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  • 1.
    Abrahamsson, H.
    et al.
    RISE, SICS, Germany.
    Abdesslem, F. B.
    RISE, SICS, Germany.
    Ahlgren, B.
    RISE, SICS, Germany.
    Brunstrom, A.
    Karlstad University, Sweden.
    Marsh, I.
    RISE, SICS, Germany.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Connected Vehicles in Cellular Networks: Multi-Access Versus Single-Access Performance2018Inngår i: TMA 2018 - Proceedings of the 2nd Network Traffic Measurement and Analysis Conference, Institute of Electrical and Electronics Engineers Inc. , 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Connected vehicles can make roads traffic safer and more efficient, but require the mobile networks to handle time-critical applications. Using the MONROE mobile broadband measurement testbed we conduct a multi-access measurement study on buses. The objective is to understand what network performance connected vehicles can expect in today's mobile networks, in terms of transaction times and availability. The goal is also to understand to what extent access to several operators in parallel can improve communication performance. In our measurement experiments we repeatedly transfer warning messages from moving buses to a stationary server. We triplicate the messages and always perform three transactions in parallel over three different cellular operators. This creates a dataset with which we can compare the operators in an objective way and with which we can study the potential for multi-access. In this paper we use the triple-access dataset to evaluate single-access selection strategies, where one operator is chosen for each transaction. We show that if we have access to three operators and for each transaction choose the operator with best access technology and best signal quality then we can significantly improve availability and transaction times compared to the individual operators. The median transaction time improves with 6% compared to the best single operator and with 61% compared to the worst single operator. The 90-percentile transaction time improves with 23% compared to the best single operator and with 65% compared to the worst single operator.

  • 2.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science, Kista, Sweden.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Caching for IPTV distribution with time-shift2013Inngår i: 2013 International Conference on Computing, Networking and Communications, ICNC 2013, IEEE , 2013, s. 916-921Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Today video and TV distribution dominate Internet traffic and the increasing demand for high-bandwidth multimedia services puts pressure on Internet service providers. In this paper we simulate TV distribution with time-shift and investigate the effect of introducing a local cache close to the viewers. We study what impact TV program popularity, program set size, cache replacement policy and other factors have on the caching efficiency. The simulation results show that introducing a local cache close to the viewers significantly reduces the network load from TV-on-Demand services. By caching 4% of the program volume we can decrease the peak load during prime time by almost 50%. We also show that the TV program type and how program popularity changes over time can have a big influence on cache hit ratios and the resulting link loads

  • 3.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Robust Traffic Engineering using L-balanced Weight-Settings in OSPF/IS-IS2009Inngår i: Proceedings of the 2009 6th International Conference on Broadband Communications, Networks and Systems, BROADNETS 2009, 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Internet traffic volumes continue to grow at a great rate, now pushed by video and TV distribution in the networks. This brings up the need for traffic engineering mechanisms to better control the traffic. The objective of traffic engineering is to avoid congestion in the network and make good use of available resources by controlling and optimising the routing function. The challenge for traffic engineering in IP networks is to cope with the dynamics of Internet traffic demands. Today, the main alternative for intra-domain traffic engineering in IP networks is to use different methods for setting the weights in the routing protocols OSPF and IS-IS. In this paper we revisit the weight setting approach to traffic engineering but with focus on robustness. We propose I-balanced weight settings that route the traffic on the shortest paths possible but make sure that no link is utilised to more than a given level I. This gives efficient routing of traffic and controlled spare capacity to handle unpredictable changes in traffic. We present a heuristic search method for finding I-balanced weight settings and show that it works well in real network scenarios

  • 4.
    Abrahamsson, Henrik
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Robust Traffic Engineering using L-balanced Weight-Settings in OSPF/IS-IS2008Annet (Annet vitenskapelig)
  • 5.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Simulation of IPTV caching strategies2010Inngår i: Proceedings of the 2010 International Symposium on Performance Evaluation of Computer and Telecommunication Systems, 2010, s. 187-193Konferansepaper (Fagfellevurdert)
    Abstract [en]

    IPTV, where television is distributed over the Internet Protocol in a single operator network, has become popular and widespread. Many telecom and broadband companies have become TV providers and distribute TV channels using multicast over their backbone networks. IPTV also means an evolution to time-shifted television where viewers now often can choose to watch the programs at any time. However, distributing individual TV streams to each viewer requires a lot of bandwidth and is a big challenge for TV operators. In this paper we present an empirical IPTV workload model, simulate IPTV distribution with time-shift, and show that local caching can limit the bandwidth requirements significantly.

  • 6.
    Ahmed, Mobyen Uddin
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Causevic, Aida
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Fotouhi, Hossein
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    An Overview on the Internet of Things for Health Monitoring Systems2016Inngår i: 2nd EAI International Conference on IoT Technologies for HealthCare HealthyIoT2015, 2016, Vol. 169, s. 429-436Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The aging population and the increasing healthcare cost in hospitals are spurring the advent of remote health monitoring systems. Advances in physiological sensing devices and the emergence of reliable low-power wireless network technologies have enabled the design of remote health monitoring systems. The next generation Internet, commonly referred to as Internet of Things (IoT), depicts a world populated by devices that are able to sense, process and react via the Internet. Thus, we envision health monitoring systems that support Internet connection and use this connectivity to enable better and more reliable services. This paper presents an overview on existing health monitoring systems, considering the IoT vision. We focus on recent trends and the development of health monitoring systems in terms of: (1) health parameters, (2) frameworks, (3) wireless communication, and (4) security issues. We also identify the main limitations, requirements and advantages within these systems.

  • 7.
    Ahmed, Mobyen Uddin
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    A Generic System-level Framework for Self-Serve Health Monitoring System through Internet of Things(IoT)2015Inngår i: Studies in Health Technology and Informatics, Volume 211: Proceedings of the 12th International Conference on Wearable Micro and Nano Technologies for Personalized Health, 2–4 June 2015, Västerås, Sweden, 2015, Vol. 211, s. 305-307Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Sensor data are traveling from sensors to a remote server, data is analysed remotely in a distributed manner, and health status of a user is presented in real-time. This paper presents a generic system-level framework for a self-served health monitoring system through the Internet of Things (IoT) to facilities an efficient sensor data management.

  • 8.
    Alderisi, Giuliana
    et al.
    University of Catania, Catania, Italy.
    Girs, Svetlana
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Lo Bello, Lucia
    University of Catania, Catania, Italy.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Probabilistic Scheduling and Adaptive Relaying for WirelessHART Networks2015Inngår i: 20th IEEE International Conference on Emerging Technologies and Factory Automation ETFA'15, 2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper deals with a way to probabilistically guarantee reliable packet delivery in WirelessHART based networks suitable for industrial control systems. We propose a new scheduling scheme, called Iterative Probabilistic Scheduling with Adaptive Relaying (IPS-AR), which consists of a static part (IPS) and a dynamic part (AR). IPS takes into account the channel characteristics and exploits relaying to achieve a minimum reliability threshold as requested by the supported industrial application. In the AR part, each relay node decides the packet to be sent based on online assessment of both the number of consecutive errors experienced by previous packets belonging to the same flow, as well as the number of copies of the packet currently available at the other relay nodes. This enables IPS-AR to achieve the desired reliability level while using the available re-sources in terms of time and bandwidth more efficiently.

  • 9.
    Aslam, Mudassar
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Gehrmann, Christian
    SICS Swedish ICT, Sweden.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    ASArP: Automated Security Assessment & Audit of Remote Platforms: using TCG-SCAP synergies2015Inngår i: Journal of Internet Services and Applications JISA-14, ISSN 1869-0238, Vol. 22, s. 28-39Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many enterprise solutions today are built upon complex distributed systems which are accessible to the users globally. Due to this global access, the security of the host platforms becomes critical. The platform administrators use security automation techniques such as those provided by Security Content Automation Protocol (SCAP) standards to protect the systems from the vulnerabilities that are reported daily; furthermore, they are responsible for keeping their systems compliant to the relevant security recommendations (governmental or industrial). Additionally, third party audit and certification processes are used to increase user trust in enterprise solutions. However, traditional audit and certification mechanisms are not continuous, that is, not frequent enough to deal with the daily reported vulnerabilities, and for that matter even auditors expect platform administrators to keep the systems updated. As a result, the end user is also forced to trust the platform administrators about the latest state of the platform. In this paper we develop an automated security audit and certification system (ASArP) which can be used by platform users or by third party auditors. We use security automation techniques for continuous monitoring of the platform security posture and make the results trustworthy by using trusted computing (TCG) techniques. The prototype development of ASArP validates the implementation feasibility; it also provides performance benchmarks which show that the ASArP based audit and certification can be done much more frequently (e.g. daily or weekly). The feasibility of ASArP based continuous audits is significantly better than traditional platform audits which are dependent on the physical presence of the auditors, thus making frequent audits much more expensive and operationally infeasible.

  • 10.
    Aslam, Mudassar
    et al.
    SICS Swedish ICT, Sweden.
    Gehrmann, Christian
    SICS Swedish ICT, Sweden.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Continuous Security Evaluation and Auditing of Remote Platforms by Combining Trusted Computing and Security Automation Techniques2013Inngår i: SIN 2013 - Proceedings of the 6th International Conference on Security of Information and Networks, 2013, s. 136-143Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In many new distributed systems paradigms such a cloud computing, Internet of Things (IoT), electronic banking, etc. the security of the host platforms is very critical which is managed by the platform owner. The platform administrators use security automation techniques such as those provided by Security Content Automation Protocol (SCAP) standards to ensure that the outsourced platforms are set up correctly and follow the security recommendations (governmental or industry). However, the remote platform users still have to trust the platform administrators. The third party security audits, used to shift the required user trust from the platform owner to a trusted entity, are scheduled and are not very frequent to deal with the daily reported vulnerabilities which can be exploited by the attackers. In this paper we propose a remote platform evaluation mechanism which can be used by the remote platform users themselves, or by the auditors to perform frequent platform security audits for the platform users. We analyze the existing SCAP and trusted computing (TCG) standards for our solution, identify their shortcomings, and suggest ways to integrate them. Our proposed platform security evaluation framework uses the synergy of TCG and SCAP to address the limitations of each technology when used separately

  • 11.
    Aslam, Mudassar
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Gehrmann, Christian
    Swedish Institute of Computer Science, Kista.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Security and Trust Preserving VM Migrations in Public Clouds2012Inngår i: Proceedings of the 11th IEEE International Conference onTrust, Security and Privacy in Computingand Communications (TrustCom-2012), IEEE Computer Society Digital Library, 2012, s. 869-876Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we consider the security and trustimplications of virtual machine (VM) migration from one cloudplatform to the other in an Infrastructure-as-a-Service (IaaS) cloud service model. We show how to extend and complement previous Trusted Computing techniques for secure VM launchto also cover the VM migration case. In particular, we propose a Trust_Token based VM migration protocol which guarantees that the user VM can only be migrated to a trustworthy cloud platform. Different from previous schemes, our solution is not dependent on an active (on-line) trusted third party. We show how our proposed mechanisms fulfill major security and trust requirements for secure VM migration in cloud environments.

  • 12.
    Aslam, Mudassar
    et al.
    Swedish Institute of Computer Science, Kista.
    Gehrmann, Christian
    Swedish Institute of Computer Science, Kista.
    Rasmusson, Lars
    Swedish Institute of Computer Science, Kista.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Securely Launching Virtual Machines on Trustworthy Platforms in a Public Cloud2012Inngår i: CLOSER 2012 - Proceedings of the 2nd International Conference on Cloud Computing and Services Science, 2012, s. 511-521Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we consider the Infrastructure-as-a-Service (IaaS) cloud model which allows cloud users to run their own virtual machines (VMs) on available cloud computing resources. IaaS gives enterprises the possibility to outsource their process workloads with minimal effort and expense. However, one major problem with existing approaches of cloud leasing, is that the users can only get contractual guarantees regarding the integrity of the offered platforms. The fact that the IaaS user himself or herself cannot verify the provider promised cloud platform integrity, is a security risk which threatens to prevent the IaaS business in general. In this paper we address this issue and propose a novel secure VM launch protocol using Trusted Computing techniques. This protocol allows the cloud IaaS users to securely bind the VM to a trusted computer configuration such that the clear text VM only will run on a platform that has been booted into a trustworthy state. This capability builds user confidence and can serve as an important enabler for creating trust in public clouds. We evaluate the feasibility of our proposed protocol via a full scale system implementation and perform a system security analysis.

  • 13.
    Barac, Filip
    et al.
    Mid Sweden University.
    Yu, Kan
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Gidlund, Mikael
    ABB, Corporate Research.
    Åkerberg, Johan
    ABB, Corporate Research.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Towards Reliable and Lightweight Communication in Industrial Wireless Sensor Networks2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we address the issues of timeliness and transmission reliability of existing industrial communication standards. We combine a Forward Error Correction coding schemeon the Medium Access Control layer with a lightweight routing protocol to form an IEEE 802.15.4-conformable solution, whichcan be implemented into already existing hardware without violating the standard. After laying the theoretical foundations,we conduct a performance evaluation of the proposed solution.The results show a substantial gain in reliability and reducedlatency, compared to the uncoded transmissions, as well ascommon Wireless Sensor Network routing protocols.

  • 14.
    Bergblomma, Marcus
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Ekström, Martin
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Ekström, Mikael
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Gerdtman, Christer
    Motion Control AB, Västerås, Sweden .
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik.
    A wireless low latency control system for harsh environments2012Inngår i: IFAC Proceedings Volumes (IFAC-PapersOnline): Vol. 11, PART 1, 2012, s. 17-22Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The use of wireless communication technologies in the industry offer severaladvantages. One advantage is the ability to deploy sensors where they previously could noteasily be deployed, for instance on parts that rotate. To use wireless communication in industrialcontrol loops, demands on reliability and latency requirements has to be met. This in anenvironment that may be harsh for radio communication. This work presents a reliable, lowlatency wireless communication system. The system is used in a wireless thyristor control loopin a hydro power plant generator. The wireless communication is based on Bluetooth radiomodules. The work shows a latency analysis together with empirical hardware based latencyand packet error rate measurements. The background noise of a hydro power plant station isalso investigated. The average latency between the Bluetooth modules for the proposed systemis 5.09 ms. The packet error rate is 0.00288 for the wireless low latency control system deployedin a hydro power plant.

  • 15.
    Bergblomma, Marcus
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Ekström, Martin
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Ekström, Mikael
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Garcia Castaño, Javier
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Wireless ECG network2009Inngår i: WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, VOL 25, PT 5, 2009, s. 244-247Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a time synchronized wireless ECG sensor network with reliable data communication. Wireless ECG systems are a popular research area where several research groups have presented point-to-point solutions. Alongside the wireless ECG research, the wireless sensor network research has created an increasing interest for secure, low power and predictable network applications. Combining these research areas is a natural step for the evolution of secure wireless monitoring of physiological parameters. In this study the Bluetooth radio standard has been chosen for its versatility. This paper focuses on both the hardware and the software development for a functional multihop ECG network using Bluetooth. The presented wireless ECG network is reliable up to link loss and is easily configured to send more or different types of signals. The system has been tested and verified for secure multihop communication.

  • 16.
    Björkman, Mats
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. ES (Embedded Systems).
    Cooperation between academia and industry within embedded sensor systems2018Inngår i: World Congress on Medical Physics and Biomedical Engineering IUPESM 2018, 2018, Vol. 68, nr 1Konferansepaper (Fagfellevurdert)
  • 17.
    Björkman, Mats
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Trådlösa sensornät i vård och omsorg2009Inngår i: Medicinteknikdagarna 2009, 2009Konferansepaper (Fagfellevurdert)
  • 18.
    Brahneborg, D.
    et al.
    Infoflex Connect AB, Stockholm, Sweden.
    Causevic, Adnan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Afzal, Wasif
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Towards a more reliable store-and-forward protocol for mobile text messages2018Inngår i: Proceedings of the Annual ACM Symposium on Principles of Distributed Computing, Association for Computing Machinery , 2018, s. 13-20Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Businesses often use mobile text messages (SMS) as a cost effective and universal way of communicating concise information to their customers. Today, these messages are usually sent via SMS brokers, which forward them further to the next stakeholder, typically the various mobile operators, and then the messages eventually reach the intended recipients. Infoflex Connect AB delivers an SMS gateway application to the brokers with the main responsibility of reliable message delivery within set quality thresholds. However, the protocols used for SMS communication are not designed for reliability and thus messages may be lost. In this position paper we deduce requirements for a new protocol for routing messages through the SMS gateway application running at a set of broker nodes, in order to increase the reliability. The requirements cover important topics for the required communication protocol such as event ordering, message handling and system membership. The specification of such requirements sets the foundation for the forthcoming design and implementation of such a protocol and its evaluation.

  • 19.
    Brahneborg, Daniel
    et al.
    Infoflex Connect AB, Stockholm, Sweden.
    Afzal, Wasif
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Causevic, Adnan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Daniel, Sundmark
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Round-Trip Time Anomaly Detection2018Inngår i: ICPE '18 Proceedings of the 2018 ACM/SPEC International Conference on Performance Engineering, 2018, s. 107-114Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Mobile text messages (SMS) are sometimes used for authentication, which requires short and reliable delivery times. The observed round-trip times when sending an SMS message provide valuable information on the quality of the connection. In this industry paper, we propose a method for detecting round-trip time anomalies, where the exact distribution is unknown, the variance is several orders of magnitude, and there are lots of shorter spikes that should be ignored. In particular, we show that using an adaption of Double Seasonal Exponential Smoothing to reduce the content dependent variations, followed by the Remedian to find short-term and long-term medians, successfully identifies larger groups of outliers. As training data for our method we use log files from a live SMS gateway. In order to verify the effectiveness of our approach, we utilize simulated data. Our contributions are a description on how to isolate content dependent variations, and the sequence of steps to find significant anomalies in big data.

  • 20. Ekelin, Svante
    et al.
    Nilsson, Martin
    Hartikainen, Erik
    Johnsson, Andreas
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Mångs, Jan-Erik
    Melander, Bob
    Björkman, Mats
    Real-time Measurement of End-to-End Available Bandwidth Using Kalman FilteringManuskript (Annet vitenskapelig)
  • 21.
    Ekelin, Svante
    et al.
    Mälardalens högskola, Institutionen för datavetenskap och elektronik. Ericsson Research, Stockholm, Sweden.
    Nilsson, Martin
    Ericsson Research, Stockholm, Sweden.
    Hartikainen, Erik
    Ericsson Research, Stockholm, Sweden.
    Johnsson, Andreas
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Mångs, Jan-Erik
    Ericsson Research, Stockholm, Sweden.
    Melander, Bob
    Ericsson Research, Stockholm, Sweden.
    Björkman, Mats
    Ericsson Research, Stockholm, Sweden.
    Real-time Measurement of End-to-End Available Bandwidth Using Kalman Filtering2006Inngår i: IEEE Symposium Record on Network Operations and Management Symposium2006,, 2006, s. 73-84Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a new method, BART (Bandwidth Available in Real-Time), for estimating the end-to-end available bandwidth over a network path. It estimates bandwidth quasi-continuously, in real-time. The method has also been implemented as a tool. It relies on self-induced congestion, and repeatedly samples the available bandwidth of the network path with sequences of probe packet pairs, sent at randomized rates. BART requires little computation in each iteration, is light-weight with respect to memory requirements, and adds only a small amount of probe traffic. The BART method uses Kalman filtering, which enables real-time estimation (a.k.a. tracking). It maintains a current estimate, which is incrementally improved with each new measurement of the inter-packet time separations in a sequence of probe packet pairs. The measurementmodel has a strong non-linearity, and would not at first sight be considered suitable for Kalman filtering, but we show how this non-linearity can be handled. BART may be tuned according to the specific needs of the measurement application, such as agility vs. stability of the estimate. We have tested an implementation of BART in a physical test network with carefully controlled cross traffic, with good accuracy and agreement. Testmeasurements have also been performed over the Internet. We compare the performance of BART with that of pathChirp, a state-of-the-art tool for measuring end-to-end available bandwidth in real-time. 

  • 22.
    Ekström, Martin
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Bergblomma, Marcus
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Ekström, Mikael
    Edith Cowan University, Bunbury, Australia.
    A Bluetooth Radio Energy Consumption Model for Low Duty-Cycle Applications2012Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 61, nr 3, s. 609-617Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a realistic model of the radio energy consumption for Bluetooth-equipped sensor nodes used in a low-duty-cycle network. The model is based on empirical energy consumption measurements of Bluetooth modules. This model will give users the possibility to optimize their radio communication with respect to energy consumption while sustaining the data rate. This paper shows that transmission power cannot always be directly related to energy consumption. Measurements indicate that, when the transmission power ranges from $-$5 to $+$10 dBm, the difference in consumed energy can be detected for each transmission peak in the sniff peak. However, the change is negligible for the overall energy consumption. The nonlinear behavior of the idle state for both master and slave when increasing the interval and number of attempts is presented. The energy consumption for a master node is in direct relation to the number of slaves and will increase by approximately 50% of the consumption of one slave per additional slave, regardless of the radio setting.

  • 23.
    Ekström, Martin
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Bergblomma, Marcus
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Ekström, Mikael
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Comparison study of ZigBee and Bluetooth with regards to power consumption, packet-error-rate and distanceManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    This paper present a empirical measurement comparison study of ZigBee and Bluetooth. The parameters investigated are power consumption, packet-error-rate or retransmissions and distance in different environments. This study shows the differences and similarities for the two different short range radio technologies. A measurement set-up and procedure that makes it possible to investigate power consumption of the radio module, retransmissions and packet-error-rate as well as ambient noise is presented. For both the Bluetooth and the ZigBee modules used in this study the distance itself have no influence of the power consumption. However the retransmission rate and packet-error-rate have a large influence on the power consumption. This study have show that the environment has a great impact on the range of the radio modules and the behaviour concerning the retransmission rate and packet-error-rate.

  • 24.
    Ekström, Martin
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Bergblomma, Marcus
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Ekström, Mikael
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Development of Programmable Micro Power Meter Testbed for Radio ModulesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    This paper presents the POMPOM testbed for high precision power consumption \textit{in situ} measurements for interchangeable radio modules.The main requirements for the development have been;

    Interchangeable radio modules to enable the same hardware testbed to be used independently of the radio standard used make comparison studies possible.

    The testbed should be programmable so that the need for hardware development should be minimized. The testbed must be able to act as a controller for the communication and simultaneously make accurate \textit{in situ} measurements of the energy consumption of the radio.

    The required sample rate must be at least 50 kSamples per second. The range of the current measurement should cover at least 0.2~$\mu$Ampere to 60~mAmpere with at least 14-bit resolution.

    Mobility, low cost and small size are vital for the testbed. It must be possible to deploy several measurement testbeds to act as sensor nodes in a wireless sensor network to capture the behavior of the entire network.

    The results for test measurement setup for POMPOM is presented to illustrate a typical usage of the testbed. The results presented show how the testbed can be used to investigate the correlation between distance, packet-error-rate and current consumption for a Zigbee radio.

  • 25.
    Ericsson, N.
    et al.
    SICS Swedish ICT, Västeras, Sweden.
    Lennvall, T.
    SICS Swedish ICT, Västeras, Sweden.
    Akerberg, J.
    ABB AB Corporate Research, Västeras, Sweden.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. IS (Embedded Systems).
    Challenges from research to deployment of industrial distributed control systems2016Inngår i: IEEE International Conference on Industrial Informatics (INDIN), 2016, s. 68-73Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A trend in the industrial domain is that the networks are growing and becoming more complex, this is further accelerated by the digitalization trend. In order to address this, there is a need to improve the efficiency when moving between the R&D phases. For example, integrate innovative research findings into industrial systems, shorten time to market, improve product quality and reduce the number of issues. Despite a huge research effort on network simulators and emulators there are still some issues that needs to be addressed. This paper presents challenges that needs to be resolved, in order for the industry to adopt and benefit from using network simulators and emulators. The major challenges streamlining the workflow in and between the different R&D phases while preserving the real-time aspects in the entire industrial distributed control system.

  • 26.
    Ericsson, N.
    et al.
    RISE SICS, Västerås, Sweden.
    Lennvall, T.
    RISE SICS, Västerås, Sweden.
    Åkerberg, Johan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Mats, Björkman
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    A flexible communication stack design for time sensitive embedded systems2017Inngår i: Proceedings of the IEEE International Conference on Industrial Technology, 2017, s. 1112-1117Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Trends like Internet of Things (IoT), 5G and Cloud are pushing for device connectivity to the Internet, which affects industrial embedded systems with e.g., an increase in code base and functionality. Due to different application requirements, there are relative little reuse between embedded systems with different run-time context (from super loop to multi-threaded), and different types of communication (best effort and real time). In order to improve code reuse and changeability, we propose a flexible communication stack design, that can be configured for time sensitive communication with a real-time operating system (RTOS), or configured for best effort communication with either a super loop or an operating system (OS). Experiments demonstrate the flexibility and simplicity of the design with different configurations, e.g., super loop, single threaded, multi-threaded. Measurements show that the variations in performance related to run-time context scales as expected. 

  • 27.
    Ericsson, Niclas
    et al.
    RISE SICS Västerås, Sweden.
    Lennvall, Tomas
    RISE SICS Västerås, Sweden.
    Åkerberg, Johan
    ABB AB Corporate Research, Sweden.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Custom simulation of Industrial Wireless Sensor and Actuator Network for improved efficiency during Research and Development2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Trends like the Cloud, Internet of Things and 5G are pushing for an increase in connectivity, but, introducing a new type of network in an industrial distributed control system is a big investment with high risks. Time to market with sufficient quality is crucial. However, when getting through the Research and Development (R&D) phases, a lot of time is spent on isolated activates, e.g., simulations, collecting requirements, design, coding, debugging, creating testbeds, and performing various tests. Therefore, there is a need to improve efficiency when moving between the R&D phases. For verification and validation of communication software, the most common network evaluation method in industry are real testbeds, mostly since a testbed can be very similar to the deployed system. Testbeds are, however, hard to debug and costly to maintain. Other network evaluation methods like simulators, have some strengths that testbeds are lacking, like repeatability, control over the network, and lower cost. However, code from simulators can seldom be reused, especially in industrial time-sensitive target systems, due to different abstraction levels, run-time behavior and system timing. This paper presents findings from a case study that targets improved efficiency, getting from research theories, to deployed devices in a homogeneous Industrial Wireless Sensor and Actuator Network (IWSAN). We propose a small subset of network simulators features which eases changeability, reuse, and debugging of communication software. The selected simulator features are evaluated with a proof of concept implementation that is customized to a research platform. The findings indicate improved efficiency when moving back and forth between activities in different R&D phases.

  • 28.
    Folke, Mia
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Hermans, Frederic
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Rodhe, Ioana
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Gunningberg, Per
    Mälardalens högskola, Akademin för innovation, design och teknik.
    A non-invasive, mobile system for lactate threshold estimation2011Inngår i: Medicinteknikdagarna 2011, Linkoping, Sweden, 2011Konferansepaper (Fagfellevurdert)
  • 29.
    Folke, Mia
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Hermans, Frederic
    Rodhe, Ioana
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Gunningberg, Per
    Mobile system for establishing the lactate threshold by analysing the respiratory air2011Konferansepaper (Fagfellevurdert)
  • 30.
    Fotouhi, Hossein
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Causevic, Adnan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Lundqvist, Kristina
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Communication and Security in Health Monitoring Systems - A Review2016Inngår i: Proceedings - International Computer Software and Applications Conference, 2016, s. 545-554Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The fast development of sensing devices and radios enables more powerful and flexible remote health monitoring systems. Considering the future vision of the Internet of Things (IoT), many requirements and challenges rise to the design and implementation of such systems. Bridging the gap between sensor nodes on the human body and the Internet becomes a challenging task in terms of reliable communications. Additionally, the systems will not only have to provide functionality, but also be highly secure. In this paper, we provide a survey on existing communication protocols and security issues related to pervasive health monitoring, describing their limitations, challenges, and possible solutions. We propose a generic protocol stack design as a first step toward handling interoperability in heterogeneous low-power wireless body area networks.

  • 31.
    Fotouhi, Hossein
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Causevic, Adnan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Vahabi, Maryam
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Interoperability in heterogeneous Low-Power Wireless Networks for Health Monitoring Systems2016Inngår i: 2016 IEEE International Conference on Communications Workshops, ICC 2016, 2016, s. 393-398Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Ensuring interoperability in the future Internet of Things applications can be a challenging task, especially in mission-critical applications such as Health Monitoring Systems. Existing low-power wireless network architectures are designed in isolated networks, and ensure a satisfying level of performance in homogeneous networks. However, with co-existence of different low-power networks, the interoperability related problems arise. To bridge this gap in this paper, we study various protocol stacks (i.e., Bluetooth, Bluetooth Low Energy, IEEE 802.15.4, ZigBee, 6LoWPAN and IEEE 802.15.6), and explain their specific features. Furthermore, we provide a generic protocol stack design that facilitates multiple radios with different protocol stacks, regardless of being IP-based or non-IP-based networks. We see this approach as a possibility to enhance network performance in terms of reliability, timeliness, and security, while providing higher levels of scalability and connectivity.

  • 32.
    Fotouhi, Hossein
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Vahabi, Maryam
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Rabet, Iliar
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Alves, Mário
    Politecnico do Porto, ISEP/IPP, Porto, Portugal.
    MobiFog: Mobility Management Framework for Fog-assisted IoT Networks2019Inngår i: IEEE Global Conference on Internet of Things GCIoT'19, 2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Mobility is becoming a challenging issue in upcoming IoT applications, where it is crucial to employ mobile entities. Patients with sensors attached to their body in health monitoring application, AGVs in industrial monitoring and factory automation applications, cars with several sensing devices in vehicular applications are a few examples of use cases with the need for mobile nodes. In parallel, Fog computing has revolutionized network architecture, while enabling local processing of measurements, and reducing bandwidth overhead, which results in a more reliable system and real-time support. However, mobility management is a missing framework within the mobile IoT networks with Fog computing architecture. This paper provides a simple and generic seamless handoff model, dubbed as MobiFog, where it addresses the handoff mechanism with zero delay, while providing high reliability.

  • 33.
    Fotouhi, Hossein
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Vahabi, Maryam
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Ray, Apala
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. ABB Corporate Research, India.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Reliable Communication in Health Monitoring Applications2016Inngår i: The 3rd EAI International Conference on IoT Technologies for HealthCare HealthyIoT'16, Västeraås, Sweden, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Remote health monitoring is one of the emerging IoT applications that has attracted the attention of communication and health sectors in recent years. We enable software defined networking in a wireless sensor network to provide easy reconfiguration and at run-time network management. In this way, we devise a multi-objective decision making approach that is implemented at the network intelligence to find the set of optimal paths that routes physiological data over a wireless medium. In this work, the main considered parameters for reliable data communication are path traffic, path consumed energy, and path length. Using multi-objective optimization technique within a case study, we find the best routes that provide reliable data communication.

  • 34.
    Fotouhi, Hossein
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Vahabi, Maryam
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Ray, Apala
    ABB Corporate Research, India.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    SDN-TAP: An SDN-based Traffic Aware Protocol for Wireless Sensor Networks2016Inngår i: 18th International Conference on e-Health Networking, Applictions and Services Healthcom'16, 2016, artikkel-id 7749527Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Congestion control is a challenging issue in wireless sensor networks with limited channel bandwidth. Thus, many protocols have been designed to provide a distributed traffic control during packet forwarding. However, all these approaches are applied to single-hop communication networks, ignoring the multi-hop restrictions. In this work, we take advantage of software defined networking paradigm by devising a controller node in such a way that it collects all the necessary information from wireless sensor network nodes. Thus, based on hop count and local traffic information, controller decides for possible flow path changes to evenly distribute the traffic. The evaluations revealed that the SDN-TAP outperforms conventional routing protocols by reducing packet loss rate up to 46%.

  • 35.
    Fotouhi, Hossein
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Vahabi, Maryam
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Tomasic, Ivan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Petrovic, Nikola
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. ES (Embedded Systems).
    IPv6 connectivity in eHealth IoT networks2018Inngår i: Medicinteknikdagarna 2018 MTD 2018, Umeå, Sweden, 2018Konferansepaper (Fagfellevurdert)
  • 36.
    Gardasevic, Gordana
    et al.
    University of Banja Luka, Bosnia-Herzegovina.
    Fotouhi, Hossein
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Tomasic, Ivan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Vahabi, Maryam
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    A Heterogeneous IoT-based Architecture for Remote Monitoring of Physiological and Environmental Parameters2018Inngår i: Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST, Volume 225, 2018, s. 48-53Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A heterogeneous Internet of Things (IoT) architecture for remote health monitoring (RHM) is proposed, that employs Bluetooth and IEEE 802.15.4 wireless connectivity. The RHM system encompasses Shimmer physiological sensors with Bluetooth radio, and OpenMote environmental sensors with IEEE 802.15.4 radio. This system architecture collects measurements in a relational database in a local server to implement a Fog node for fast data analysis as well as in a remote server in the Cloud. 

  • 37.
    Girs, Svetlana
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Bergblomma, Marcus
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. Halmstad University, Sweden.
    Štimac, Barbara
    University of Zagreb, Zagreb, Croatia .
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Design of Channel Measurement Guidelines for Characterization of Wireless Industrial Environments2013Rapport (Annet vitenskapelig)
    Abstract [en]

    Providing reliable and timely communication in wireless industrial systems requires careful design of error control schemes able to tackle the bit error patterns typically occurring in these environments. As most error control schemes target some specific characteristics of a wireless channel, the selection of channel model is crucial for proper performance assessment. There are a number of widely used channel models, but the question of the most appropriate choice of model for industrial environments still remains largely open. Not many indoor measurement campaigns have focused on industrial environments with their own specific characteristics. In this paper we present a set of measurement guidelines aiming to characterize industrial environments such that suitable channel models can be selected to properly evaluate error control schemes targeting reliable and timely wireless communications in industrial environments. 

  • 38.
    Girs, Svetlana
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Adopting FEC and Packet Combining to Increase the Performance of IWSNs Using Relaying2015Inngår i: International Conference on Computing and Network Communications CoCoNet'15, 2015, s. 90-97Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Industrial networks can benefit significantly from introduction of wireless communication. However, wireless systems suffer from much higher packet error rates than wired networks do, making it difficult to obtain sufficient reliability within application deadlines. One promising approach to increase the reliability of wireless communication systems without causing excessive additional delays is to exploit spatial diversity. However, often in industrial networks it is not possible to place the relay nodes optimally. Due to this not even relay nodes located close to the source are able to receive the source packets missing at the destination correctly and consequently they cannot assist by relaying. Therefore, to benefit even further from relaying, additional measures should be taken both to increase the number of the correct packets at the relay nodes and to allow the destination to recover more correct packets. Consequently, the focus of this work is schemes enabling relaying, forward-error-correction (FEC) and packet combining without causing additional delays or complexity such that it is possible to use off the shelf transceivers. The results show that the introduction of FEC and packet combining does improve performance by enabling relay nodes to help more often. However, the exact gain depends on the specific FEC scheme used and, in particular, the size of the preamble and other fields that must be left uncoded, but still be received correctly, to be able to use FEC on the received packet.

  • 39.
    Girs, Svetlana
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. Halmstad University.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Increased Reliability of Reduced Delay in Wireless Industrial Networks Using Relaying and Luby Codes2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Providing reliable and timely communication in wireless industrial networks is crucial. Previous research has shown that relaying can aid in achieving this goal. We consider the case when relay resources are sparse such that each relay needs to aid e.g., three different sensor nodes and propose to combine relaying with Luby codes. We let the relay node construct a Luby coded packet using the three source packets as input. The destination can then use the Luby coded packet to recover an erroneous or lost source packet regardless of which source that packet belonged to. The performance evaluation shows that our proposed scheme significantly increases the number of correctly received packets before the corresponding deadlines, or alternatively that high reliability can be maintained even if fewer time slots are allocated for retransmissions, thus lowering the delay.

  • 40.
    Girs, Svetlana
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Uhlemann, Elisabeth
    Halmstad University.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    The Effects of Relay Behavior and Position in Wireless Industrial Networks2012Inngår i: 2012 9th IEEE International Workshop on Factory Communication Systems, May 21-24, 2012 Lemgo, Germany: Proceedings, 2012, s. 183-190Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In wireless industrial networks, providing reliable and timely communication is crucial. Previous research has shown that relaying can be used to achieve this goal. However, we have found that different types of wireless channels encountered in industrial environments affect the benefits as well as the best behavior and position of relay nodes. We consider two types of behavior: the relay node always retransmits or it only retransmits if it has obtained a correct copy of the packet. We evaluate different positions of the relay node by conducting simulations for two types of fading channels: with and without line of sight. The results clearly show that the benefits, the best behavior and position of a relay node depends on the wireless channel, whether or not the bit errors appear randomly or in bursts and also on the distance between the source and the final destination.

  • 41.
    Girs, Svetlana
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Willig, Andreas
    University of Canterbury, Canterbury, New Zealand.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. Halmstad University, Halmstad, Sweden.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    On the Role of Feedback for Industrial Networks Using Relaying and Packet Aggregation2013Rapport (Annet vitenskapelig)
    Abstract [en]

    To be accepted for use in industrial applications, wireless technologies must offer similar performance in terms of reliability and timeliness as provided by current wired solutions. Wireless channels, introducing time-varying packet error rates, impose a significant challenge to fulfill these requirements. One way to improve reliability in industrial wireless networks is to use relaying, whereas packet aggregation is a method that can reduce delay. Hence, in this paper, we propose to use a combination of relaying and packet aggregation. Based on the type of feedback provided by the controller, the relay node can choose the most suitable way to use its allocated time slots such that more packets can reach the controller before their deadlines. The results show that allowing this kind of flexibility at the relay node results in performance improvements. The more flexibility, the greater the gain, and thus further improvements can be made by adjusting the schedule to take different types of feedback into account.

  • 42.
    Girs, Svetlana
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Willig, Andreas
    University of Canterbury, UK.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. Halmstad University.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Scheduling for source relaying with packet aggregation in industrial wireless networks2016Inngår i: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 12, nr 5, s. 1855-1864Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interest in wireless communication systems for industrial applications has grown significantly over the last years. More flexible, easier to install and maintain, wireless networks present a promising alternative to the currently used wired systems. However, reliability and timeliness requirements at present met by wired networks also need to be fulfilled by wireless solutions. Packet errors introduced when packets travel through wireless channels imply a significant challenge to fulfill these requirements. Relaying has been recognized to improve the reliability in industrial wireless networks without causing additional delay. Furthermore, the recent results have shown that relaying combined with packet aggregation significantly outperforms simple relaying. However, it is not always cost efficient to introduce additional relay nodes into an industrial network and hence, in this paper, we propose using a combination of relaying and packet aggregation at the source nodes. The results show that when relaying and aggregation are used at the source nodes, the transmission schedule plays a crucial role. A schedule adapting to the varying channel conditions improves performance substantially. By carefully choosing which packet to aggregate, even further improvements can be achieved.

  • 43.
    Girs, Svetlana
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Willig, Andreas
    University of Canterbury, Canterbury, New Zealand.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. Halmstad University, Halmstad, Sweden .
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Scheduling transmissions in industrial networks using source relaying and packet aggregation2015Inngår i: 11th IEEE World Conference on Factory Communication Systems WFCS'15, 2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Wireless networks present a promising alternative to the currently used wired systems as they are more flexible, easier to install and maintain. However, requirements on reliability and timeliness which at present are met by wired networks, also need be fulfilled by wireless solutions.Relaying and packet aggregation have been recognised as viable tools to do this. However, introducing additional relay nodes into an industrialnetwork is costly. Hence, in this paper we propose to use a combination of relaying and packet aggregation performed by the source nodes themselves. The results show that our proposal improves performance considerably, but also that the transmission schedule plays a crucial role. A schedule adapting to the varying channel conditions, improves the performance substantially. By carefully choosing which packet to aggregate, even further improvements can be achieved.

  • 44.
    Gutiérrez Peón, Pablo
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. TTTech Computertechnik AG, Vienna, Austria.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Steiner, Wilfried
    TTTech Computertechnik AG, Vienna, Austria.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    A Wireless MAC Method with Support for Heterogeneous Data Traffic2015Inngår i: IECON 2015 - 41st Annual Conference of the IEEE Industrial Electronics Society, 2015, s. 3869-3874, artikkel-id 7392703Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An important aspect of any communication technology is its medium access method, being responsible for sharing the medium among users. For delay-sensitive applications, such as industrial control systems, timely and reliable channel access is of essence. Hence, existing protocols like HART and TTEthernet use a time-triggered medium access approach. However, as the nature of industrial control systems change and evolve, there is a growing need to provide wireless access and support data traffic with mixed requirements. While technologies like WirelessHART can offer timely and reliable access to the wireless medium, only one type of data traffic is usually supported. In this paper, we therefore propose and evaluate three different medium access methods for wireless communications, all capable of supporting three different data traffic classes: time-triggered, rate-constrained and best-effort traffic. In particular, different options on how to handle best-effort traffic, using scheduled time-slots or contention, are evaluated, showing for all the proposals different drawbacks and benefits depending on additional requirements on e.g., hardware, protocol overhead and resistance to interference.

  • 45.
    Gutiérrez Peón, Pablo
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. TTTech Computertechnik AG, Vienna, Austria.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Steiner, Wilfried
    TTTech Computertechnik AG, Vienna, Austria.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Applying Time Diversity for Improved Reliability in a Real-Time Heterogeneous MAC Protocol2017Inngår i: 2017 IEEE 85TH VEHICULAR TECHNOLOGY CONFERENCE (VTC SPRING), 2017, artikkel-id 8108663Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Supporting real-time applications over wireless networks is challenging for several reasons. The medium access control (MAC) layer has a key role in enabling real-time guarantees by providing bounded access time to the transmission medium. Unfortunately, even when timely access is granted, transmissions can still be compromised, specially in the wireless domain, due to the unreliable transmission medium. A common way to increase the reliability of a communication system is to apply redundancy in the form of time diversity, i.e., transmitting several copies of the same message at different points in time. In this paper we propose a wireless MAC protocol capable of handling traffic with different levels of criticality and where transmissions and retransmissions are tailored to deadlines, so that the reliability of the communication system is increased and real-time guarantees can be provided. We focus on the traffic scheduling problem, and extend an already existing solution, Time-Triggered Ethernet, suitable for real-time traffic over wired multi-hop networks. The extension enables transmission of heterogeneous traffic over hybrid wired-wireless networks, and provides timely retransmissions in the wireless segment, such that the real-time guarantees are met. Further, we are able to schedule traffic to better cope with interference patterns of different duration, frequency and level of persistence. The results show that the MAC protocol can be successfully applied to combat different kinds of interference while meeting real-time deadlines.

  • 46.
    Gutiérrez Peón, Pablo
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Steiner, Wilfried
    TTTech Computertechnik AG, Austria.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Applying Time Diversity for Improved Reliability in a Real-Time Wireless MAC Protocol2016Rapport (Annet vitenskapelig)
    Abstract [en]

    Supporting real-time applications over wireless networks is challenging for several reasons. However, the inherent advantages due to wireless access like reduced wiring or the possibility to transmit between moving components are still desirable in many application domains. In particular, wireless support to applications with traffic having diverse time and safety requirements is desirable. The medium access control (MAC) layer plays a key role in enabling real-time guarantees, since it provides access to the transmission medium. Unfortunately, even if timely access is guaranteed, transmissions can still be compromised due to the unreliable wireless medium. A common way to increase the reliability of a communication system is to apply redundancy in the form of time diversity, i.e., transmitting several copies of the same message at different points in time. In this paper we propose a wireless MAC method in where transmissions and retransmissions are tailored to deadlines, so that the reliability of the communication system is increased and real-time guarantees can be provided. The proposal enables coexistence of three different traffic classes: time-triggered, rate-constrained and best-effort. Further, we have analysed the effect of different protocol configurations subject to interference with different duration, frequency, and level of persistence. The results show that different protocol settings can be successfully applied to combat different kinds of interference to improve transmission reliability and timeliness.

  • 47.
    Gutiérrez Peón, Pablo
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Steiner, Wilfried
    TTTech Computertechnik AG.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Medium Access Control for Wireless Networks with Diverse Time and Safety Real-Time Requirements2016Inngår i: 42nd Annual Conference of the IEEE Industrial Electronics Society IECON 2016, 2016, s. 4665-4670, artikkel-id 7794095Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The communication in-between embedded systems present in cars and planes, requires real-time networks. Up to now, fieldbus technologies like PROFIBUS and CAN have covered the demand for predictable communications in embedded systems. However, these fieldbuses do not suit some of the emerging application domains, that need more flexibility, support for dynamic traffic flows, different traffic classes, high throughput, and the inclusion of wireless capabilities. To this end, we propose several different medium access control (MAC) schemes with support for traffic with diverse time and safety requirements. We have calculated the worst case channel access delay for each proposal, and also simulated them in OMNeT++ to analyse and compare their performance in terms of average access delay and packet collisions as a function of different protocol settings and traffic patterns e.g., the channel load, data traffic emerging from one sender only versus evenly distributed between all senders. Our results indicate that the more that is known about the data traffic, the better performance can be achieved by selecting an appropriate MAC protocol. Conversely, when nothing is known, one MAC protocol emerges as the best trade-off.

  • 48.
    Hagos Yitbarek, Yonas
    et al.
    Chalmers University of Technology, Sweden .
    Yu, Kan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Åkerberg, Johan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Gidlund, Mikael
    ABB AB, Corporate Research, Sweden .
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Implementation and Evaluation of Error Control Schemes in Industrial Wireless Sensor Networks2014Inngår i: Proceedings of the IEEE International Conference on Industrial Technology, 2014, s. 730-755Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Industrial Wireless Sensor Networks (IWSNs) have been increasingly adopted in process automation due to a number of advantages such as cost reduction and enhanced flexibility. Nevertheless, transmission over wireless channels in industrial environments is prone to interference, resulting in frequent erroneous packet deliveries. Existing IWSN standards based on the IEEE 802.15.4 specification only prescribe Automatic Repeat Request (ARQ) for packet retransmission, without providing any means for error recovery, which leads to unexpected transmission delay. Forward Error Correction (FEC) code as an alternative approach is able to effectively improve reliability and reduce the number of retransmissions. However, FEC computation requires extra memory and processing time. In this paper, we discuss the timing constraints of employing FEC codes for IWSNs according to the IWSN standards. Then we benchmark a number of different FEC codes in a typical wireless sensor node in terms of memory consumption and processing time. Our results show that LDPC and Turbo code, as the state of the art FEC codes, fail to fulfill the requirement from the IWSN standards while other FEC candidates, such as RS code, are proven to be suitable for the practical implementation in IWSNs.

  • 49.
    Hansen, Ewa
    et al.
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Neander, Jonas
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Nolin, Mikel
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Björkman, Mats
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Energy-Efficient Cluster Formation for Large Sensor Networks using a Minimum Separation Distance2006Inngår i: In proceedings of the Fifth Annual Mediterranean Ad Hoc Networking Workshop, 2006Konferansepaper (Fagfellevurdert)
  • 50.
    Hansen, Ewa
    et al.
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Neander, Jonas
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Sjödin, Mikael
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Björkman, Mats
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Efficient Cluster Formation for Sensor Networks2006Rapport (Annet vitenskapelig)
    Abstract [en]

    The interest in wireless sensor networks is growing and the development of energy efficient infrastructures for such networks is becoming increasingly important.

    In this paper we investigate the usefulness of enforcing a minimum separation distance between cluster heads in a cluster based sensor network, i.e. prolonging network lifetime by lowering the energy consumption.

    The simulations where performed in order to determine how much we can lower the energy consumption in the sensor network by separating the cluster heads. We have also investigated how the number of clusters affect the energy consumption for a given minimum separation distance.

    We show that our sensor network performs up to 150\% better when introducing a minimum separation distance between cluster heads, comparing the number of messages received at the base station.

    The simulations also show that the minimum separation distance that result in the lowest energy consumption in our network varies with the number of clusters.

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