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  • 1.
    Alderisi, Giuliana
    et al.
    University of Catania, Catania, Italy.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Lo Bello, Lucia
    University of Catania, Catania, Italy.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Probabilistic Scheduling and Adaptive Relaying for WirelessHART Networks2015In: 20th IEEE International Conference on Emerging Technologies and Factory Automation ETFA'15, 2015Conference paper (Refereed)
    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.

  • 2.
    Balador, Ali
    et al.
    SICS Swedish ICT Västerås AB, Sweden.
    Böhm, Annette
    Halmstad University, Sweden.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Calafate, Carlos T.
    Universitat Politecnica de Valencia, Spain.
    Cano, Juan-Carlos
    Universitat Politecnica de Valencia, Spain.
    A Reliable and Efficient Token-Based MAC Protocol for Platooning Applications2016In: 12th Swedish National Computer Networking Workshop SNCNW 2016, 2016Conference paper (Refereed)
    Abstract [en]

    Platooning is both a challenging and rewarding application. Challenging since strict timing and reliability requirements are imposed by the distributed control system required to operate the platoon. Rewarding since considerable fuel reductions are possible. As platooning takes place in a vehicular ad hoc network, the use of IEEE 802.11p is close to mandatory. However, the 802.11p medium access method suffers from packet collisions and random delays. Most ongoing research suggests using TDMA on top of 802.11p as a potential remedy. However, TDMA requires synchronization and is not very flexible if the beacon frequency needs to be updated, the number of platoon members changes, or if retransmissions for increased reliability are required. We therefore suggest a token-passing medium access method where the next token holder is selected based on beacon data age. This has the advantage of allowing beacons to be re-broadcasted in each beacon interval whenever time and bandwidth are available. We show that our token-based method is able to reduce the data age and considerably increase reliability compared to pure 802.11p.

  • 3.
    Balador, Ali
    et al.
    Universitat Politecnica de Valencia, Spain.
    Böhm, Annette
    Halmstad University, Sweden.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Calafate, Carlos T.
    Universitat Politecnica de Valencia, Spain.
    Cano, Juan-Carlos
    Universitat Politecnica de Valencia, Spain.
    A reliable token-based MAC protocol for delay sensitive platooning applications2015In: 2015 IEEE 82nd Vehicular Technology Conference, VTC Fall 2015 - Proceedings, Boston, MA, United States, 2015, p. Article number 7390813-Conference paper (Refereed)
    Abstract [en]

    Platooning is both a challenging and rewarding application. Challenging since strict timing and reliability requirements are imposed by the distributed control system required to operate the platoon. Rewarding since considerable fuel reductions are possible. As platooning takes place in a vehicular ad hoc network, the use of IEEE 802.11p is close to mandatory. However, the 802.11p medium access method suffers from packet collisions and random delays. Most ongoing research suggests using TDMA on top of 802.11p as a potential remedy. However, TDMA requires synchronization and is not very flexible if the beacon frequency needs to be updated, the number of platoon members changes, or if retransmissions for increased reliability are required. We therefore suggest a token-passing medium access method where the next token holder is selected based on beacon data age. This has the advantage of allowing beacons to be re-broadcasted in each beacon interval whenever time and bandwidth are available. We show that our token-based method is able to reduce the data age and considerably increase reliability considerably compared to pure 802.11p.

  • 4.
    Balador, Ali
    et al.
    Polytechnic University of Valencia, Valencia, Spain.
    Böhm, Annette
    Halmstad Universit, Sweden.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Calafate, Carlos T.
    Polytechnic University of Valencia, Valencia, Spain.
    Ji, Yusheng
    National Institute of Informatics, Tokyo, Japan.
    Cano, Juan-Carlos
    Polytechnic University of Valencia, Valencia, Spain.
    Manzoni, Pietro
    Polytechnic University of Valencia, Valencia, Spain.
    An Efficient MAC Protocol for vehicle platooning in automated highway systems2015In: Jornadas Sarteco 2015 JS 2015, Cordoba, Spain, 2015Conference paper (Refereed)
    Abstract [en]

    Lately, all the top truck manufacturers are investing considerable resources in the research and development of platooning systems which would allow vehicles to save fuel and improve safety by travelling in a close-following manner. The platoon-ing system requires frequent and reliable vehicle-to-vehicle communications. As platooning takes place in a vehicular ad hoc network, the use of IEEE 802.11p is close to mandatory. However, the 802.11p medium access method suffers from packet collisions and random delays. Most ongoing research suggests using TDMA on top of 802.11p as a potential remedy. However , TDMA requires synchronization and is not very flexible if the beacon frequency needs to be updated, the number of platoon members changes, or if re-transmissions for increased reliability are required. We therefore suggest a token-passing medium access method where the next token holder is selected based on beacon data age. This has the advantage of allowing beacons to be re-broadcasted in each beacon interval whenever time and bandwidth are available. We show that our token-based method is able to reduce the data age and considerably increase reliability considerably compared to pure 802.11p.

  • 5.
    Balador, Ali
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Calafate, C. T.
    Universitat Politècnica de València, València, Spain.
    Cano, J. -C
    Universitat Politècnica de València, València, Spain.
    Supporting beacon and event-driven messages in vehicular platoons through token-based strategies2018In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 18, no 4, article id 955Article in journal (Refereed)
    Abstract [en]

    Timely and reliable inter-vehicle communications is a critical requirement to support traffic safety applications, such as vehicle platooning. Furthermore, low-delay communications allow the platoon to react quickly to unexpected events. In this scope, having a predictable and highly effective medium access control (MAC) method is of utmost importance. However, the currently available IEEE 802.11p technology is unable to adequately address these challenges. In this paper, we propose a MAC method especially adapted to platoons, able to transmit beacons within the required time constraints, but with a higher reliability level than IEEE 802.11p, while concurrently enabling efficient dissemination of event-driven messages. The protocol circulates the token within the platoon not in a round-robin fashion, but based on beacon data age, i.e., the time that has passed since the previous collection of status information, thereby automatically offering repeated beacon transmission opportunities for increased reliability. In addition, we propose three different methods for supporting event-driven messages co-existing with beacons. Analysis and simulation results in single and multi-hop scenarios showed that, by providing non-competitive channel access and frequent retransmission opportunities, our protocol can offer beacon delivery within one beacon generation interval while fulfilling the requirements on low-delay dissemination of event-driven messages for traffic safety applications. 

  • 6.
    Bello, L. L.
    et al.
    University of Catania, Catania, Italy.
    Åkerberg, J.
    ABB Corporate Research, Västerås, Sweden.
    Gidlund, M.
    Mid Sweden University, Sundsvall, Sweden.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Guest Editorial Special Section on New Perspectives on Wireless Communications in Automation: From Industrial Monitoring and Control to Cyber-Physical Systems2017In: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 13, no 3, p. 1393-1396, article id 7938563Article in journal (Refereed)
  • 7.
    Bilstrup, Katrin
    et al.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Böhm, Annette
    Högskolan i Halmstad, Inbyggda system (CERES).
    Lidström, Kristoffer
    Högskolan i Halmstad, Inbyggda system (CERES).
    Jonsson, Magnus
    Högskolan i Halmstad, Inbyggda system (CERES).
    Larsson, Tony
    Högskolan i Halmstad, Inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Report on the Collaboration between CVIS and CERES in the Project Vehicle Alert System (VAS)2009Report (Other academic)
    Abstract [en]

    In March 2007, an agreement was made for interchange of experiences between CVIS and the Centre for Research on Embedded Systems (CERES) at Halmstad University in Sweden. The majority of the work relating to this collaboration has been conducted within the CERES project Vehicle Alert System (VAS), aiming to use vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications to provide different types of warning messages. The main focus of the VAS project is on communication and in particular the lower layers of the communication stack are investigated. VAS involves academic researchers from Halmstad University as well as researchers from Volvo Technology, SP Technical Research Institute of Sweden and the company Free2move. This report presents the results of the VAS project, its publications, and other issues of interest both to the CVIS consortium as well as a broader scope.

  • 8.
    Bilstrup, Katrin
    et al.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Ström, Erik G.
    Chalmers.
    Medium access control in vehicular networks based on the upcoming IEEE 802.11p standard2008In: 15th World Congress on Intelligent Transport Systems and ITS America Annual Meeting 2008, World Congress on ITS , 2008, p. 4155-4167Conference paper (Refereed)
    Abstract [en]

    In this paper, initial simulations are presented showing that the upcoming IEEE 802.11p standard is not suitable for traffic safety applications requiring reliable, low delay communication between vehicles. The medium access control procedure is one of the most important parts in the design of delay-constrained communication systems, and emerging vehicle safety applications put new stringent demands on timely and reliable delivery of data packets. The medium access procedure used in 802.11p is carrier sense multiple access, which is inherently unsuitable for time-critical data traffic since it is contention-based and cannot provide a finite upper bound on the time to channel access. The simulation results indicate that with IEEE 802.11p, channel access cannot be granted in a manner that is sufficiently predictable to support reliable, low-delay communications between vehicles on a highway.

  • 9.
    Bilstrup, Katrin
    et al.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Ström, Erik G.
    Chalmers.
    Bilstrup, Urban
    Högskolan i Halmstad, Inbyggda system (CERES).
    Evaluation of the IEEE 802.11p MAC method for vehicle-to-vehicle communication2008In: 68th IEEE Vehicular Technology Conference, 2008. VTC 2008-Fall: IEEE Vehicular Technology Conference (VTC) (2008), Piscataway, N.J.: IEEE Press , 2008, p. Article number 4657278-Conference paper (Refereed)
    Abstract [en]

    In this paper the medium access control (MAC) method of the upcoming vehicular communication standard IEEE 802.11p has been simulated in a highway scenario with periodic broadcast of time-critical packets (so-called heartbeat messages) in a vehicle-to-vehicle situation. The 802.11p MAC method is based on carrier sense multiple access (CSMA) where nodes listen to the wireless channel before sending. If the channel is busy, the node must defer its access and during high utilization periods this could lead to unbounded delays. This well-known property of CSMA is undesirable for time critical communications. The simulation results reveal that a specific node/vehicle is forced to drop over 80% of its heartbeat messages because no channel access was possible before the next message was generated. To overcome this problem, we propose to use self-organizing time division multiple access (STDMA) for real-time data traffic between vehicles. This MAC method is already successfully applied in commercial surveillance applications for ships (AIS) and airplanes (VDL mode 4). Our initial results indicate that STDMA outperforms CSMA for time-critical traffic safety applications in ad hoc vehicular networks.

  • 10.
    Bilstrup, Katrin
    et al.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Ström, Erik G.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Bilstrup, Urban
    Högskolan i Halmstad, Inbyggda system (CERES).
    On the ability of the 802.11p MAC method and STDMA to support real-time vehicle-to-vehicle communications2009In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 2009, no 902414, p. 1-14Article in journal (Refereed)
    Abstract [en]

    Traffic safety applications using vehicle-to-vehicle (V2V) communication is an emerging and promising area within the intelligent transportation systems (ITS) sphere. Many of these new applications require real-time communication with high reliability, meaning that packets must be successfully delivered before a certain deadline. Applications with early deadlines are expected to require direct V2V communications, and the only standard currently supporting this is the upcoming IEEE 802.11p, included in the wireless access in vehicular environment (WAVE) stack. To meet a real-time deadline, timely and predictable access to the channel is paramount. However, the medium access method used in 802.11p, carrier sense multiple access with collision avoidance (CSMA/CA), does not guarantee channel access before a finite deadline. In this paper, we analyze the communication requirements introduced by traffic safety applications, namely, low delay, reliable, real-time communications.We show by simulation of a simple, but realistic, highway scenario, that vehicles using CSMA/CA can experience unacceptable channel access delays and, therefore, 802.11p does not support real-time communications. In addition, we present a potential remedy for this problem, namely, the use of self-organizing time division multiple access (STDMA). The real-time properties of STDMA are investigated by means of the same highway simulation scenario, with promising results.

  • 11.
    Bilstrup, Katrin
    et al.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Ström, Erik G.
    Chalmers, Gothenburg.
    Bilstrup, Urban
    Högskolan i Halmstad, Inbyggda system (CERES).
    On the ability of the IEEE 802.11p and STDMA to provide predictable channel access2009In: Proceedings of the 16th World Congress on Intelligent Transport Systems (ITS), 2009, p. 10-Conference paper (Refereed)
    Abstract [en]

    Emerging traffic safety applications requiring low delay communications will need vehicle ad-hoc networks. The only communication standard currently supporting this is IEEE 802.11p. However, 802.11p uses the medium access method CSMA/CA, which has a major drawback: unbounded worst case channel access delay. We therefore propose an algorithm already in commercial use in the shipping industry: STDMA. With STDMA, nodes always get predictable channel access regardless of the number of competing nodes and the maximum delay is deterministic. In this paper we elaborated with different parameter settings for the two protocols with the aim of improving performance without altering the standards.

     

  • 12.
    Böhm, Annette
    et al.
    Högskolan i Halmstad, Centrum för forskning om inbyggda system (CERES).
    Jonsson, Magnus
    Högskolan i Halmstad, Centrum för forskning om inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Centrum för forskning om inbyggda system (CERES).
    Adaptive Cooperative Awareness Messaging for Enhanced Overtaking Assistance on Rural Roads2011In: IEEE Vehicular Technology Conference (VTC Fall 2011), Piscataway, N.J.: IEEE Press , 2011, p. Article number 609316211-Conference paper (Refereed)
    Abstract [en]

    Cooperative traffic safety applications such as lane change or overtaking assistance have the potential to reduce the number of road fatalities. Many emerging traffic safety applications are based on IEEE 802.11p and periodic position messages, so-called cooperative awareness messages (CAM) being broadcasted by all vehicles. In Europe, ETSI defines a periodic report rate of 2 Hz for CAMs. Although a high report rate is the key to early hazard detection, the 2 Hz rate has been chosen to avoid congestion in settings where the vehicle density is high, e.g., on major highways and in urban scenarios. However, on rural roads with a limited number of communicating vehicles, a report rate of 2 Hz leads to unnecessary delay in cooperative awareness. By adapting the CAM report rate depending on the specific application and road traffic density, and by making use of the priority levels provided by the 802.11p quality of service mechanism, we show that hazards can be detected earlier and the available bandwidth is used more efficiently, while not overexploiting the network resources.

  • 13.
    Dao, Van-Lan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Tran, Hung Vinh
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Reliability and Fairness for CANT Communication Based on Non-Orthogonal Multiple Access2019In: 2019 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS WORKSHOPS (ICC WORKSHOPS), IEEE , 2019Conference paper (Refereed)
    Abstract [en]

    Recently, communication using unmanned aerial vehicles (LAVO as relay nodes has been considered beneficial for a number of applications. Moreover, nomorthogonM multiple access (NONIA) with users being assigned different signal passer levels while sharing the same tune-frequency domain has been found effective to enhance spectrum utilization and provide predictable access to the channel. Thus, in this paper we consider an UAV communication system with NOMA and propose a solution to find the optimal values for the user's power allocation coefficients (PA(s) needed to achieve the required levels of communication reliability. We present a closed-form expression for the PAC of each user and also propose an algori for finding the optimal altitude of the UAV required to satisfy the fairness condition for all users. Finally, we provide numerical mutinies and compare the results tar three types of communication environments.

  • 14.
    Dao, Van-Lan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Tran, Hung Vinh
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Reliability and Fairness for UAV Communication Based on Non-Orthogonal Multiple Access2019In: 2019 IEEE International Conference on Communications Workshops (ICC Workshops), 2019, no 53Conference paper (Refereed)
    Abstract [en]

    Recently, communication using unmanned aerial vehicles (UAVs) as relay nodes has been considered beneficial for a number of applications. Moreover, non-orthogonal multiple access (NOMA) with users being assigned different signal power levels while sharing the same time-frequency domain has been found effective to enhance spectrum utilization and provide predictable access to the channel. Thus, in this paper we consider an UAV communication system with NOMA and propose a solution to find the optimal values for the user’s power allocation coefficients (PACs) needed to achieve the required levels of communication reliability. We present a closed-form expression for the PAC of each user and also propose an algorithm for finding the optimal altitude of the UAV required to satisfy the fairness condition for all users. Finally, we provide numerical examples and compare the results for three types of communication environments.

  • 15.
    Fernandez, Z.
    et al.
    Information and Communication Technologies Area, Ikerlan Technology Research Centre, Mondragón, Spain.
    Val, I.
    Information and Communication Technologies Area, Ikerlan Technology Research Centre, Mondragón, Spain.
    Mendicute, M.
    Signal Theory and Communications Area, Mondragon University, Mondragón, Spain.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Analysis and Evaluation of Self-Organizing TDMA for Industrial Applications2019In: IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS, Institute of Electrical and Electronics Engineers Inc. , 2019Conference paper (Refereed)
    Abstract [en]

    With the Industry 4.0 revolution, the inclusion of wireless communications with real-time requirements has been gaining popularity in industrial applications. As existing wireless technologies do not fully satisfy the stringent requirements of the most critical industrial applications, wired, centralized networks are often used. However, when the application requires mobility, there is no other way than to use wireless communications. Further, in applications where the topology changes dynamically and a large number of devices are mobile, centralized protocols are less suitable. Unfortunately, most decentralized medium access protocols are not predictable, and thereby not able to fulfil the real-time requirements. To address these challenges, in this paper Self-Organizing Time Division Multiple Access (STDMA) is analysed to assess its suitability for use in industrial applications. The analysis has been carried out through simulations under a multipath dispersed time-variant industrial channel while subject to a variable Doppler shift. To this end, several metrics such as channel access delay, slot occupation distribution (SOD), packet losses and packet inter-arrival time (PIAT) have been evaluated, using OMNeT++ in combination with the VEINS framework. 

  • 16.
    Girs, Svetlana
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Bergblomma, Marcus
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Halmstad University, Sweden.
    Štimac, Barbara
    University of Zagreb, Zagreb, Croatia .
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Design of Channel Measurement Guidelines for Characterization of Wireless Industrial Environments2013Report (Other academic)
    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. 

  • 17.
    Girs, Svetlana
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Adopting FEC and Packet Combining to Increase the Performance of IWSNs Using Relaying2015In: International Conference on Computing and Network Communications CoCoNet'15, 2015, p. 90-97Conference paper (Refereed)
    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.

  • 18.
    Girs, Svetlana
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Halmstad University.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Increased Reliability of Reduced Delay in Wireless Industrial Networks Using Relaying and Luby Codes2013Conference paper (Refereed)
    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.

  • 19.
    Girs, Svetlana
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Uhlemann, Elisabeth
    Halmstad University.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering.
    The Effects of Relay Behavior and Position in Wireless Industrial Networks2012In: 2012 9th IEEE International Workshop on Factory Communication Systems, May 21-24, 2012 Lemgo, Germany: Proceedings, 2012, p. 183-190Conference paper (Refereed)
    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.

  • 20.
    Girs, Svetlana
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Willig, Andreas
    Univ Canterbury, Canterbury, New Zealand.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Bjoerkman, Mats
    Halmstad Univ, Halmstad, Sweden.
    On the Role of Feedback for Industrial Wireless Networks Using Relaying and Packet Aggregation2014In: 2014 IEEE INTERNATIONAL CONFERENCE ON INDUSTRIAL TECHNOLOGY (ICIT), 2014, p. 743-748Conference paper (Refereed)
    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.

  • 21.
    Girs, Svetlana
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Willig, Andreas
    University of Canterbury, Canterbury, New Zealand.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Halmstad University, Halmstad, Sweden.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    On the Role of Feedback for Industrial Networks Using Relaying and Packet Aggregation2013Report (Other academic)
    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.

  • 22.
    Girs, Svetlana
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Willig, Andreas
    University of Canterbury, UK.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Halmstad University.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Scheduling for source relaying with packet aggregation in industrial wireless networks2016In: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 12, no 5, p. 1855-1864Article in journal (Refereed)
    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.

  • 23.
    Girs, Svetlana
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Willig, Andreas
    University of Canterbury, Canterbury, New Zealand.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Halmstad University, Halmstad, Sweden .
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Scheduling transmissions in industrial networks using source relaying and packet aggregation2015In: 11th IEEE World Conference on Factory Communication Systems WFCS'15, 2015Conference paper (Refereed)
    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.

  • 24.
    Gutiérrez Peón, Pablo
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. TTTech Computertechnik AG, Vienna, Austria.
    Rodríguez, Pedro Manuel
    IK4-IKERLAN, Arrasate-Mondragón, Spain.
    Fernández, Zaloa
    IK4-IKERLAN, Arrasate-Mondragón, Spain.
    Pozo Pérez, Francisco Manuel
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Val, Iñaki
    IK4-IKERLAN, Arrasate-Mondragón, Spain.
    Steiner, Wilfried
    TTTech Computertechnik AG, Austria.
    Cognitive Radio for Improved Reliability in a Real-Time Wireless MAC Protocol based on TDMA2017In: International Conference on Emerging Technologies And Factory Automation ETFA'17, 2017Conference paper (Refereed)
    Abstract [en]

    Wireless communications enables introduction of Internet of Things (IoT) in industrial networks. Unfortunately, real-time guarantees required for many IoT applications, may be compromised in wireless networks due to an unreliable transmission medium. A key component in enabling real-time communications is the medium access control (MAC) layer and its ability to effectively avoid concurrent transmissions that causes deadline misses. Also, deploying the network in a harsh interference environment can lead to low reliability. Time diversity, based on transmitting several copies of the same data at different instants, increases reliability but at the expense of increased jitter and bandwidth. A more efficient resource utilization is expected from cognitive radio, which dynamically takes into account the status of the wireless environment before performing transmissions. This paper proposes a wireless MAC protocol based on scheduled timeslots to avoid concurrent transmissions, combined with two different mechanisms to increase reliability, one based on time diversity and another on cognitive radio. The protocol and its mechanisms to enhance reliability are compared in different interference scenarios, and show that cognitive radios achieves better performance than time diversity, especially when the interference is produced by a jammer.

  • 25.
    Gutiérrez Peón, Pablo
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. TTTech Computertechnik AG, Vienna, Austria.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Steiner, Wilfried
    TTTech Computertechnik AG, Vienna, Austria.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    A Wireless MAC Method with Support for Heterogeneous Data Traffic2015In: IECON 2015 - 41st Annual Conference of the IEEE Industrial Electronics Society, 2015, p. 3869-3874, article id 7392703Conference paper (Refereed)
    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.

  • 26.
    Gutiérrez Peón, Pablo
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. TTTech Computertechnik AG, Vienna, Austria.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Steiner, Wilfried
    TTTech Computertechnik AG, Vienna, Austria.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Applying Time Diversity for Improved Reliability in a Real-Time Heterogeneous MAC Protocol2017In: 2017 IEEE 85TH VEHICULAR TECHNOLOGY CONFERENCE (VTC SPRING), 2017, article id 8108663Conference paper (Refereed)
    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.

  • 27.
    Gutiérrez Peón, Pablo
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Steiner, Wilfried
    TTTech Computertechnik AG, Austria.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Applying Time Diversity for Improved Reliability in a Real-Time Wireless MAC Protocol2016Report (Other academic)
    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.

  • 28.
    Gutiérrez Peón, Pablo
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Steiner, Wilfried
    TTTech Computertechnik AG.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Medium Access Control for Wireless Networks with Diverse Time and Safety Real-Time Requirements2016In: 42nd Annual Conference of the IEEE Industrial Electronics Society IECON 2016, 2016, p. 4665-4670, article id 7794095Conference paper (Refereed)
    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.

  • 29.
    Hasan, Shahriar
    et al.
    Mälardalen University.
    Balador, Ali
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Towards emergency braking as a fail-safe state in platooning: A simulative approach2019In: IEEE Vehicular Technology Conference, Institute of Electrical and Electronics Engineers Inc. , 2019Conference paper (Refereed)
    Abstract [en]

    Platooning is anticipated to facilitate automated driving even with semi-automated vehicles, by forming road trains using breadcrumb tracing and Cooperative Adaptive Cruise Control (CACC). With CACC, the vehicles coordinate and adapt their speed based on wireless communications. To keep the platoon fuel-efficient, the inter-vehicle distances need to be quite short, which requires automated emergency braking capabilities. In this paper, we propose synchronized braking, which can be used together with existing CACC controllers. In synchronized braking, the leading vehicle in the platoon does not brake immediately, but instead communicates its intentions and then, slightly later, the whole platoon brakes simultaneously. We show that synchronized braking can avoid rear-end collisions even at a very high deceleration rate and with short inter- vehicle distances. Also, the extra distance travelled during the delay before braking can be compensated by enabling a higher deceleration, through coordinated synchronized braking.

  • 30.
    Hoang, L. -N
    et al.
    Halmstad University, Halmstad, Sweden.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Halmstad University, Halmstad, Sweden.
    Jonsson, M.
    Halmstad University, Halmstad, Sweden.
    A framework for reliable exchange of periodic and event-driven messages in platoons2015In: 2015 IEEE International Conference on Communication Workshop, ICCW 2015, 2015, p. 2471-2476Conference paper (Refereed)
    Abstract [en]

    Platooning is widely considered a promising approach to decrease fuel consumption by reducing the air drag. However, in order to achieve the benefits of aerodynamic efficiency, the inter-vehicle distances must be kept short. This implies that the intra-platoon communication must not only be reliable but also able to meet strict timing deadlines. In this paper, we propose a framework that reliably handles the co-existence of both time-triggered and event-driven control messages in platooning applications and we derive an efficient message dissemination technique. We propose a semi-centralized time division multiple access (TDMA) approach, which e.g., can be placed on top of the current standard IEEE 802.11p and we evaluate the resulting error probability and delay, when using it to broadcast periodic beacons and disseminating event-driven messages within a platoon. Simulation results indicate that the proposed dissemination policy significantly enhances the reliability for a given number of available time-slots, or alternatively, reduces the delay, in terms of time-slots, required to achieve a certain target error probability, without degrading the performance of co-existing time-triggered messages.

  • 31.
    Hoang, L. -N
    et al.
    Halmstad University, Halmstad, Sweden.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Halmstad University, Halmstad, Sweden.
    Jonsson, M.
    Halmstad University, Halmstad, Sweden.
    An efficient message dissemination technique in platooning applications2015In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, no 6, p. 1017-1020, article id 7066951Article in journal (Refereed)
    Abstract [en]

    Autonomous driving in road trains, a.k.a. platooning, may reduce fuel consumption considerably if the inter-vehicle distances are kept short. However, to do this, the intra-platoon communication must not only be reliable but also able to meet strict deadlines. While time-triggered messages are the foundation of most distributed control applications, platooning is likely to also require dissemination of event-driven messages. While much research work has focused on minimizing the age of periodic messages, state-of-the-art for disseminating event-driven messages is to let all nodes repeat all messages and focus on mitigating broadcast storms. We derive an efficient message dissemination scheme based on relay selection which minimizes the probability of error at the intended receiver(s) for both unicast and broadcast, without degrading the performance of co-existing time-triggered messages. We present a full analysis of the resulting error probability and delay, when relayers, selected by our algorithm, are used to disseminate messages within a platoon. Numerical results indicate that the proposed relaying policy significantly enhances the reliability for a given delay.

  • 32.
    Hoang, L. -N
    et al.
    Halmstad University, Halmstad, Sweden.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Halmstad University, Halmstad, Sweden.
    Jonsson, M.
    Halmstad University, Halmstad, Sweden.
    Low Complexity Algorithm for Efficient Relay Assignment in Unicast/Broadcast Wireless Networks2017In: IEEE Vehicular Technology Conference (VTC) Proceedings, ISSN 1550-2252, Vol. June, article id 8108261Article in journal (Refereed)
    Abstract [en]

    Using relayers in wireless networks enables higher throughput, increased reliability or reduced delay. However, when building networks using commercially available hardware, concurrent transmissions by multiple relayers are generally not possible. Instead one specific relayer needs to be assigned for each transmission instant. If the decision regarding which relayer to assign, i.e., which relayer that has the best opportunity to successfully deliver the packet, can be taken online, just before the transmission is to take place, much can be gained. This is particularly the case in mobile networks, as a frequently changing network topology considerably affects the choice of a suitable relayer. To this end, this paper addresses the problem of online relay assignment by developing a low-complexity algorithm highly likely to find the optimal combination of relaying nodes that minimizes the resulting error probability at the targeted receiver(s) using a mix of simulated annealing and ant colony algorithms, such that relay assignments can be made online also in large networks. The algorithm differs from existing works in that it considers both unicast as well as broadcast and assumes that all nodes can overhear each other, as opposed to separating source nodes, relay nodes and destination nodes into three disjoint sets, which is generally not the case in most wireless networks. 

  • 33.
    Hoang, L. -N
    et al.
    CERES, Halmstad University, Halmstad, Sweden.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. CERES, Halmstad University, Halmstad, Sweden.
    Jonsson, Magnus
    CERES, Halmstad University, Halmstad, Sweden.
    A novel relaying scheme to guarantee timeliness and reliability in wireless networks2016In: 2016 IEEE Globecom Workshops, GC Wkshps 2016 - Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2016Conference paper (Refereed)
    Abstract [en]

    Many emerging applications based on wireless networks involve distributed control. This implies high requirements on reliability, but also on a predictable maximum delay and sometimes jitter. Further, many distributed control systems need to be constructed using off-the-shelf components, both due to cost constraints and due to interoperability with existing networks. This, in turn, implies that concurrent transmissions and multiuser detection are seldom possible. Instead, half-duplex time division multiple access (TDMA) is typically used. The total communication delay thereby depends on the packet error rate and the time until channel access is granted. With TDMA, channel access is upper-bounded and the jitter can be set to zero. With the aim to reduce the packet error rate given a certain deadline (a set of TDMA time-slots), we propose a novel relaying scheme, which can be implemented on top of off-the-shelf components. The paper includes a full analysis of the resulting error probability and latency. Numerical results show that the proposed relaying strategy significantly improves reliability given a certain maximum latency, or alternatively, reduces the latency, given a certain target reliability requirement.

  • 34.
    Hoang, Le-Nam
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Jonsson, M.
    School of Information Technology, Halmstad University, Halmstad, Sweden.
    Relay Grouping to Guarantee Timeliness and Reliability in Wireless Networks2019In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 23, no 9, p. 1661-1664, article id 8737952Article in journal (Refereed)
    Abstract [en]

    Relaying can increase reliability, range, or throughput. In many cyber-physical systems (CPS), relaying is used to maximize reliability before a given deadline. Since concurrent transmissions are not supported by most CPS, time-division multiple access (TDMA) is typically used. However, a major drawback of relaying in TDMA is that pre-allocated time-slots are wasted if their respective transmitters do not have any correctly received packet to relay. Therefore, in this letter, we propose a novel relay grouping scheme to overcome this drawback. Numerical results show that the proposed scheme significantly enhances the reliability while guaranteeing the deadline for each message. 

  • 35.
    Hoang, Le-Nam
    et al.
    Halmstad Univ, CERES, Halmstad, Sweden..
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Halmstad Univ, CERES, Halmstad, Sweden.
    Jonsson, Magnus
    Halmstad Univ, CERES, Halmstad, Sweden..
    Relaying with Packet Aggregation for Half-Duplex All-to-All Broadcast in Time-Critical Wireless Networks2017In: 2017 IEEE GLOBECOM WORKSHOPS (GC WKSHPS), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    Wireless automation and control networks, with stringent latency and reliability requirements, typically use halfduplex communications combined with deadline-aware scheduling of time slots to nodes. To introduce higher reliability in legacy industrial control systems, extra time slots are usually reserved for retransmissions. However, in distributed wireless control systems, where sensor data from several different nodes must be timely and reliably available at all places where controller decisions are made, this is particularly cumbersome as all nodes may not hear each other and extra time slots imply increased delay. To enable all-to-all broadcast with manageable overhead and complexity in such systems, we therefore propose a novel relaying strategy using packet aggregation. The strategy assigns relayers to time slots, as well as determines which packets to aggregate in each slot, using a low-complexity algorithm such that ultra-reliable communications can be obtained with maintained end-to-end latency.

  • 36.
    Ku, Bih-Yuan
    et al.
    National Taipei University of Technology, Taiwan .
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Report on Rail Conference and Wireless Communications: [VTS News]2011In: IEEE Vehicular Technology Magazine, ISSN 1556-6072, E-ISSN 1556-6080, Vol. 6, no 3, p. 111-117Article in journal (Other academic)
    Abstract [en]

    The 2011 Joint Rail Conference (JRC) was held in Pueblo, Colorado, on March 16-18, 2011, immediately after the Association of American Railroads Research Review. The conference started with a technical tour of TTCi. The highlights of the technical tour were two on-site presentations on a full-scale train impact test and the field test of the positive train control (PTC) system. The tour attendees were given the opportunity to take a close look at the energy-absorption devices and sensors installed at various locations of the test car. The PTC presentation was held at the communications and train control (C&TC) test bed at the TTCi test track, which is the only CT&C test bed in North America. The 2012 Joint Rail Conference (JRC) will be held in Philadelphia in April 2012, and the IEEE Vehicular Technology Society (VTS) Land Transportation Division (LTD) will take the lead in the planning of the major technical forum onrail engineering in North America.

  • 37.
    Kunert, Kristina
    et al.
    Högskolan i Halmstad, Centrum för forskning om inbyggda system (CERES).
    Jonsson, Magnus
    Högskolan i Halmstad, Centrum för forskning om inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Centrum för forskning om inbyggda system (CERES).
    Exploiting time and frequency diversity in IEEE 802.15.4 industrial networks for enhanced reliability and throughput2010In: 2010 IEEE Conference on Emerging Technologies and Factory Automation (ETFA), 2010, p. Article number 5641347-Conference paper (Refereed)
    Abstract [en]

    Industrial networks based on IEEE 802.15.4 are spreading, even though the joint requirement on predictability and reliability from industrial applications is hard to fulfil in wireless networks, and the data rate of IEEE 802.15.4 is rather low. With the goal of providing real-time guarantees, with increased reliability and throughput, we propose two multichannel network architectures based on IEEE 802.15.4 with predictable medium access, real-time analysis admission control and transport layer retransmissions. We evaluate the architectures in terms of reliability, utilization, delay, complexity, scalability and energy efficiency. The evaluations show that throughput and reliability can be enhanced through redundancy and concurrency in the frequency domain.

  • 38.
    Kunert, Kristina
    et al.
    Högskolan i Halmstad, Centrum för forskning om inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Centrum för forskning om inbyggda system (CERES).
    Jonsson, Magnus
    Högskolan i Halmstad, Centrum för forskning om inbyggda system (CERES).
    Enhancing reliability in IEEE 802.11 based real-time networks through transport layer retransmissions2010In: 2010 International Symposium on Industrial Embedded Systems (SIES), 2010, p. 146-155Conference paper (Refereed)
    Abstract [en]

    As the number of application areas for wireless technologies grows, the need for providing both predictable and reliable communication over wireless networks becomes apparent. Cooperative embedded systems for industrial automation are one example of systems with these needs. Previously, we developed a framework for reliable real-time communication in a single-hop wireless network with a logical star topology. The framework was placed on top of IEEE 802.15.4 and combines transport layer retransmissions with real-time analysis admission control. IEEE 802.15.4 was selected due to its advantageous energy saving techniques, making it an interesting choice for wireless sensor networks in industrial contexts. However, its achievable data rate is rather low, especially when voice or video for industrial surveillance and monitoring need to be transferred. Hence, we adapt our framework to fit the IEEE 802.11 standard and evaluate its performance using a data traffic model from industrial control and surveillance systems. The performance of the framework is evaluated in terms of network utilization, message error rate and delay distribution using theoretical analysis as well as computer simulations.

     

  • 39.
    Kunert, Kristina
    et al.
    Högskolan i Halmstad, Centrum för forskning om inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Centrum för forskning om inbyggda system (CERES).
    Jonsson, Magnus
    Högskolan i Halmstad, Centrum för forskning om inbyggda system (CERES).
    Predictable real-time communications with improved reliability for IEEE 802.15.4 based industrial networks2010In: 2010 8th IEEE International Workshop on Factory Communication Systems (WFCS), 2010, p. 13-22Conference paper (Refereed)
    Abstract [en]

    Emerging industrial applications requiring reliable wireless real-time communications are numerous. Using existing standards such as IEEE 802.15.4 is essential for reasons of interoperability and cost efficiency. However, since 802.15.4 is unable to provide predictable channel access, real-time guarantees cannot be given. Further, the noisy wireless channel makes reliable communications particularly challenging. By adding a deterministic medium access method and a transport protocol with a truncated retransmission scheme to 802.15.4, we jointly enforce reliability and predictability. We evaluate our solution analytically by real-time schedulability analysis including retransmissions, and by computer simulations. We show that the message error rate can be improved by several orders of magnitude while keeping the utilization penalty at reasonable levels.

  • 40.
    Lisova, Elena
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Causevic, Aida
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Clock Synchronization Considerations in Security Informed Safety Assurance of Autonomous Systems of Systems2017In: IECON 2017 - 43RD ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY, 2017, p. 8385-8390Conference paper (Refereed)
  • 41.
    Lisova, Elena
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Gutiérrez, Marina
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Steiner, Wilfried
    TTTech Computertechnik AG, Austria.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Åkerberg, Johan
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Dobrin, Radu
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Protecting Clock Synchronization: Adversary Detection through Network Monitoring2016In: Journal of Electrical and Computer Engineering, ISSN 2090-0147, E-ISSN 2090-0155, article id 6297476Article in journal (Refereed)
    Abstract [en]

    Today, industrial networks are often used for safetycritical applications with real-time requirements. The architecture of such applications usually has a time-triggered nature that has message scheduling as a core property. Real-time scheduling can be applied only in networks where nodes share the same notion of time, i.e., they are synchronized. Therefore, clock synchronization is one of the fundamental assets of industrial networks with real-time requirements. However, standards for clock synchronization, i.e., IEEE 1588, do not provide the required level of security. This raises the question about clock synchronization protection. In this paper we identify a way to break synchronization based on the IEEE 1588 standard by conducting a man-in-the-middle (MIM) attack followed by a delay attack. MIM attack can be accomplished through e.g., Address Resolution Protocol (ARP) poisoning. Using AVISPA tool we evaluate the potential to perform an ARP poisoning attack. Next, an analysis of the consequences of introducing delays is made, showing both that the attack can, indeed, break clock synchronization and that some design choices, such as a relaxed synchronization condition mode, delay bounding and using knowledge of environmental conditions, can be made to make the network more robust/resilient against these kinds of attacks. Lastly, network monitoring is proposed as a technique to detect anomalies introduced by an adversary performing attacks targeting clock synchronization. The monitoring capabilities are added to the network using a Configuration Agent, which, based on data obtained from the network, is able to detect an attack. The main contribution of the paper is a detailed problem description and evaluation of a security vulnerability in IEEE 1588 against delay attacks together with an evaluation of several approaches as possible mitigation techniques for the attack.

  • 42.
    Lisova, Elena
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Steiner, W.
    TTech Computertecnik AG, Vienna, Austria.
    Åkerberg, Johan
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Game theory applied to secure clock synchronization with IEEE 15882016In: IEEE International Symposium on Precision Clock Synchronization for Measurement, Control, and Communication, ISPCS, 2016Conference paper (Refereed)
    Abstract [en]

    Industrial applications usually have real-time requirements or high precision timing demands. For such applications, clock synchronization is one of the main assets that needs to be protected against malicious attacks. To provide sufficient accuracy for distributed time-critical applications, appropriate techniques for preventing or mitigating delay attacks that breach clock synchronization are needed. In this paper, we apply game theory to investigate possible strategies of an adversary, performing attacks targeting clock synchronization on the one hand and a network monitor, aiming to detect anomalies introduced by the adversary on the other. We investigate the interconnection of payoffs for both sides and propose the quarantine mode as a mitigation technique. Delay attacks with constant, linearly increasing, and randomly introduced delays are considered, and we show how the adversary strategy can be estimated by evaluating the detection coefficient, giving the network monitor the possibility to deploy appropriate protection techniques.

  • 43.
    Lisova, Elena
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Steiner, Wilfried
    TTTech Computertechnik AG, Austria.
    Åkerberg, Johan
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    A Survey of Security Frameworks Suitable for Distributed Control Systems2015In: International Conference on Computing and Network Communications CoCoNet'15, 2015, p. 205-211Conference paper (Refereed)
    Abstract [en]

    Nowadays distributed control systems have become more and more common and important in everyday life. However, as many distributed control systems become mobile, wireless, autonomous, ubiquitous and connected, the need for secure communication is imminent. In particular, the need for a general security framework with sufficiently flexible structure, and applicable for various use cases, emerges. Especially this applies to control system based on heterogeneous networks consisting of a wired and a wireless parts. Wired networks are nowadays often connected to Internet and thereby more exposed to potential attackers, and wireless networks are, by nature, more vulnerable to eavesdropping, jamming and hijacking. In this paper we define a scope of use cases based on distributed control, together with requirements for evaluating existing security solutions and frameworks. In addition, several frameworks, mainly from the area of industrial automation, are surveyed and evaluated based on the identified use cases and security requirements.

  • 44.
    Lisova, Elena
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Steiner, Wilfried
    TTTech Computertechnik AG, Austria.
    Åkerberg, Johan
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Risk Evaluation of an ARP Poisoning Attack on Clock Synchronization for Industrial Applications2016In: Proceedings of the IEEE International Conference on Industrial Technology, 2016, Vol. may, p. 872-878, article id 7474866Conference paper (Refereed)
    Abstract [en]

    Nowadays, mixed wireless and wired networks are used everywhere in everyday life, including in industry where they often support time-critical applications. Industrial applications with high precision requirements are subject to real-time constraints, and thus one of the main assets, regardless of application area, is clock synchronization. Considering such networks, synchronization is the first thing to secure against a possible malicious adversary. In this paper, we consider ARP poisoning as a possible technique to disrupt clock synchronization and evaluate the effects of such an attack on the IEEE 1588 standard. We describe possible ways of performing ARP poisoning to disrupt synchronization and survey several mitigation techniques and their applicability within the industrial application area.

  • 45.
    Lisova, Elena
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Åkerberg, Johan
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Monitoring of Clock Synchronization in Cyber-Physical Systems: A Sensitivity Analysis2017In: International Conference on Internet of Things, Embedded Systems and Communications 2017 IINTEC 2017, 2017, p. 134-139Conference paper (Refereed)
    Abstract [en]

    Clock synchronization is a core asset to protect when securing cyber-physical systems with a time-triggered architecture. One of the most challenging attacks to protect against is a delay attack, where an adversary delays one of the synchronization messages, making node offset calculations incorrect for keeping clocks synchronized. One way to detect a breach of clock synchronization is by monitoring the offsets calculated in a node according to the clock synchronization algorithm. The analysis in this work assumes that the distributed nodes need to share the same notion of time and for this reason, uses the IEEE 1588 standard. Using this approach, a monitor needs to make a decision about if and when a node is under attack, in which case rules and methods for decision making should be put in place. There are many aspects to consider when setting thresholds for the monitored values in order to make such a decision. In this work we conduct an analysis of monitor indicators and an investigation of their applicability. Further, we identify dependencies within the proposed monitoring approach and conduct a sensitivity analysis of the parameters needed to make a decision about a system being under attack. The analysis outcomes allow to identify important parameters to consider while thresholding indicators and enables a greater generality in their applicability.

  • 46.
    Lisova, Elena
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Åkerberg, Johan
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Mats, Björkman
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Delay attack versus clock synchronization - A time chase2017In: Proceedings of the IEEE International Conference on Industrial Technology, 2017, p. 1136-1141Conference paper (Refereed)
    Abstract [en]

    Clock synchronization is one of the most essential assets for distributed real-time systems, as sensing, control and actuation require synchronized communication to meet real-time deadlines. We propose a distributed monitoring method to detect if an adversary is interfering with the clock synchronization protocol. The monitor uses certain network indicators and a set of rules to decide about switching between Normal, Quarantine or Attack Detected states. Further, we propose a way to define thresholds for decision-making based on theoretical analysis of the indicator values influenced by an attack. In addition, we formulate the problem of adversary influence detection in the network as a detection theory problem and use it to derive an additional indicator for the network monitor. Finally, we analyze the time chase between the monitor and an adversary to investigate which factors influence the final outcome. 

  • 47.
    Lisova, Elena
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Åkerberg, Johan
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Steiner, Wilfried
    TTTech Computertechnik AG, Austria.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Game Theory Applied to Secure Clock Synchronization with IEEE 15882016Report (Other academic)
  • 48.
    Mecklenbräuker, Christoph
    et al.
    Vienna University of Technology, Vienna, Austria.
    Bernadó, Laura
    FTW Forschungszentrum Telekommunikation Wien, Vienna, Austria.
    Klemp, Oliver
    BMW Forschung und Technik, Munich, Germany.
    Kwoczek, Andreas
    Volkswagen AG, Wolsburg, Germany.
    Paier, Alexander
    Vienna University of Technology, Vienna, Austria.
    Schack, Moritz
    Technische Universität Braunschweig, Braunschweig, Germany.
    Sjöberg, Katrin
    Högskolan i Halmstad, Inbyggda system (CERES).
    Ström, Erik
    Chalmers University of Technology, Gothenburg, Sweden.
    Tufvesson, Fredrik
    Lund University, Lund, Sweden.
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Zemen, Thomas
    FTW Forschungszentrum Telekommunikation Wien, Vienna, Austria.
    Vehicle-to-Vehicle Communications2012In: Pervasive Mobile and Ambient Wireless Communications: Cost Action 2100 / [ed] Roberto Verdone & Alberto Zanella, London: Springer London , 2012, p. 577-608Chapter in book (Other academic)
    Abstract [en]

    This chapter discusses major results and conclusions from Special Interest Group C bringing together various aspects of mobile to mobile communication from all working groups. Vehicle-to-vehicle communication scenarios are emphasized. Traffic telematics applications are currently under intense research and development for making transportation safer, more efficient, and cleaner. Communication systems which provide “always on” connectivity at data rates between 1 and 10 Mb/s to highly mobile surface traffic (cars and trains) are urgently required for developing traffic telematics applications and services. Currently much attention is given to advanced active safety, but the application area also ranges to improved navigation mechanisms and infotainment services. mobile to mobile communications need to be reliable and trusted: Drivers in cars which are equipped with vehicle to vehicle communications need to rely on the accuracy and timeliness of the exchanged data. Automotive manufacturers, road authorities, broadcast companies, and telecom providers are the key players in the value chain for such future systems. These communication systems provide an extended information horizon to warn the driver or the vehicular systems of potentially dangerous situations in an early phase.

  • 49.
    Morsi Mahmod, Mohamed
    et al.
    University of Twente, Sweden.
    Khalil, Issam
    Ericsson AB, Branch Office Sudan, Sudan.
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Sweden.
    Nygren, Niclas
    Volvo Technology Corporation, Transport, Information and Communication, Sweden.
    Wireless strategies for future and emerging ITS applications2008In: 15th World Congress on Intelligent Transport Systems: New York, USA, November 16-20, 2008 : ITS connections, saving time, saving lives, New York: World Congress on Intelligent Transport Systems (ITS) , 2008, p. 12-Conference paper (Refereed)
    Abstract [en]

    Within the Intelligent Transportation Systems (ITS) field, many applications of a diverse nature are considered and thus their communication requirements differ significantly. This makes it difficult for one wireless carrier to support all or most of these applications. Therefore, we have complied a list of communication requirements for future ITS applications and used it to analyze different ITS applications as well as different wireless carriers. Accordingly, the applications can be grouped into different requirements profiles with recommended wireless carriers assigned to each profile. The concept of profiling can also be used to classify the applications according to their non-technical requirements and hence accelerate their future deployment by encouraging involved stakeholders to make the most common requirements available. It can also be useful when developing a roadmap for deployment of future ITS applications defining which application will most likely be implemented first.

  • 50.
    Quach, T. X.
    et al.
    VNU University Engineering and Technology, Vietnam.
    Tran, Hung Vinh
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Truc, M. T.
    VNU University Engineering and Technology, Vietnam.
    Secrecy performance of cognitive cooperative industrial radio networks2017In: IEEE Conference on Emerging Technologies and Factory Automation, ISSN 1946-0740, E-ISSN 1946-0759, Vol. Part F134116, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Although cognitive radio networks (CRNs) were originally intended as a powerful solution to enhance spectrum utilization, it can also be used to improve reliability by avoiding interference in the 2.4 or 5 GHz band. Using multiple relay nodes in CRNs, the outage probability, i.e., the probability that the end-to-end signal-to-noise ratio drops below a predefined threshold, can be reduced significantly. This implies that the probability that a message is not delivered within a specific time frame, can be kept below a required threshold, even when there are constraints on energy efficiency in terms of peak transmit power. This is particularly useful for industrial networks with realtime constraints. However, using CRNs may also reveal secret information to eavesdroppers (EAVs). Therefore, guaranteeing secure and reliable communications in CRNs is still a challenging problem. To this end, the secrecy performance of a proactive decode-and-forward relaying scheme in a cognitive cooperative radio network is investigated. More specifically, analytical as well as approximate expressions for the secrecy outage probability and probability of non-zero secrecy capacity are derived to evaluate the system performance. Numerical results show that the approximation tightly match the analytical results and simulations, and thus it can be used to provide a fast evaluation of the security and reliability of communications using a considered assignment of relay nodes in a cognitive cooperative radio network (CCRN). Consequently, our results enable to secure the communication, and increasing the reliability, availability, robustness, and maintainability of wireless industrial network, subject to various constraints from the CRN. 

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