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  • 1.
    Farag, Hossam
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Enabling Time- and Mission-Critical Applications in Industrial Wireless Sensor Networks2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Nowadays, Wireless Sensor Networks (WSNs) have gained importance as aflexible, easier deployment/maintenance and cost-effective alternative to wired networks,e.g., Fieldbus and Wired-HART, in a wide-range of applications. Initially,WSNs were mostly designed for military and environmental monitoringapplications where energy efficiency is the main design goal. The nodes in the network were expected to have a long lifetime with minimum maintenance while providing best-effort data delivery which is acceptable in such scenarios. With recent advances in the industrial domain, WSNs have been subsequently extended to support industrial automation applications such as process automation and control scenarios. However, these emerging applications are characterized by stringent requirements regarding reliability and real-time communications that impose challenges in the design of Industrial Wireless Sensor Networks (IWSNs) to effectively support time- and mission-critical applications.

    Typically, time- and mission-critical applications support different traffic categories ranging from relaxed requirements, such as monitoring traffic to firm requirements, such as critical safety and emergency traffic. The critical traffic is mostly acyclic in nature and occasionally occurs at unpredictable time instants. Once it is generated, it must be delivered within strict deadlines. Exceeding the delay bound could lead to system instability, economic loss, or even endanger human life in the working area. The situation becomes even more challenging when an emergency event triggers multiple sensor nodes to transmit critical traffic to the controller simultaneously. The unpredictability of the arrival of such a type of traffic introduces difficulties with regard to making a suitable scheduling that guarantees data delivery within deadline bounds. Existing industrial standards and related research work have thus far not presented a satisfactory solution to the issue. Therefore, providing deterministic and timely delivery for critical traffic and its prioritization over regular traffic is a vital research topic.

    Motivated by the aforementioned challenges, this work aims to enable real-timecommunication for time- and mission-critical applications in IWSNs. In this context, improved Medium Access Control (MAC) protocols are proposed to enablea priority-based channel access that provides a timely delivery for acyclic critical traffic. The proposed framework starts with a stochastic modelling of the network delay performance under a priority-oriented transmission scheme, followed by two MAC approaches. The first approach proposes a random Clear Channel Assessment (CCA) mechanism to improve the transmission efficiency of acyclic control traffic that is generated occasionally as a result of observations of an established tendency, such as closed-loop supervisory traffic. A Discrete-Time Markov Chain (DTMC) model is provided to evaluate the performance of the proposed protocol analytically in terms of the expected delay and throughput. Numerical results show that the proposed random CCA mechanism improves the shared slots approach in WirelessHART in terms of delay and throughput along with better transmission reliability.

    The second approach introduces a slot-stealing MAC protocol based on a dynamic deadline-aware scheduling to provide deterministic channel access in emergency and event-based situations, where multiple sensor nodes are triggered simultaneously to transmit time-critical data to the controller. The proposed protocol is evaluated mathematically to provide the worst-case delay bound for the time-critical traffic and the numerical results show that the proposed approach outperforms TDMA-based WSNs in terms of delay and channel utilization.

  • 2.
    Farag, Hossam
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Österberg, Patrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    A Delay-Bounded MAC Protocol for Mission- and Time-Critical Applications in Industrial Wireless Sensor Networks2018In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 18, no 6, p. 2607-2616Article in journal (Refereed)
    Abstract [en]

    Industrial Wireless Sensor Networks (IWSNs) designedfor mission- and time-critical applications require timelyand deterministic data delivery within stringent deadline bounds.Exceeding delay limits for such applications can lead to system malfunction or ultimately dangerous situations that can threaten human safety. In this paper, we propose SS-MAC, an efficient slot stealing MAC protocol to guarantee predictable and timely channel access for time-critical data in IWSNs. In the proposed SS-MAC, aperiodic time-critical traffic opportunistically steals time slots assigned to periodic non-critical traffic. Additionally, a dynamic deadline-based scheduling is introduced to provide guaranteed channel access in emergency and event-based situations where multiple sensor nodes are triggered simultaneously to transmit time-critical data to the controller. The proposed protocol is evaluated mathematically to provide the worst-case delay bound for the time-critical traffic. Performance comparisons are carried out between the proposed SS-MAC and WirelessHARTstandard and they show that, for the time-critical traffic, theproposed SS-MAC can achieve, at least, a reduction of almost 30% in the worst-case delay with a significant channel utilization efficiency.

  • 3.
    Farag, Hossam
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Österberg, Patrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    DeP-D: A Decentralized Primal-Dual Optimization Algorithm for Industrial Wireless Sensor Networks2019In: 2019 15th IEEE International Workshop on Factory Communication Systems (WFCS), IEEE, 2019, article id 8757934Conference paper (Refereed)
    Abstract [en]

    Industrial Wireless Sensor Networks (IWSNs) are emerged as flexible and cost-efficient alternatives to the traditional wired networks in various monitoring and control applications within the industrial domain. Low delay is a key feature of delay-sensitive applications as the data is typically valid for a short interval of time. If data arrives too late it is of limited use which may lead to performance drops or even system outages which can create significant economical losses. In this paper, we propose a decentralized optimization algorithm to minimize the End-to-End (E2E) delay of multi-hop IWSNs. Firstly, we formulate the optimization problem by considering the objective function as the network delay where the constraint is the stability criteria based on the total arrival rate and the total service rate. The objective function is proved to be strictly convex for the entire network, then a Decentralized Primal-Dual (DeP-D) algorithm is proposed based on the sub-gradient method to solve the formulated optimization problem. The performance of the proposed DeP-D is evaluated through simulations and compared with WirelessHART network and the results show that the proposed DeP-D can achieve at least 40% reduction in the average E2E delay.

  • 4.
    Farag, Hossam
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Österberg, Patrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    PR-CCA MAC: A Prioritized Random CCA MAC Protocol for Mission-Critical IoT Applications2018In: 2018 IEEE International Conference on Communications (ICC), IEEE, 2018, article id 8423018Conference paper (Refereed)
    Abstract [en]

    A fundamental challenge in Mission-Critical Internetof Things (MC-IoT) is to provide reliable and timely deliveryof the unpredictable critical traffic. In this paper, we propose an efficient prioritized Medium Access Control (MAC) protocol for Wireless Sensor Networks (WSNs) in MC-IoT control applications. The proposed protocol utilizes a random Clear Channel Assessment (CCA)-based channel access mechanism to handlethe simultaneous transmissions of critical data and to reduce thecollision probability between the contending nodes, which in turn decreases the transmission latency. We develop a Discrete-Time Markov Chain (DTMC) model to evaluate the performance of the proposed protocol analytically in terms of the expected delay and throughput. The obtained results show that the proposed protocolcan enhance the performance of the WirelessHART standard by 80% and 190% in terms of latency and throughput, respectively along with better transmission reliability.

  • 5.
    Farag, Hossam
    et al.
    Aswan University, Egypt.
    Mohamed, Ehab
    Osaka University, Japan.
    An Efficient Dynamic Thresholds Energy Detection Technique for Cognitive Radio Spectrum Sensing2014In: 10th International Computer Engineering Conference: Today Information Society What's Next?, ICENCO 2014, IEEE, 2014, p. 1623-1628Conference paper (Refereed)
    Abstract [en]

    Cognitive Radio (CR) is an intelligent technique for opportunistic access of idle resources. In CR, Spectrum sensing is one of its important key functionalities. It is used to sense the unused spectrumin an opportunistic manner. Energy detection constitutes a preferred approach for spectrum sensing in cognitive radio due to its simplicity and applicability. The conventional energy detection technique, which is based upon fixed threshold, is sensitive to noise uncertainty which is unavoidable in practical cases. This noise uncertainty gets the fixed threshold energy detector un-optimized in its performance. In this paper, an efficient energy detector is proposed for optimal CR performance. The proposed scheme is based upon a dynamic threshold energy detection algorithm, in which, the decision threshold is toggled between two levels based upon the average energy received from the primary user (PU) during a specified period of observation. Thresholds evaluations are based upon estimating the noise uncertainty factor. These thresholds are used to maximize the probability of detection (Pd) and minimize the probability of false alarm (Pfa). Theoretical analysis and simulation results show the effectiveness of the proposed scheme in comparison to the conventional energy detection method with less increase in complexity.

  • 6.
    Farag, Hossam
    et al.
    Aswan University, Egypt.
    Mohamed, Ehab M.
    Aswan University, Egypt.
    Dynamic Threshold Hard Decision Cooperative Spectrum Sensing Using Two-Stage Censoring2016In: 23rd International Conference on Telecommunications, ICT 2016, IEEE, 2016, p. 38-42Conference paper (Refereed)
    Abstract [en]

    In hard decision cooperative spectrum sensing (CSS), each secondary user (SU) or simply cognitive radio user (CR) senses the primary user (PU) activity via a Sensing channel (S-channel) and forwards its own binary decision to a fusion center (FC) via a Reporting channel (R-channel) to make a final decision regarding PU existence. In practical scenarios, both S-channels and R-channels are contaminated with noise, fading and shadowing effects. Thus, the FC may receive faulty decisions from the CRs, which in turn degrades the overall sensing performance of the cognitive radio networks (CRNs). In this paper, an efficient hard decision CSS with two-stage censoring is proposed for boosting the sensing performance of CRNs against noise uncertainty inherent in the S-channels and erroneous inherent in the R-channels. In the first stage, CRs with low quality R-channels are censored by the FC, hence only CRs with high quality R-channels are selected for the next stage of censoring. In the second stage, the low confident CRs with high noise uncertainty factors of their S-channels are censored by the FC, i.e., the FC selects the candidate CRs with the highest quality R-channels and the lowest noisy S-channels. For boosting the sensing decisions made by the CRs, a double dynamic threshold (DDT) is utilized by each CR based on an estimated value of the noise uncertainty factor of its S-channel. The new detection and false alarm probabilities are evaluated mathematically for the proposed scheme. Moreover, numerical analysis is used to confirm the high potency of the proposed scheme over some existing hard decision CSS schemes.

  • 7.
    Farag, Hossam
    et al.
    Aswan University, Egypt.
    Mohamed, Ehab M.
    Osaka University, Japan.
    Hard Decision Cooperative Spectrum Sensing Based on Estimating the Noise Uncertainty Factor2015In: Proceedings - 2015 10th International Conference on Computer Engineering and Systems, ICCES 2015, IEEE, 2015, p. 217-222Conference paper (Refereed)
    Abstract [en]

    Spectrum Sensing (SS) comprises the most important component in Cognitive Radio (CR) systems. Cooperative Spectrum Sensing (CSS) is proposed as an effective approach to improve detection performance in fading environments. This paper introduces an efficient energy detection based hard decision CSS algorithm to alleviate the noise uncertainty effect. In the proposed algorithm, the decision threshold is dynamically switched between two levels based on a prior prediction of the Primary User (PU) activity. The two threshold levels are evaluated using an estimated value of the noise uncertainty factor to maximize the probability of detection and minimize the probability of false alarm. The proposed algorithm is studied theoretically to deduce the enhanced detection and false alarm probabilities. Moreover, simulation analysis is used to confirm the theoretical claims and prove the high potency of the proposed scheme compared to the conventional CSS using different fusion rules.

  • 8.
    Farag, Hossam
    et al.
    Aswan University, Egypt.
    Mohamed, Ehab M.
    Osaka University, Japan.
    Improved Cognitive Radio Energy Detection Algorithm Based upon Noise Uncertainty Estimation2014In: National Radio Science Conference, NRSC, Proceedings, IEEE, 2014, p. 107-115Conference paper (Refereed)
    Abstract [en]

    Cognitive Radio (CR) is a regulated technique for opportunistic access of idle resources. In CR, Spectrum sensing is one of its important key functionalities. It is used to sense the unused spectrum in an opportunistic manner. Energy detection constitutes a preferred approach for spectrum sensing in cognitive radio due to its simplicity and applicability. The traditional energy detection technique, which is based upon fixed threshold, is sensitive to noise uncertainty which is unavoidable in practical cases. This noise uncertainty gets the fixed threshold energy detector un-optimized in its performance. In this paper, an efficient energy detector is proposed for optimal CR performance. The proposed scheme is a dynamic threshold energy detection algorithm, in which, two threshold levels are utilized based upon the average energy received from the primary user (PU) during a specified period of observation. Thresholds evaluations are based upon estimating the noise uncertainty factor. These thresholds are used to maximize the probability of detection (Pd) and minimize the probability of false alarm (Pfa). Theoretical analysis and simulation results show the effectiveness of the proposed scheme in comparison to the traditional energy detection method with less increase in complexity.

  • 9.
    Farag, Hossam
    et al.
    Aswan University, Egypt.
    Mohamed, Ehab M.
    Osaka University, Japan.
    Soft Decision Cooperative Spectrum Sensing Based Upon Noise Uncertainty Estimation2015In: 2015 IEEE International Conference on Communication Workshop, ICCW 2015, IEEE, 2015, p. 1623-1628Conference paper (Refereed)
    Abstract [en]

    Spectrum Sensing (SS) constitutes the most critical task in Cognitive Radio ( CR) systems for Primary User (PU) detection. Cooperative Spectrum Sensing (CSS) is introduced to enhance the detection reliability of the PU in fading environments. In this paper, we propose a soft decision based CSS algorithm using energy detection by taking into account the noise uncertainty effect. In the proposed algorithm, two threshold levels are utilized based on predicting the current PU activity, which can be successfully expected using a simple successive averaging process with time. The two threshold levels are evaluated based on estimating the noise uncertainty factor. In addition, they are toggled in a dynamic manner to compensate the noise uncertainty effect and to increase the probability of detection and decrease the probability of false alarm. Theoretical analysis is performed on the proposed algorithm to evaluate its enhanced false alarm and detection probabilities over the conventional soft decision CSS using different combining schemes. In addition, simulation results show the high efficiency of the proposed scheme compared to the conventional soft decision CSS, with high computational complexity enhancements.

  • 10.
    Farag, Hossam
    et al.
    Aswan University, Aswan, Egypt.
    Mohamed, Ehab M.
    Aswan University, Egypt; Osaka University, Japan.
    Soft Decision Cooperative Spectrum Sensing with Noise Uncertainty Reduction2017In: Pervasive and Mobile Computing, ISSN 1574-1192, E-ISSN 1873-1589, Vol. 35, p. 146-164Article in journal (Refereed)
    Abstract [en]

    Cognitive radio (CR) is a potential strategy for opportunistic access of idle resources to solve the conflicts between spectrum scarcity and underutilization. Spectrum sensing (SS) constitutes the most critical part in CR systems since the CR needs to detect the presence of primary signals reliably and quickly. Energy detection (ED) based SS is considered as the most preferable SS technique due to its simplicity and applicability. However, it is influenced by the effect of noise uncertainty which highly degrades its sensing performance. Cooperative spectrum sensing (CSS) is also introduced to mitigate some sensing problems such as multipath fading, shadowing, and hidden node problems. In this paper, we propose an enhanced fusion center (FC) rule for soft decision CSS using ED, which highly alleviates the noise uncertainty effect and enhances the sensing performance of cognitive radio networks (CRNs). In the proposed fusion rule, to increase the probability of detection and decrease the probability of false alarm, two dynamic thresholds are utilized by the FC. These thresholds are toggled based on predicting the current activity of the primary user (PU), and their values are dynamically changed based on estimating the noise uncertainty factor of the collected energy measurements from the CRs. To effectively predict (estimate) the current PU activity (the noise uncertainty factor), simple successive averaging processes over the collected energy measurements (the estimated noise variances) are performed by the FC, respectively. Theoretical analysis is performed on the proposed fusion rule for soft decision CSS to evaluate its enhanced false alarm and detection probabilities using different data combining schemes. Performance evaluations are also investigated to confirm the theoretical claims and to prove the effectiveness of the proposed scheme over the conventional ED based soft decision CSS.

  • 11.
    Farag, Hossam
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Sisinni, Emiliano
    Brescia University, Brescia, Italy.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Österberg, Patrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Priority-Aware Wireless Fieldbus Protocol for Mixed-Criticality Industrial Wireless Sensor Networks2019In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 19, no 7, p. 2767-2780Article in journal (Refereed)
    Abstract [en]

    Industrial wireless sensor networks are becoming popular for critical monitoring and control applications in industrial automation systems. For such type of applications, providing reliable real-time performance regarding data delivery is considered as a fundamental challenge. The problem becomes more prominent with mixed-criticality systems, where different data flow with different levels of criticality (importance) coexist and characterized by different requirements regarding delay and reliability. In this paper, we propose a wireless fieldbus protocol to enable real-time communication and service differentiation for cluster-based mixed-criticality networks. A process monitoring scenario of plastic extrusion is used to define the protocol requirements and elaborate the working principle of the proposed work. In our proposed protocol, each data flow is scheduled for channel access based on its criticality level using a distributed prioritized medium access mechanism that ensures a guaranteed channel access for the most critical traffic over other traffic types. The performance of the proposed protocol is analyzed analytically using a discrete-time Markov chain model to evaluate the performance in terms of delay and throughput. Moreover, the extensive simulations are conducted to prove the analytical claims and different performance assessments are provided, which also demonstrate the effectiveness of the proposed approach compared with the related existing work.

  • 12.
    Farag, Hossam
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Österberg, Patrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    RMA-RP: A Reliable Mobility-Aware Routing Protocol for Industrial IoT Networks2019Conference paper (Refereed)
    Abstract [en]

    Many emerging Industrial Internet of Things (IIoT) applications involve the use of mobile devices, such as sensors and robots in industrial automation scenarios. Movement of mobile sensor nodes causes intermittent connectivity which in turn deteriorates the network performance in terms of packet loss and delay. The Routing Protocol for Low Power and Lossy Networks (RPL) is introduced as the standard routing protocol for IIoT networks. Although RPL constitutes a reliable and energy-efficient solution for static networks, there is no mechanism defined in the RPL standard of how to support routing in mobile IIoT networks. This paper introduces RMA-RP, a reliable mobility-aware routing protocol to support mobile IIoT networks. RMA-RP utilizes a dynamic motion detection mechanism based on the link quality to cope with topology changes by updating next-hop nodes. Moreover, an adaptive timer is introduced to manage the transmission rate of control messages in order to decrease the network overhead and in turn the energy consumption. We evaluate the performance of RMA-RP through extensive simulations in comparison to existing works and the results demonstrate that RMA-RP has at least 17% higher packet delivery ratio and achieves a reduction of 34% and 51% in terms of delay and network overhead, respectively.

  • 13.
    Guntupalli, Lakshmikanth
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Farag, Hossam
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Priority-Oriented Packet Transmissions in Internet of Things: Modeling and Delay Analysis2018In: 2018 IEEE International Conference on Communications (ICC), IEEE, 2018, article id 8422699Conference paper (Refereed)
    Abstract [en]

    Priority-oriented packet transmission (PPT) has been a promising solution for transmitting time-critical packets in timely manner during emergency scenarios in Internet ofThings (IoT). In this paper, we develop two associated discrete time Markov chain (DTMC) models to analyze performance of the PPT in an IoT network. Using the proposed DTMC models, we investigate the effect of traffic prioritization interms of average packet delay for a synchronous medium access control (MAC) protocol. Furthermore, the results obtained from analytical models are validated via discrete-event simulations. Numerical results prove the accuracy of the models and reveal the behavior of priority based packet transmissions.

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