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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.
    Ashjaei, Seyed Mohammad Hossein
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Dynamic Resource Distribution using SDN in Wireless Networks2020In: 21st IEEE International Conference on Industrial Technology ICIT'20, 2020, p. 967-972Conference paper (Refereed)
  • 3.
    Dao, Van-Lan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Innovation and Product Realisation.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Dealing with Jamming Attacks in Uplink Pairwise NOMA Using Outage Analysis, Smart Relaying and Redundant Transmissions2024In: Open Journal of the Communications Society, Vol. 5, p. 112-126Article in journal (Refereed)
    Abstract [en]

    This study focuses on optimizing the performance of an uplink pairwise Non-Orthogonal Multiple Access (NOMA) scenario with and without the support of a relayer, while subject to jamming attacks. We consider two different relaying protocols, one where the sources and the destination are within range of each other and one where they are not. The relay node can be mobile, e.g., a mobile base station, an unmanned aerial vehicle (UAV) or a stationary node that is chosen as a result of a relay selection procedure. We also benchmark with a NOMA retransmission protocol and an Orthogonal Multiple Access (OMA) scheme without a relayer. We analyze, adjust and compare the four protocols for different settings using outage analysis, which is an efficient tool for establishing communication reliability for both individual nodes and the overall wireless network. Closed-form expressions of outage probabilities can be adopted by deep reinforcement learning (RL) algorithms to optimize wireless networks online. Accordingly, we first derive closed-form expressions for the individual outage probability (IOP) of each source node link and the relayer link using both pairwise NOMA and OMA. Next, we analyze the IOP for one packet (IOPP) for each source node considering all possible links between the source node to the destination, taking both phases into account for the considered protocols when operating in Nakagami-m fading channels. The overall outage probability for all packets (OOPP) is defined as the maximum IOPP obtained among the source nodes. This metric is useful to optimize the whole wireless network, e.g., to ensure fairness among the source nodes. Then, we propose a method using deep RL where the OOPP is used as a reward function in order to adapt to the dynamic environment associated with jamming attacks. Finally, we discuss valuable guidelines for enhancing the communication reliability of the legitimate system.

  • 4.
    Dao, Van-Lan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Innovation and Product Realisation.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Defeating Jamming Attacks in Downlink Pairwise NOMA Using Relaying2023Conference paper (Refereed)
    Abstract [en]

    This study explores an incremental relaying strategy in downlink pairwise Non-Orthogonal Multiple Access (NOMA), which involves multiple pairs of nodes near and far from the downlink destinations. The strategy aims to select a near destination node to relay the packet of a far destination node, considering the presence of jamming attacks. To this end, we first derive closed-form expressions for the individual outage probability (IOP) for both near and far destinations in Nakagami-m fading channels. Next, the overall IOP (OIOP) performance is defined as the maximum value among the obtained IOPs, ensuring fairness among the nodes. To optimize the system, simulated annealing algorithms are proposed to determine the best power allocation and the best relay-destination pairing. We can conclude that both the power allocation and the position/selection of the near destination node significantly impact the OIOP for a specific pair. However, in the case of multiple pairs of destinations, a good power allocation alone suffices for each pair, and fixed or even random destination pairing is satisfactory in the considered context.

  • 5.
    Dao, Van-Lan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Innovation and Product Realisation.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Outage Performance Comparison of Adaptive Relaying Schemes Subject to Jamming2023Conference paper (Refereed)
    Abstract [en]

    Proper relay selection (RS) plays a key role for improving the reliability of wireless networks, especially in the presence of jamming attacks and/or interferers. In this work, we consider several RS schemes from the literature, using e.g. channel gains and signal-to-interference plus noise ratio (SINR) to select a relayer and evaluate them using outage probability (OP). We also propose an RS scheme which is selecting relayers to maximize the communication reliability in terms of minimizing the OP. The suggested RS strategy also takes the effect of jamming attacks and/or interferers into account. Accordingly, an intensive investigation of the OP of all RS schemes considering also jammers' positions in various scenarios is conducted. The results suggest that a combination of RS schemes using channel gains and SINRs of all hops achieves the best communication reliability in scenarios with intensive interference. The sensitivity for channel estimation errors of the relaying schemes is also investigated. Finally, discussions about the obtained results together with the complexity of all RS schemes are presented before providing guidelines on which schemes should be used in which scenarios to improve the communication reliability.

  • 6.
    Dao, Van-Lan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hoang, Le-Nam
    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.
    Defeating Jamming Using Outage Performance Aware Joint Power Allocation and Access Point Placement in Uplink Pairwise NOMA2021In: IEEE Open Journal of the Communications Society, E-ISSN 2644-125X, Vol. 2, p. 1957-1979Article in journal (Refereed)
    Abstract [en]

    In this paper, an uplink pairwise Non-Orthogonal Multiple Access (NOMA) scenario using a mobile access point (AP) or an unmanned aerial vehicle in the presence of a jamming attack is considered. To mitigate the influence of the jamming attack, a joint power allocation and AP placement design is proposed. Accordingly, closed-form expressions of the overall outage probability (OOP) and the individual outage probability (TOP) considering imperfect channel state information for each of the source nodes the AP serves, are derived over Nakagami-m fading channels using dynamic decoding order and fixed pairwise power allocation. We conduct an investigation of the effect of different parameters such as power allocation, source node placements, AP placement, target rates, and jammer location on the OOP and the IOP performance. By adapting the power allocation and the AP placement to the jamming attack, the communication reliability can be increased significantly compared to neglecting the presence of the jammer or treating the jammer as noise. Since the malicious jammer and the AP have conflicting interests in terms of communication reliability, we formulate a non-cooperative game for the two players considering their positions and the power allocation of the NOMA nodes as their strategies and the OOP as utility function. We propose using hybrid simulated annealing - greedy algorithms to address the joint power allocation and AP placement problem for the cases of both a fixed and a mobile jammer. Finally, the Nash equilibrium points are obtained and then the UAV goes directly to this position and keeps staying there to save power consumption.

  • 7.
    Dao, Van-Lan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hoang, Le-Nam
    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.
    Outage Performance of Pairwise NOMA Allowing a Dynamic Decoding Order and Optimal Pairs of Power Levels2020In: IEEE Open Journal of the Communications Society, E-ISSN 2644-125X, Vol. 1, p. 1886-1906Article in journal (Refereed)
    Abstract [en]

    In this article, we evaluate the overall outage probability (OOP) of pairwise Non-orthogonal Multiple Access (NOMA) for both uplink and downlink. We also propose a dynamic decoding order (DDO) together with a fixed pairwise power allocation (FPPA) scheme, in which the optimal decoding order is decided based on the instantaneous channel gains, and thereafter, a pair of power levels is assigned in accordance with the selected decoding order. Exact closed-form expressions of the OOPs for both uplink and downlink pairwise NOMA considering all proposed decoding orders over Nakagami- m fading are derived. Further, we find the optimal fixed power levels for different power allocation strategies so that the OOPs are minimized. Moreover, we investigate the influence of the distances between the source nodes and the access point (AP), the target transfer rates and the path-loss exponents on the OOPs for all cases of decoding orders. In addition, we benchmark our proposed DDO against other decoding orders in terms of the OOP. The results show that assigning optimal fixed power levels which takes the instantaneous decoding order into account not only improves the communication reliability, but also reduces the complexity and computational load at the AP.

  • 8.
    Dao, Van-Lan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Tran, Hung
    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.

  • 9.
    Dao, Van-Lan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Tran, Hung
    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.

  • 10.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering.
    Cooperative Communication for Increased Reliability in Industrial Wireless Networks2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Introducing wireless networks into distributed industrial systems may enable new or improved application areas and also great cost reductions due to lower complexity of installation and maintenance, compared to existing wired solutions. However, signals travelling through wireless channels are affected by pathloss, fading and shadowing, and, as a result, packet errors are both time-varying and more frequent than in e.g., existing wired fieldbuses. Packet errors or delays occurring in industrial systems can, in critical situations, lead to damage of expensive equipment or even danger to human life. Thus, wireless networks can be accepted for use in industrial networks only when sufficient levels of reliability and timeliness can be guaranteed.

    Relaying is a technique that has the potential to increase reliability with maintained delay. Having different geographical locations, and thus different wireless channel qualities, some nodes may overhear transmitted packets even in cases when the intended receiver did not, and then cooperate by relaying these packets to their final destination.

    This thesis deals with design of relaying strategies aiming to increase reliability in deadline-constrained industrial applications using wireless networks. The influence of several different parameters, such as positions of relay nodes, number of erroneous packets at the relay node and at the destination respectively, as well as the number of available time slots before the deadline, are evaluated to determine the best acting strategy for each relay node. Moreover, it is shown that when a specific relay node has the opportunity to aid more than one source node, performance can be improved even further if the relay node combines several packets, using Luby coding or packet aggregation, and instead relays such combined packets. Given the methods proposed in this thesis, the reliability in industrial wireless networks can be enhanced considerably, without increasing the delay, such that message deadlines still are kept.

    Download full text (pdf)
    fulltext
  • 11.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Relaying for Industrial Wireless Networks2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The interest in wireless technology for industrial applications has increased dramatically over the last few years. Wireless communication can reduce cost and complexity, enable mobility and provide much higher flexibility than its wired counterparts. However, to be considered for use in practice, wireless systems must provide sufficient levels of timeliness and reliability as required by industrial applications, while keeping reasonable levels of complexity as well as interoperability with existing wired networks. Wireless channels, characterized by pathloss, noise, multipath fading and shadowing, imply a particular challenge to fulfill the requirements on timely and reliable communication. To this end, this thesis work proposes and evaluates a number of techniques able to increase the reliability of wireless communication systems without causing excessive or unpredictable delays. In addition, all proposed solutions are implementable on top of commercially available devices, i.e., they require no large alteration of the standard IEEE 802.15.4 and minimal changes to the current infrastructure to be compatible with existing industrial communication systems. First, the characteristics of industrial communication environments are determined. Then, suitable models to approximate them are selected, since the effectiveness of different error control schemes able to increase reliability depends on the type of wireless channel encountered. Next, different possibilities for reliability improvements in wireless industrial networks, while subject to strict timing constraints, are evaluated. Based on this, relaying that has been proven to be beneficial for traditional wireless networks is evaluated for applicability in industrial systems. Finally, several different relaying strategies that are implementable at the link layer on top of existing chipsets are developed and evaluated. Depending on the specific type of industrial application and its corresponding performance metrics, relaying is combined with network coding, forward error control codes, packet aggregation and packet combining techniques – all of which support increased reliability with maintained delay, at reasonable complexity investments. To complete the framework, scheduling schemes tailored to various relaying protocols are also developed.

  • 12.
    Girs, Svetlana
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Ashjaei, Seyed Mohammad Hossein
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Designing a Bandwidth Management Scheme for Heterogeneous Virtualized Networks2018In: International Conference on Emerging Technologies and Factory Automation - Work in Progress Session ETFA-WiP'18, 2018, p. 1079-1082, article id 8502450Conference paper (Refereed)
    Abstract [en]

    With envisioned increased density and complexity of future industrial networks, software defined networking (SDN) and network virtualization are considered to be promising techniques for network organization and management. Thus, in this paper we look at heterogeneous software defined networks consisting of several virtual slices and present a bandwidth control algorithm, which is designed to provide control over shared bandwidth both in wired and wireless parts of the network. The designed algorithm has been implemented in real hardware and in this paper we present the initial test results.

  • 13.
    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. 

    Download full text (pdf)
    fulltext
  • 14.
    Girs, Svetlana
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Sentilles, Séverine
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Abbaspour Asadollah, Sara
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Ashjaei, Seyed Mohammad Hossein
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Mubeen, Saad
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    A Systematic Literature Study on Definition and Modeling of Service-Level Agreements for Cloud Services in IoT2020In: IEEE Access, E-ISSN 2169-3536, Vol. 8, p. 134498-134513, article id 9146632Article in journal (Refereed)
    Abstract [en]

    The cloud computing paradigm provides remote computing resources to the cloud service consumers and businesses. When combined with Internet of Things (IoT), both technologies open up a wide range of new possibilities for more agile and flexible applications. However, guaranteed quality of service is essential in provisioning of cloud services, which makes Service Level Agreements (SLAs) a focal point in the cloud computing and IoT ecosystem. The SLA definition and modeling phase is crucial in establishing SLAs between service providers and consumers. This paper identifies that the research on definition and modeling of SLAs for cloud services in IoT is widely dispersed and there is a lack of a systematic and comprehensive literature review. Thus, in this paper we build on top of a previously conducted systematic mapping study on management of SLAs for cloud computing and IoT to perform a comprehensive systematic review and discuss sub-categorization of the definition and modeling aspects of SLAs for cloud services in IoT. Furthermore we analyze the extracted relevant literature, present commonalities in the studies, identify gaps and discuss opportunities for further research in the area. 

  • 15.
    Girs, Svetlana
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Sljivo, Irfan
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Jaradat, Omar
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Contract-Based Assurance for Wireless Cooperative Functions of Vehicular Systems2017In: IECON 2017 - 43RD ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY, 2017, p. 8391-8396Conference paper (Refereed)
    Abstract [en]

    Cooperation of vehicular systems is the stepping stone towards both road and indoor smart transportation systems. It aims at increasing transportation efficiency and safety compared to the stand-alone vehicular systems. The usage of wireless communication as the foundation of such safety-critical cooperation needs to be embraced with all its benefits and flaws compared to the wired communication. The cooperative functions need to be designed to adapt to the varying reliability of the wireless communication channels such that both the stand-alone vehicles as well as the smart transportation system formed by their cooperation are deemed sufficiently safe. In this paper we build upon a contract-based runtime monitoring architecture and propose a methodology for assuring adaptive behaviour of transportation with respect to the wireless communication channel failures. More specifically, we elaborate how safety analysis of the interaction of the wirelessly connected vehicles can be used as the basis for derivation of the adaptive modes and the corresponding contracts. Furthermore, we discuss how such contracts can be used as the basis for assurance of the adaptive wireless cooperation. We illustrate the proposed methodology on a smart transportation system of a factory.

  • 16.
    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.

  • 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. 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.

  • 18.
    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.

  • 19.
    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.

  • 20.
    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.

  • 21.
    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.

  • 22.
    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.

  • 23.
    Gorospe, Joseba
    et al.
    Mondragon Unibertsitatea, Spain.
    Hasan, Shahriar
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Islam, Mir Riyanul
    Mälardalen University, School of Innovation, Design and Engineering.
    Gomez, Arrate Alonso
    Mondragon Unibertsitatea, Spain.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Analyzing Inter-Vehicle Collision Predictions during Emergency Braking with Automated Vehicles2023In: International Conference on Wireless and Mobile Computing, Networking and Communications, IEEE Computer Society , 2023, Vol. 2023-June, p. 411-418Conference paper (Refereed)
    Abstract [en]

    Automated Vehicles (AVs) require sensing and perception to integrate data from multiple sources, such as cameras, lidars, and radars, to operate safely and efficiently. Collaborative sensing through wireless vehicular communications can enhance this process. However, failures in sensors and communication systems may require the vehicle to perform a safe stop or emergency braking when encountering hazards. By identifying the conditions for being able to perform emergency braking without collisions, better automation models that also consider communications need to be developed. Hence, we propose to employ Machine Learning (ML) to predict inter-vehicle collisions during emergency braking by utilizing a comprehensive dataset that has been prepared through rigorous simulations. Using simulations and data-driven modeling has several advantages over physics-based models in this case, as it, e.g., enables us to provide a dataset with varying vehicle kinematic parameters, traffic density, network load, vehicle automation controller parameters, and more. To further establish the conditions for inter-vehicle collisions, we analyze the predictions made through interpretable ML models and rank the features that contribute to collisions. We also extract human-interpretable rules that can establish the conditions leading to collisions between AVs during emergency braking. Finally, we plot the decision boundaries between different input features to separate the collision and non-collision classes and demonstrate the safe region of emergency braking.

  • 24.
    Hasan, Shahriar
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Al Ahad, Muhammed Abdullah
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Sljivo, Irfan
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Balador, Ali
    Rise Sics Västerås, Sweden.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Lisova, Elena
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    A fault-tolerant controller manager for platooning simulation2019In: 2019 8th IEEE International Conference on Connected Vehicles and Expo, ICCVE 2019 - Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2019Conference paper (Refereed)
    Abstract [en]

    Recent development in wireless technology enabling communication between vehicles led to introduction of the concept of Cooperative Adaptive Cruise Control (CACC), which uses wireless vehicle-to-vehicle communication and aims at string stable behavior in a platoon of vehicles. Degradation cascades have been proposed as a way to maintain a certain level of the system functionality in presence of failures. Such degradation behaviour is usually controlled by a runtime/state manager that performs fault detection and transitions the system into states where it will remain acceptably safe. In this paper, we propose a dynamic controller manager that focuses on both safety and performance of the system. In particular, it monitors the channel quality within the platoon and reacts by degrading platoon performance in presence of communication failures, or upgrading the performance when the communication quality is high enough. The reaction can include, e.g., adjusting the inter-vehicle distance or switching to another suitable platoon controller to prevent collisions. We focus on the functional and operational safety and evaluate the performance of the dynamic controller manager under different scenarios and settings in simulation experiments to demonstrate that it can avoid rear-end collisions in a platoon, continue platooning operation even in dense traffic scenarios where the state-of-the-art controllers fail to do so.

  • 25.
    Hasan, Shahriar
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    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.

  • 26. Hasan, Shahriar
    et al.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Characterization of Transient Communication Outages Into States to Enable Autonomous Fault Tolerance in Vehicle Platooning2023In: IEEE OPEN JOURNAL OF INTELLIGENT TRANSPORTATION SYSTEMS, ISSN 2687-7813, Vol. 4, p. 101-129Article in journal (Refereed)
    Abstract [en]

    The benefits of platooning, e.g., fuel efficiency, road throughput enhancement, driver offload, etc., have sparked an interest in a more connected, intelligent, and sustainable transportation ecosystem. However, efficient platooning is realized through wireless communications, characterized by transient connectivity, which is caused by occasional packet losses. Being a safety-critical system of systems, a platoon must be fail-operational even during transient connectivity. Moreover, a platoon should be capable of transitioning into a fail-safe state upon encountering a hazard. To this end, we propose a strategy for classifying the transient communication outages incurred by platooning vehicles into states. Furthermore, a state machine using these states to enable safe automated platooning is proposed that also defines the transitions between the states based on the nature and levels of transient connectivity and hazards. To achieve this, a graceful degradation and upgradation method is proposed, such that the platoon can remain fail-operational by adjusting, e.g., the automated controller and/or the inter-vehicle gaps based on the current communication quality. An emergency braking strategy is also proposed to enable a fast transition into a fail-safe state, should the platoon encounter a hazard. Rigorous simulation studies show that the proposed strategies enable fault-tolerant automated platooning also during transient connectivity.

  • 27.
    Hasan, Shahriar
    et al.
    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.
    Cooperative Automated Emergency Braking for CAVs under Time-Varying Communication Delays2023In: IAVVC 2023 - IEEE International Automated Vehicle Validation Conference, Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2023Conference paper (Refereed)
    Abstract [en]

    Connected and Automated Vehicles (CAVs) have the potential to significantly improve road safety, fuel efficiency, and traffic flow by forming platoons with short inter-vehicle gaps, enabled by vehicle-to-vehicle communications and onboard sensors. However, wireless connectivity for CAVs is subject to time-varying delays, which can significantly impact platoon safety during emergency braking. To this end, this paper evaluates the communication delays incurred by platoon vehicles during emergency braking under various data and traffic densities. Additionally, an emergency braking strategy named adaptive emergency braking is proposed and compared with five other strategies based on their ability to meet the functional requirements of collision avoidance and minimizing the stopping distance of the platoon lead vehicle, which are crucial for transitioning a platoon to a fail-safe state. Moreover, the emergency braking strategies are evaluated through rigorous simulations, considering non-functional criteria such as required inter-vehicle gaps, maximum allowable deceleration rates, and their robustness under time-varying communication delays. 

  • 28.
    Hasan, Shahriar
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Gorospe, J.
    Mondragon Unibertsitatea, Electronics and Computer Science Department, Arrasate, 20500, Spain.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Gomez, A. A.
    Mondragon Unibertsitatea, Electronics and Computer Science Department, Arrasate, 20500, Spain.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    PlatoonSAFE: An Integrated Simulation Tool for Evaluating Platoon Safety2023In: IEEE Open Journal of Intelligent Transportation Systems, ISSN 2687-7813, Vol. 4, p. 325-347Article in journal (Refereed)
    Abstract [en]

    Platooning is highly tractable for enabling fuel savings for autonomous and semi-autonomous cars and trucks. Safety concerns are one of the main impediments that need to be overcome before vehicle platoons can be deployed on ordinary roads despite their readily available technical feasibility. Simulation studies remain vital for evaluating platoon safety applications primarily due to the high cost of field tests. To this end, we present PlatoonSAFE, an open-source simulation tool that promotes the simulation studies of fault tolerance in platooning by enabling the monitoring of transient communication outages during runtime and assigning an appropriate performance level as a function of the instantaneous communication quality. In addition, PlatoonSAFE facilitates the simulation of several emergency braking strategies to evaluate their efficacy in transitioning a platoon to a fail-safe state. Furthermore, two Machine Learning (ML) models are integrated into PlatoonSAFE that can be employed as an onboard prediction tool in the platooning vehicles to facilitate online training of ML models and real-time prediction of communication, network, and traffic parameters. In this paper, we present the PlatoonSAFE structure, its features and implementation details, configuration parameters, and evaluation metrics required to evaluate the fault tolerance of platoon safety applications. 

  • 29.
    Hasan, Shahriar
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Gorospe, Joseba
    Mondragon Unibertsitatea, Elect & Comp Sci Dept, Arrasate Mondragon, Spain..
    Gomez, Arrate Alonso
    Mondragon Unibertsitatea, Elect & Comp Sci Dept, Arrasate Mondragon, Spain..
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Uhlemann, Elisabeth
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Prediction of Communication Delays in Connected Vehicles and Platoons2023In: 2023 IEEE 97TH VEHICULAR TECHNOLOGY CONFERENCE, VTC2023-SPRING, IEEE , 2023Conference paper (Refereed)
    Abstract [en]

    Automated vehicles connected through vehicle-tovehicle communications can use onboard sensor information from adjacent vehicles to provide higher traffic safety or passenger comfort. In particular, automated vehicles forming a platoon can enhance traffic safety by communicating before braking hard. It can also improve fuel efficiency by enabling reduced aerodynamic drag through short gaps. However, packet losses may increase the delay between periodic beacons, especially for the rear vehicles in a platoon. If the connected vehicles can forecast link quality, they can assign different performance levels in terms of intervehicle distances and also facilitate the designing of safer braking strategies. This paper proposes a strategy for incorporating machine learning algorithms into, e.g., the lead vehicle of a platoon to enable online training and real-time prediction of communication delays incurred by connected vehicles during runtime. The prediction accuracy and its suitability for making safety-critical decisions during, e.g., emergency braking have been evaluated through rigorous simulations.

  • 30.
    Lisova, Elena
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    The Challenge of Safety Tactics Synchronization for Cooperative Systems2019In: International workshop on Interplay of Security, Safety and System/Software Architecture ISSA-2018, 2019, p. 50-58Conference paper (Refereed)
    Abstract [en]

    Given rapid progress in integrating operational and industrial technologies and recent increase in the level of automation in safety-related systems, cooperative cyber-physical systems are emerging in a self-contained area requiring new approaches for addressing their critical properties such as safety and security. The notion of tactics is used to describe a relation between a system input and its corresponding response. Cooperative functionalities often rely on wireless communication and incoherent behavior of different wireless channels makes it challenging to achieve harmonization in deployment of systems' tactics. In this work we focus on safety tactics for cooperative cyber-physical systems as a response to inputs related to both safety and security, i.e., we are interested in security informed safety, and formulate a challenge of synchronization of safety tactics between the cooperating systems. To motivate the requirement on such synchronization we consider a car platoon, i.e., a set of cooperative vehicles, as an example and illustrate possible hazards arising from unsynchronized tactics deployment.

  • 31.
    Yue, Jing
    et al.
    School of Electrical and Information Engineering, The University of Sydney, Australia.
    Girs, Svetlana
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. IS (Embedded Systems).
    Åkerberg, Johan
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. ABB AB, Corporate Research, Sweden.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. IS (Embedded Systems).
    Lin, Zihuai
    School of Electrical and Information Engineering, The University of Sydney, Australia.
    Network coding for reliable downlink transmissions in industrial wireless sensor and actuator networks2016In: Proceedings of the International Symposium on Wireless Communication Systems, Poznan, Poland, 2016, Vol. oct, p. 560-565, article id 7600967Conference paper (Refereed)
    Abstract [en]

    Benefits, such as significant reduction of cost and complexity, brought by wireless communication make wireless networks more and more appealing for industrial applications. However, before wireless systems can be deployed in industrial networks, strict industrial requirements on reliability and timeliness must be fulfilled and thus protocols increasing the performance of wireless communication are needed. Data in industrial systems is typically transmitted in two directions: from sensor nodes to a controller (uplink transmission) and from the controller to actuators (downlink transmission). Several previous studies have looked at possibilities of performance increase in uplink transmissions from the sensors, while not that much work focused on downlink transmissions, which are equally important. Thus, this paper addresses the downlink transmission scenario and presents a new protocol introducing network coding into packet forwarding scheme. Simulation results show that packet reception rate can be increased when network coding is applied.

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