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  • 1.
    Barac, Filip
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för data- och systemvetenskap.
    Error mitigation in industrial wireless sensor networks: Corrupted packet forensics and recovery2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Wireless sensor networks (WSN) are gradually penetrating the industrial automation domain. This process is, however, inhibited by a number of challenges that need to be considered and addressed before WSN can serve the most demanding industrial applications. In the context of process automation, existing technology can only serve the three least critical application classes related to non-critical monitoring of slowly-changing physical variables. The main issue in that respect is the insufficient communication timeliness and reliability, caused by the influence of harsh radio environment and the infeasibility of applying advanced communication techniques, due to the poor computational power of low-cost specialized hardware. The goal of this work is to improve wireless communication reliability in industrial environments, where the proposed solutions are generally applicable to other WSN domains as well as radio environments. This research is based on the notion that corrupt packets contain valuable channel state information that can be leveraged to improve communication robustness. The research methodology used in this work is rather unconventional, compared to existing research, but also highly intuitive, bearing in mind that counteracting a phenomenon requires a thorough knowledge of its properties. In order to rectify the aforementioned challenges, this work makes the following three contributions. The first contribution is a comprehensive analysis of communication errors recorded in practically relevant scenarios in a number of industrial environments. The related literature is seemingly rich, but essentially poor, due to inadequate measurement objectives, environments, and scenarios. The main research outcome of this measurement campaign is a set of practically relevant conclusions, which can be used for the design of coding, interleaving and packet recovery schemes. The second contribution is the design of two packet recovery schemes, based on the knowledge about error patterns obtained in the industrial measurement campaign. The first scheme is a proposal for redefinition of the IEEE 802.15.4 physical layer, where digital errors are counteracted at the earliest stage in the receiver chain. The second scheme exploits the determinism in packet structure inherent to industrial communication. Both schemes significantly improve the correctability of corrupted packets received. The third contribution is a channel diagnostics algorithm that determines whether a packet was corrupt by multipath fading and attenuation or by wireless local area network interference. The algorithm is derived from the error traces collected in three industrial environments and tested at a fourth, previously unused, industrial site. The results of live tests verify the ability of the proposed algorithm to promptly reestablish communication after a sudden deterioration of channel quality.

  • 2.
    Barac, Filip
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Caiola, Stefano
    Natl Instruments Italy, I-20090 Milan, Italy.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Sisinni, Emiliano
    Univ Brescia, Dept Informat Engn, I-25123 Brescia, Italy.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Channel Diagnostics for Wireless Sensor Networks in Harsh Industrial Environments2014Ingår i: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 14, nr 11, s. 3983-3995Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wireless sensor network communication in industrial environments is compromised by interference, multipath fading, and signal attenuation. In that respect, accurate channel diagnostics is imperative to selecting the adequate countermeasures. This paper presents the lightweight packet error discriminator (LPED) that infers the wireless link condition by distinguishing between errors caused by multipath fading and attenuation, and those inflicted by interfering wideband single-channel communication systems (e.g., IEEE 802.11b/g), based on the differences in their error footprints. The LPED uses forward error correction in a novel context, namely, to determine the symbol error density, which is then fed to a discriminator for error source classification. The classification criteria are derived from an extensive set of error traces collected in three different types of industrial environments, and verified on a newly collected set of error traces. The proposed solution is evaluated both offline and online, in terms of classification accuracy, speed of channel diagnostics, and execution time. The results show that in ≥91% of cases, a single packet is sufficient for a correct channel diagnosis, accelerating link state inference by at least 270%, compared with the relevant state-of-the-art approaches. The execution time of LPED, for the worst case of packet corruption and maximum packet size, is below 30 ms with ≤3% of device memory consumption. Finally, live tests in an industrial environment show that LPED quickly recovers from link outage, by losing up to two packets on average, which is only one packet above the theoretical minimum.

  • 3.
    Barac, Filip
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Channel Coding and Interleaving in Industrial WSN: Abiding to Timing Constraints and Bit Error Nature2013Ingår i: Proceedings - M and N 2013: 2013 IEEE International Workshop on Measurements and Networking, 2013, s. 46-51Konferensbidrag (Refereegranskat)
    Abstract [en]

    Forward Error Correction is a preemptive manner of improving communication reliability. Albeit not a part of IEEE 802.15.4-2006 standard, its application in Industrial Wireless Sensor Networks has been widely considered. Nevertheless, this study is the first performance analysis on real error traces with sufficiently lightweight channel codes, with respect to IEEE 802.15.4-2006 and industrial wireless communication timing constraints. Based on these constraints and bit error properties from the collected traces, the use of Reed-Solomon (15,7) block code is suggested, which can be implemented in software. Experiments show that bit error nature on links affected by multipath fading and attenuation in industrial environments is such that RS(15,7) can correct ≥95% of erroneously received packets, without the necessity for interleaving. On links under IEEE 802.11 interference, typically up to 50% of corrupted packets can be recovered by combining RS(15,7) with symbol interleaving, which has proven to be more effective than its bit counterpart. The optimal interleaving depth is found empirically and it is shown that simple bit-interleaved 1/3 repetition code achieves at least 90% of correcting performance of RS(15,7) code on uninterfered links that operate ≥10 dB above the sensitivity threshold.

  • 4.
    Barac, Filip
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    CLAP: Chip-Level Augmentation of IEEE 802.15.4 PHY for Error-Intolerant WSN Communication2015Ingår i: IEEE Vehicular Technology Conference, Glasgow, Scotland: IEEE Vehicular Technology Society , 2015, s. 1-7Konferensbidrag (Refereegranskat)
    Abstract [en]

    Communication reliability is the ultimate priority in safety-critical wireless sensor network (WSN) communication. Surprisingly enough, the enormous potential of error control on direct sequence spread spectrum (DSSS) chips in IEEE 802.15.4 has been completely overlooked by the WSN community, possibly due to incorrect presumptions, such as the concerns about computational overhead. Current error-correction schemes in WSN counteract the error process once the errors have already propagated to bit- and packet-level. Motivated by the notion that errors should be confronted at the earliest stage, this work presents CLAP, a novel method that tremendously improves the error correction in WSN by fortifying the IEEE 802.15.4 Physical layer (PHY) with straightforward manipulations of DSSS chips. CLAP is implemented on a software-defined radio platform, and evaluated on real error traces from heavily WLAN-interfered IEEE 802.15.4 transmissions at 3 different environments. CLAP boosts the number of corrected packets by 1.78-6.88 times on severely interfered links, compared to two other state-of-the-art schemes. The overhead in terms of computational complexity is about 10% of execution time of the OQPSK demodulator in the legacy IEEE 802.15.4 receiver chain.

  • 5.
    Barac, Filip
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    LPED: Channel Diagnostics in WSN Through Channel Coding and Symbol Error Statistics2014Ingår i: IEEE ISSNIP 2014 - 2014 IEEE 9th International Conference on Intelligent Sensors, Sensor Networks and Information Processing, Conference Proceedings, Singapore: IEEE Sensors Council, 2014, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    Three major obstacles to wireless communication are electromagnetic interference, multipath fading and signal attenuation. The former stems mainly from collocated wireless systems operating in the same frequency band, while the latter two originate from physical properties of the environment. Identifying the source of packet corruption and loss is crucial, since the adequate countermeasures for different types of threats are essentially different. This problem is especially pronounced in industrial monitoring and control applications, where IEEE 802.15.4 communication is expected to deliver data within tight deadlines, with minimal packet loss. This work presents the Lightweight Packet Error Discriminator (LPED) that distinguishes between errors caused by multipath fading and attenuation, and those inflicted by IEEE 802.11 interference. LPED uses Forward Error Correction to determine the symbol error positions inside erroneously received packets and calculates the error density, which is then fed to a discriminator for error source classification. The statistical constituents of LPED are obtained from an extensive measurement campaign in two different types of industrial environments. The classifier incurs no overhead and in ≥90% of cases a single packet is sufficient for a correct channel diagnosis. Experiments show that LPED accelerates link diagnostics by at least 190%, compared to the relevant state-of-the-art approaches.

  • 6.
    Barac, Filip
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    PREED: Packet Recovery by Exploiting the Determinism in Industrial WSN Communication2015Ingår i: Proceedings - IEEE International Conference on Distributed Computing in Sensor Systems, DCOSS 2015, Fortaleza, Brazil: IEEE Computer Society, 2015, s. 81-90Konferensbidrag (Refereegranskat)
    Abstract [en]

    The requirements of safety-critical wireless sensornetwork (WSN) applications, such as closed-loop control andtraffic safety, cannot be met by the IEEE 802.15.4-2006 standardnor its industrial WSN (IWSN) derivatives. The main problem inthat respect is the communication reliability, which is seriouslycompromised by 2.4-GHz interference, as well as multipathfading and attenuation (MFA) at industrial facilities. Meanwhile,communication blackouts in critical WSN applications maylead to devastating consequences, including production halts,damage to production assets and can pose a threat to safetyof human personnel. This work presents PREED, a method toimprove the reliability by exploiting the determinism in IWSNcommunication. The proposed solution is based on the analysisof bit error traces collected in real transmissions at four differentindustrial environments. A case study on WirelessHART packetformat shows that PREED recovers 42%-134% more packetsthan the competing approaches on links compromised by WLANinterference. In addition, PREED reduces one of the most trivialcauses of packet loss in IWSN, i.e. the corruption offrame lengthbyte, by 88% and 99%, for links exposed to WLAN interferenceand MFA, respectively.

  • 7.
    Barac, Filip
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem. ABB Corp Res, S-72178 Vasteras, Sweden.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Scrutinizing Bit- and Symbol-Errors of IEEE 802.15.4 Communication in Industrial Environments2014Ingår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 63, nr 7, s. 1783-1794Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The knowledge of error nature in wireless channels is an essential constituent of efficient communication protocol design. To this end, this paper is the first comprehensive bit- and symbol-level analysis of IEEE 802.15.4 transmission errors in industrial environments. The intention with this paper is to extract the error properties relevant for future improvements of wireless communication reliability and coexistence of radio systems in these harsh conditions. An extensive set of bit-error traces was collected in a variety of scenarios and industrial environments, showing that error behavior is highly dependent on the cause of packet corruption. It is shown that errors inflicted by multipath fading and attenuation exhibit different properties than those imposed by IEEE 802.11 interference. The statistical behavior of these two patterns is concurrently investigated in terms of differences in bit-error distribution, error burst length, channel memory length, and the scale of packet corruption. With these conclusions at hand, abiding to the computational constraints of embedded sensors and the statistical properties of bit-errors, a Reed-Solomon $(15,k)$ block code is chosen to investigate the implications of bit-error nature on practical aspects of channel coding and interleaving. This paper is concluded by a number of findings of high practical relevance, concerning the optimal type, depth, and meaningfulness of interleaving.

  • 8.
    Barac, Filip
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Ubiquitous, yet Deceptive: Hardware-Based Channel Metrics on Interfered WSN Links2015Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 64, nr 5, s. 1766-1778Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ease of acquiring hardware-based link quality indicators is an alluring property for fast channel estimation in time- and safety-critical Wireless Sensor Network (WSN) applications, such as closed-loop control and interlocking. The two rudimentary hardware-based channel quality metrics, Received Signal Strength (RSS) and Link Quality Indicator (LQI), are the key constituents of channel estimation and a plethora of other WSN functionalities, from routing to transmit power control. Nevertheless, this study highlights three deficient aspects of these two indicators: 1) overall deceptiveness, i.e. the inability to reveal the presence of interference, falsely indicating excellent channel conditions in an unacceptably high fraction of cases; 2) the burstiness of missed detections, which compromises the attempts to eliminate the deceptiveness by averaging; 3) high mutual discrepancy of the two indicators, observed in 39-73% of packets, throughout different scenarios. The ability of RSS and LQI to indicate IEEE 802.11 interference is scrutinized in a variety of scenarios in typical industrial environments, using commercialoff- the-shelf hardware and realistic network topologies, giving the findings of this study a high general validity and practical relevance.

  • 9.
    Barac, Filip
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier. ABB Corporate Research, Sweden.
    Åkerberg, Johan
    ABB Corporate Research, Sweden.
    A Lightweight Routing Protocol for Industrial Wireless Sensor and Actuator Networks2011Ingår i: Proceedings of IECON 2011 - 37th Annual Conference on IEEE Industrial Electronics Society, Melbourne, Australia: IEEE Industrial Electronics Society , 2011, s. 2980-2985Konferensbidrag (Refereegranskat)
    Abstract [en]

    The applications of Industrial Wireless Sensor and Actuator Networks (IWSAN) are time-critical and subject to strict requirements in terms of end-to-end delay and reliability of data delivery. A notable shortcoming of the existing wireless industrial communication standards is the existence of overcomplicated routing protocols, whose adequacy for the intended applications is questionable [1]. This paper evaluates the potentials of flooding as a data dissemination technique in IWSANs. The concept of flooding is recycled by introducing minimal modifications to its generic form and compared with a number of existing WSN protocols, in a variety of scenarios. The simulation results of all scenarios observed show that our lightweight approach is able to meet stringent performance requirements for networks of considerable sizes. Furthermore, it is shown that this solution significantly outperforms a number of conventional WSN routing protocols in all categories of interest.

  • 10.
    Barac, Filip
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Yu, Kan
    Mälardalen University College, Sweden.
    Gidlund, Mikael
    ABB AB, Corporate Research, Sweden.
    Åkerberg, Johan
    ABB AB, Corporate Research, Sweden.
    Björkman, Mats
    Mälardalen University College, Sweden.
    Towards Reliable and Lightweight Communication in Industrial Wireless Sensor Networks2012Ingår i: Procedings of the IEEE 10th International Conference on Industrial Informatics, INDIN 2012, IEEE conference proceedings, 2012, s. 1218-1224Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 11.
    Grimaldi, Simone
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Lennvall, Tomas
    ABB AB, Corporate Research, Sweden.
    Barac, Filip
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Detecting Communication Blackout in Industrial Wireless Sensor Networks2016Ingår i: IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS, 2016, artikel-id 7496502Konferensbidrag (Refereegranskat)
    Abstract [en]

    Communication blackout is one of the most serious pitfalls of Wireless Sensor Networks (WSN) in industrial automation context. The industrial radio channel exhibits pronounced effects of multipath fading and wireless LAN (WLAN) interference that can potentially lead to temporary communication failures, as well as complete isolation of network devices. The current IWSN standards adopt known countermeasures to cope with the harshness of the radio channel, but they lack solutions specifically oriented to detect blackouts and self-recover the communication fulfilling hard deadline constraints. In this work we focus onthe problem of blackout detection with specific interest for the WirelessHART standard, introducing a Blackout Detection Service (BDS) expressly addressed to multi-hop periodic communicationwith sensors and actuators. The BDS monitors end-to-end acknowledgement messages and builds specific metrics to promptly identify communication outages, enabling three criticality classes. The algorithm is tested in the ns-2 network simulator and results show that the proposed system is able to detect blackout events with reaction delays of the order of 4-5 times the refresh rate of nodes and to discriminate between smalland temporary network issues and serious blackout scenarios, opening the field for recovery strategies.

  • 12.
    Lavassani, Mehrzad
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Barac, Filip
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Handling Event-Triggered Traffic of Safety and Closed-Loop Control Systems in WSANs2016Ingår i: 14th IEEE International Conference on Industrial Informatics (INDIN'16), IEEE, 2016, s. 631-636, artikel-id 7819237Konferensbidrag (Refereegranskat)
  • 13.
    Shen, Wei
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för data- och systemvetenskap.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för data- och systemvetenskap.
    Barac, Filip
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för data- och systemvetenskap.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för data- och systemvetenskap. ABB Corporate Research, SE-72178 Vasteras, Sweden.
    PriorityMAC: A Priority-Enhanced MAC Protocol for Critical Traffic in Industrial Wireless Sensor and Actuator Networks2014Ingår i: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 10, nr 1, s. 824-835Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper proposes PriorityMAC, a priority-enhanced medium access control protocol, designed for critical traffic in industrial wireless sensor and actuator networks (IWSAN). A notable trend in industrial automation in recent years has been the replacement of wired communication by IWSANs. Exceeding the required delay bound for unpredictable and emergency traffic could lead to system instability, economic and material losses, system failure, and, ultimately, a threat to human safety. Guaranteeing the timely delivery of the IWSAN critical traffic and its prioritization over regular traffic (e.g., noncritical monitoring traffic) is a significant challenge. Therefore, we present the design, implementation, performance analysis, and evaluation of PriorityMAC. A series of novel mechanisms (e.g., high priority indication space) are proposed to enable high-priority traffic to hijack the transmission bandwidth of the low-priority traffic. To the best of our knowledge, this is the first priority-enhanced MAC protocol compatible with industrial standards for IWSAN. PriorityMAC is implemented in TinyOS and evaluated on a testbed of Telosb motes. The experimental results indicate that PriorityMAC efficiently handles different traffic categories with different latency requirements, thereby achieving a significant improvement in the delivery latency compared with the current industrial standards. © 2005-2012 IEEE.

  • 14.
    Sisinni, E.
    et al.
    DII - Dept. of Information Engineering, University of Brescia, Brescia (BS), Italy .
    Caiola, S.
    DII - Dept. of Information Engineering, University of Brescia, Brescia (BS), Italy .
    Flammini, A.
    DII - Dept. of Information Engineering, University of Brescia, Brescia (BS), Italy .
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Barac, Filip
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Simple interference detection and classification for industrial Wireless Sensor Networks2015Ingår i: Conference Record - IEEE Instrumentation and Measurement Technology Conference, Pisa, Italy: IEEE, 2015, s. 2106-2110Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wireless Sensor Networks (WSNs) are increasingly deployed in office blocks, residential areas and also industrial locations, thanks to advantages in terms of flexibility and scalability. Nowadays available wireless fieldbuses are widely adopted for process monitoring and offer performance comparable with the wired counterparts, despite they still are more sensitive to interference from external sources. This work investigates the main sources of interference in the 2.4 GHz ISMband and evaluates the adoption of a simple algorithm to identify the interference. The proposed technique, called LPED, is based on bit error nature and forward error correction. The required computational effort is compatible with resources normally available in WSN nodes, as experimentally verified. In addition, performance in presence of IEEE802.11 and iWLAN is also verified; classification is correct in about 90% of cases.

  • 15.
    Wang, Y.
    et al.
    School of Electronics and Information Engineering, Beijing Jiaotong University, Beijing, China .
    Barac, Filip
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Implementation of the WirelessHART MAC layer in the OPNET simulator2013Ingår i: Proceedings of 2013 3rd International Conference on Computer Science and Network Technology, ICCSNT 2013, IEEE conference proceedings, 2013, s. 663-668Konferensbidrag (Refereegranskat)
    Abstract [en]

    WirelessHART standard is the first international standard for Industrial Wireless Sensor Networks (IWSN) approved by International Electrotechnical Commission (IEC), and, as such, it is worthwhile to implement on simulator platforms. Based on the study of WirelessHART standard, this paper is a primary implementation of the Medium Access Control layer of WirelessHART standard. To our best knowledge, this is the first comprehensive implementation of WirelessHART using the OPNET simulator. This paper also proposes the improvement of shared slot access method by using slotted Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA), which outperforms the existing slotted ALOHA by increasing the throughput for 2% and reducing the packet loss. Flexible dedicated slot assignment has also been proposed to reduce the packet loss rate caused by influences of the physical channel.

  • 16.
    Yu, Kan
    et al.
    Mälardalens Högskola.
    Barac, Filip
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Gidlund, Mikael
    ABB Corporate Research.
    Åkerberg, Johan
    ABB Corporate Research.
    Adaptive Forward Error Correction for Industrial Wireless Sensor Networks2012Ingår i: Proceedings, Ottawa, Canada: IEEE Communications Society, 2012, s. 7104-7109Konferensbidrag (Refereegranskat)
  • 17.
    Yu, Kan
    et al.
    Mälardalen University.
    Barac, Filip
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Gidlund, Mikael
    ABB AB, Corporate Research, Sweden.
    Åkerberg, Johan
    ABB AB, Corporate Research, Sweden.
    Björkman, Mats
    Mälardalen University, Sweden.
    A Flexible Error Correction Scheme for IEEE 802.15.4-based Industrial Wireless Sensor Networks2012Ingår i: IEEE International Symposium on Industrial Electronics, IEEE conference proceedings, 2012, s. 1172-1177Konferensbidrag (Refereegranskat)
    Abstract [en]

    Noise and interference make a substantial impacton wireless transmissions in industrial environments, resulting infrequent erroneous packet deliveries. Existing industrial communicationstandards adopt the IEEE 802.15.4 specification, whichprovides no means to correct the detected errors. We proposean IEEE 802.15.4-compliant Forward Error Correction-basedapproach that can be easily retrofitted into the standard withoutthe need for any kind of interaction with chip manufacturers orstandardization bodies. We evaluate the approach on link- andnetwork-level scenarios. Improvement of reliability by using FECcan yield multiple benefits: a reduced number of retransmissions,and lower average latency, to name a few. With respect to theuncoded system, the proposed solution provides identical codinggain as the traditional FEC method, at a significantly lowercomputational load of decoding

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