines differentiation predictability and implementation complexity in creation of proportional lossrate (PLR) differentiation between drop precedence levels. PLR differentiation means that fixed loss-rate ratios between different traffic aggregates are provided independent of traffic loads. To provide such differentiation, running estimates of loss-rates can be used as feedback to keep loss-rate ratios fixed at varying traffic loads. In this paper, we define a loss-rate estimator based on average drop distances (ADDs). The ADD estimator is compared with an estimator that uses a loss history table (LHT) to calculate loss-rates. We show, through simulations, that the ADD estimator gives more predictable PLR differentiation than the LHT estimator. In addition, we show that a PLR dropper using the ADD estimator can be implemented efficiently.

  • 31.
    Bodin, Ulf
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Schelén, Olov
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Pink, Stephen
    Luleå tekniska universitet.
    Load-tolerant differentiation with active queue management2000Ingår i: Computer communication review, ISSN 0146-4833, E-ISSN 1943-5819, Vol. 30, nr 3, s. 4-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Current work in the IETF aims at providing service differentiation on the Internet. One proposal is to provide loss differentiation by assigning levels of drop procedence to IP packets. In this paper, we evaluate the active queue management (AQM) mechanisms RED In and Out (RIO) and Weighted RED (WRED) in providing levels of drop precedence under different loads. For low drop precedence traffic, FIO and WRED can be configured to offer sheltering (i.e., low drop precedence traffic is protected from losses caused by higher drop precedence traffic). However, if traffic control fails or is inaccurate, such configurations can cause starvation of traffic at high drop precedence levels. Configuring WRED to instead offer relative differentiation can eliminate the risk of starvation. However, WRED cannot, without reconfiguration, both offer sheltering when low drop precedence traffic is properly controlled and avoid starvation at overload of low drop precedence traffic. To achieve this, we propose a new AQM mechanism, WRED with Thresholds (WRT). The benefit of WRT is that, without reconfiguration, it offers sheltering when low drop precedence traffic is properly controlled and relative differentiation otherwise. We present simulations showing that WRT has these properties.

  • 32.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Queue mechanisms for differentiation in the Internet2000Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis addresses loss-rate differentiation in the Internet. Loss-rate differentiation can be offered by tagging packets with different levels of drop precedence. Multiple drop precedence levels can be used to provide relative service levels and to assure forwarding capacity in the Internet. Assured services offer forwarding qualities known beforehand. This makes them more predictable than relative services. Users are assumed to explicitly request an assured service from their network provider for traffic up to a specified rate. With relative service levels, users switch between these levels to find one that provides an appealing balance between forwarding quality and cost. The policy for drop precedence probabilities defines the type of loss-rate differentiation pro-vided. Sheltered loss-rate (SLR) differentiation is offered by strictly giving drops to traffic at high drop precedence levels. Sheltering means that traffic at a low drop precedence level is protected from losses caused by traffic at higher levels. Such protection is required for assured services. Relative loss-rate (RLR) differentiation is offered when drop precedence probabilities are rela-tively distributed between drop precedence levels. Offering fixed relations in these probabilities further refines RLR differentiation, resulting in proportional loss-rate (PLR) differentiation. This thesis defines three recommendations associated with providing loss-rate differentiation. Such differentiation can be created with queue mechanisms. We specify and evaluate the proper-ties of differentiating queue mechanisms that make them capable of meeting the recommenda-tions defined. These evaluations are made with simulations. Firstly, the total forwarding quality at congested links should not be degraded due to actions taken to create loss-rate differentiation. The total forwarding quality includes packet loss patterns and delay variations. These quality metrics are high when packet drops are delayed. When pro-viding loss-rate differentiation, drops can be delayed through only dropping packets as they ar-rive. Dropping packets from queues enables immediate drops. This thesis shows that with imme-diate drops less bursty loss patterns and lower delay variations are achieved than with delayed drops. Secondly, traffic at high drop precedence levels should always be given a useful share of avail-able forwarding resources. Such traffic may experience high loss-rates, but should not become starved. Traffic at high levels may become starved due to overloading of traffic at lower levels when creating SLR differentiation. Starvation can be avoided with proper control of low drop precedence traffic. This control may, however, fail due to changes in the network routing topol-ogy, inaccurate admission control, etc. To avoid starvation without relying on proper traffic con-trol, this thesis presents a new queuing mechanism that falls back from offering sheltering to providing RLR differentiation during overloading of low drop precedence traffic. Thirdly, PLR differentiation should be predictable. Users should be able to predict the change in loss-rates when switching between drop precedence levels. PLR differentiation requires relations in loss-rates to be fixed to pre-configured target ratios. Running estimates of loss-rate ratios can be used as feedback to adjust towards these targets if the actual loss-rate ratios deviate from the target ratios. To provide predictable PLR differentiation, these estimates need to be accurate and stable at varying traffic loads. Moreover, they need to detect traffic load variations rapidly. This thesis presents a loss-rate estimator that provides accurate, stable and rapid detection of loss-rate ratios at varying traffic loads.

  • 33.
    Palm, Emanuel
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Schelén, Olov
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Approaching Non-Disruptive Distributed Ledger TechnologiesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Distributed ledger technologies have been considered for a plethora of interesting use cases, ranging from supply chain integration to open medical journals. While able to facilitate novel forms of collaboration, the technologies also tend to break with existing business practices by imposing new requirements on cooperation governance, interaction privacy and contract making. In this paper, we identify distributed consensus algorithms and code-as-contracts as common causes of these paradigmatic divergences, and propose a system design that depends on neither of them. In particular, we present an experimental implementation of our Exchange Network architecture that uses a consensus procedure comparable to that of R3 Corda, but that models its interactions as negotiations about ownership exchanges rather than as function invocations and finite state machine transitions. Furthermore, we characterize the current cooperational paradigm and outline six requirements of adherence, as well as considering both how our own solution and how R3 Corda could fulfill them. We conclude that our design approach provides better opportunity for compatibility with conventional legal and business practices than the state-of-the-art.

1 - 33 av 33
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