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• 1.
Uppsala Universitet.
Uppsala Universitet. Uppsala Universitet. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Long Term Channel Characterization for Energy Efficient Transmission in Industrial Environments2014In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 62, no 8, p. 3004-3014Article in journal (Refereed)

One of the challenges for a successful use of wireless sensor networks in process industries is to design networks with energy efficient transmission, to increase the lifetime of the deployed network while maintaining the required latency and bit-error rate. The design of such transmission schemes depend on the radio channel characteristics of the region. This paper presents an investigation of the statistical properties of the radio channel in a typical process industry, particularly when the network is meant to be deployed for a long time duration, e.g., days, weeks, and even months. Using 17–20-h-long extensive measurement campaigns in a rolling mill and a paper mill, we highlight the non-stationarity in the environment and quantify the ability of various distributions, given in the literature, to describe the variations on the links. Finally, we analyze the design of an optimal received signal-to-noise ratio (SNR) for the deployed nodes and show that improper selection of the distribution for modeling of the variations in the channel can lead to an overuse of energy by a factor of four or even higher.

• 2.
Uppsala University.
Uppsala University. Uppsala University. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Characterization of Long Term Channel Variations in Industrial Wireless Sensor Networks2014In: IEEE International Conference on Communications (ICC'14), IEEE conference proceedings, 2014Conference paper (Refereed)
• 3.
Frederick University, Nicosia, Cyprus.
Lancaster University, UK. Frederick University, Nicosia, Cyprus. National University of Sciences and Technology (NUST), Pakistan. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Control-Data Separation Architecture for Dual-Band mmWave Networks: A New Dimension to Spectrum Management2019In: IEEE Access, E-ISSN 2169-3536, Vol. 7, p. 34925-34937, article id 8663278Article in journal (Refereed)

The exponential growth in global mobile data traffic, especially with regards to the massive deployment of devices envisioned for the fifth generation (5G) mobile networks, has given impetus to exploring new spectrum opportunities to support the new traffic demands. The millimeter wave (mmWave) frequency band is considered as a potential candidate for alleviating the spectrum scarcity. Moreover, the concept of multi-tier networks has gained popularity, especially for dense network environments. In this article, we deviate from the conventional multi-tier networks and employ the concept of control-data separation architecture (CDSA), which comprises of a control base station (CBS) overlaying the data base station (DBS). We assume that the CBS operates on the sub-6 GHz single band, while the DBS possesses a dual-band mmWave capability, i.e., 26 GHz unlicensed band and 60 GHz licensed band. We formulate a multi-objective optimization (MOO) problem, which jointly optimizes conflicting objectives: the spectral efficiency (SE) and the energy efficiency (EE). The unique aspect of this work includes the analysis of a joint radio resource allocation algorithm based on Lagrangian Dual Decomposition (LDD) and we compare the proposed algorithm with the maximal-rate (maxRx), dynamic sub-carrier allocation (DSA) and joint power and rate adaptation (JPRA) algorithms to show the performance gains achieved by the proposed algorithm.

• 4.
Hacettepe University, Ankara, Turkey.
Hacettepe University, Ankara, Turkey. Hacettepe University, Ankara, Turkey. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
A Central Intrusion Detection System for RPL-Based Industrial Internet of Things2019In: 2019 15th IEEE International Workshop on Factory Communication Systems (WFCS), IEEE, 2019, article id 8758024Conference paper (Refereed)

Although Internet-of-Things (IoT) is revolutionizing the IT sector, it is not mature yet as several technologies are  still being offered to be candidates for supporting the backbone of this system. IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) is one of those promising candidate technologies to be adopted by IoT and Industrial IoT (IIoT). Attacks against RPL have shown to be possible, as the attackers utilize the unauthorized parent selection system of the RLP protocol. In this work, we are proposing a methodology and architecture to detect intrusions against IIoT. Especially, we are targeting to detect attacks against RPL by using genetic programming. Our results indicate that the developed framework can successfully (with high accuracy, along with high true positive and low false positive rates) detect routing attacks in RPL-based Industrial IoT networks.

• 5.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Natl Instruments Italy, I-20090 Milan, Italy. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Univ Brescia, Dept Informat Engn, I-25123 Brescia, Italy. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Channel Diagnostics for Wireless Sensor Networks in Harsh Industrial Environments2014In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 14, no 11, p. 3983-3995Article in journal (Refereed)

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.

• 6.
Ericsson AB.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. University of Brescia.
Error Manifestation in Industrial WSN Communication and Guidelines for Countermeasures2017In: Wireless Sensor Systems for Extreme Environments: Space, Underwater, Underground and Industrial / [ed] H. F. Rashvand and A. Abedi, John Wiley & Sons, 2017Chapter in book (Refereed)
• 7.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Channel Coding and Interleaving in Industrial WSN: Abiding to Timing Constraints and Bit Error Nature2013In: Proceedings - M and N 2013: 2013 IEEE International Workshop on Measurements and Networking, 2013, p. 46-51Conference paper (Refereed)

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.

• 8.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
CLAP: Chip-Level Augmentation of IEEE 802.15.4 PHY for Error-Intolerant WSN Communication2015In: IEEE Vehicular Technology Conference, Glasgow, Scotland: IEEE Vehicular Technology Society , 2015, p. 1-7Conference paper (Refereed)

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.

• 9.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
LPED: Channel Diagnostics in WSN Through Channel Coding and Symbol Error Statistics2014In: IEEE ISSNIP 2014 - 2014 IEEE 9th International Conference on Intelligent Sensors, Sensor Networks and Information Processing, Conference Proceedings, Singapore: IEEE Sensors Council, 2014, p. 1-6Conference paper (Refereed)

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.

• 10.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
PREED: Packet Recovery by Exploiting the Determinism in Industrial WSN Communication2015In: Proceedings - IEEE International Conference on Distributed Computing in Sensor Systems, DCOSS 2015, Fortaleza, Brazil: IEEE Computer Society, 2015, p. 81-90Conference paper (Refereed)

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.

• 11.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. ABB Corp Res, S-72178 Vasteras, Sweden. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Scrutinizing Bit- and Symbol-Errors of IEEE 802.15.4 Communication in Industrial Environments2014In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 63, no 7, p. 1783-1794Article in journal (Refereed)

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.

• 12.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Ubiquitous, yet Deceptive: Hardware-Based Channel Metrics on Interfered WSN Links2015In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 64, no 5, p. 1766-1778Article in journal (Refereed)

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.

• 13.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. ABB Corporate Research, Sweden. ABB Corporate Research, Sweden.
A Lightweight Routing Protocol for Industrial Wireless Sensor and Actuator Networks2011In: Proceedings of IECON 2011 - 37th Annual Conference on IEEE Industrial Electronics Society, Melbourne, Australia: IEEE Industrial Electronics Society , 2011, p. 2980-2985Conference paper (Refereed)

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.

• 14.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
Mälardalen University College, Sweden. ABB AB, Corporate Research, Sweden. ABB AB, Corporate Research, Sweden. Mälardalen University College, Sweden.
Towards Reliable and Lightweight Communication in Industrial Wireless Sensor Networks2012In: Procedings of the IEEE 10th International Conference on Industrial Informatics, INDIN 2012, IEEE conference proceedings, 2012, p. 1218-1224Conference paper (Refereed)

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.

• 15.
Indian Institute of Technology, Hyderabad, India.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University. Indian Institute of Technology, Hyderabad, India. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Indian Institute of Technology, Hyderabad, India. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Modelling and Analysis of Wi-Fi and LAA Coexistence with Priority Classes2018In: 2018 14th International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob), IEEE, 2018Conference paper (Refereed)

The Licensed Assisted Access (LAA) is shown asa required technology to avoid overcrowding of the licensedbands by the increasing cellular traffic. Proposed by 3GPP,LAA uses a Listen Before Talk (LBT) and backoff mechanismsimilar to Wi-Fi. While many mathematical models have beenproposed to study the problem of the coexistence of LAAand Wi-Fi systems, few have tackled the problem of QoSprovisioning, and in particular analysed the behaviour of thevarious classes of priority available in Wi-Fi and LAA. Thispaper presents a new mathematical model to investigate theperformance of different priority classes in coexisting Wi-Fi andLAA networks. Using Discrete Time Markov Chains, we modelthe saturation throughput of all eight priority classes used byWi-Fi and LAA. The numerical results show that with the 3GPPproposed parameters, a fair coexistence between Wi-Fi and LAAcannot be achieved. Wi-Fi users in particular suffer a significantdegradation of their performance caused by the collision withLAA transmissions which has a longer duration compared toWi-Fi transmissions.

• 16.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Modeling of Enhanced Distributed Channel Access with Station Grouping: A Throughput Analysis2018In: Proc. IEEE 88th Vehicular Technology Conference (VTC'18-fall), Chicago, USA, Aug. 2018., IEEE conference proceedings, 2018, article id 8690814Conference paper (Refereed)

Machine to Machine (M2M) communication networksare expected to connect a large number of power constrained devices in long range applications with differentquality of service (QoS) requirements. Medium access control with QoS support such as the Enhanced Distributed Channel Access (EDCA) defined by IEEE 802.11e provides traffic differentiation and corresponding priority classes, which guarantees QoSaccording to the needs of applications. In this paper, we employa station grouping mechanism for enhancing the scalability of EDCA to handle the massive number of access attempts expected in large M2M networks. Furthermore, we develop a discrete time Markov chain (DTMC) model to analyze the performance of EDCA with station grouping. Using the developed DTMC model, we calculate throughput for each access category as well as for different combinations of grouping and EDCA parameters. Thenumerical results show that the model can precisely reveal the behavior of EDCA mechanism. Moreover, it is demonstrated that employing the proposed grouping mechanism for EDCA increasesthe normalized throughput significantly for all classes of priority.

• 17.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Interference Modelling in a Multi-Cell LoRa System2018In: 2018 14th International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob), IEEE, 2018Conference paper (Refereed)

As the market for low-power wide-area network (LPWAN) technologies expands and the number of connected devices increases, it is becoming important to investigate the performance of LPWAN candidate technologies in dense deployment scenarios. In dense deployments, where the networks usually exhibit the traits of an interference-limited system, a detailed intra- and inter-cell interference analysis of LPWANs is required. In this paper, we model and analyze the performance of uplink communication of a LoRa link in a multi-cell LoRa system. To such end, we use mathematical tools from stochastic geometry and geometric probability to model the spatial distribution of LoRa devices. The model captures the effects of the density of LoRa cells and the allocation of quasi-orthogonal spreading factors (SF) on the success probability of the LoRa transmissions. To account for practical deployment of LoRa gateways, we model the spatial distribution of the gateways with a Poisson point process (PPP) and Matèrn hard-core point process (MHC). Using our analytical formulation, we find the uplink performance in terms of success probability and potential throughput for each of the available SF in LoRa’s physical layer. Our results show that in dense multi-cell LoRa deployment with uplink traffic, the intercell interference noticeably degrades the system performance.

• 18.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Hybrid MAC Mechanism for Energy Efficient Communication in IEEE 802.11ah2017In: Proceedings of the 2017 IEEE International Conference on Industrial Technology (ICIT), IEEE, 2017, p. 1295-1300, article id 7915550Conference paper (Refereed)

Many applications for machine-to-machine (M2M) communications are characterized by large numbers of devices with sporadic transmissions and subjected to low energy budgets. This work addresses the importance of energy consumption by proposing a new Medium Access Control (MAC) mechanism for improving the energy efficiency of IEEE 802.11ah, a standard targeting M2M communication. We propose to use the features of IEEE 802.11ah MAC to realize a hybrid contention-reservation mechanism for the transmission of uplink traffic. In the proposed mechanism, any device with a buffered packet will first notify the Access Point (AP) during a contention phase before being given a reserved timeslot for the data transmission. We develop a mathematical model to analyse the energy consumption ofthe proposed mechanism and of IEEE 802.11ah. The results show that for a monitoring scenario, the proposed contention reservation mechanism reduces the energy consumption for a successful uplink data transmission by up to 55%.

• 19.
University of Brescia, Italy.
Univeristy of Brescia, Italy. University of Brescia, Italy. University of Brescia, Italy. University of Brescia, Italy. University of Brescia, Italy. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. University of Brescia, Italy. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Exploiting localization systems for LoRaWAN transmission scheduling in industrial applications2019In: 2019 15th IEEE International Workshop on Factory Communication Systems (WFCS), IEEE, 2019, article id 8757999Conference paper (Refereed)

The Internet of Things (IoT) paradigm contaminated industrial world, allowing for innovative services. The wireless communications seem to be particularly attracting, especially when complement indoor and outdoor Real Time Location Systems (RTLS) for geo-referencing smart objects (e.g. for asset tracking). In this paper, the LoRaWAN solution is considered for transmitting RTLS data. LoRaWAN is an example of Low Power Wide Area Network: it tradeoffs throughput with coverage and power consumption. However, performance can be greatly improved with limited changes to the standard specifications. In this work, a scheduling layer is suggested above the regular stack for allocating communication resources in a time slot channel hopping medium access strategy. The main innovation is the time synchronization, which is obtained opportunistically from the ranging devices belonging to the RTLSs. The experimental testbed, based on commercially available solutions, demonstrates the affordability and feasibility of the proposed approach. When low-cost GPS (outdoor) and UWB (indoor) ranging devices are considered, synchronization error of few microseconds can be easily obtained. The experimental results show the that time reference pulses disciplined by GPS have a maximum jitter of 180 ns and a standard deviation of 40 ns whereas, if time reference pulses disciplined by UWB are considered, the maximum jitter is 3.3 μs and the standard deviation is 0.7 μs.

• 20.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Location Privacy Assured Internet of Things2019In: Proceedings of the 5th International Conference on Information Systems Security and Privacy / [ed] Paolo Mori, Steven Furnell and Olivier Camp, Setúbal, Portugal: SciTePress, 2019, Vol. 1, p. 623-630Conference paper (Refereed)

Internet of Things (IoT) is in the booming age of its growth, therefore a vast amount of applications, projects, hardware/software solutions, and customized concepts are being developed. The proliferation of IoT will enable location-based services to be available everywhere for everyone, and this will raise a large number of privacy issues related to the collection, usage, retention, and disclosure of the user’s location information. In order to provide a solution to this unique problem of IoT, this paper proposes Location Privacy Assured Internet of Things (LPA-IoT) scheme, which uses the concepts of Mix-Zone, location-obfuscation along with context-awareness. To the authors’ best knowledge, the proposed LPA-IoT scheme is the first location-based privacy-preserving scheme for IoT that provides flexible privacy levels associated with the present context of the user.

• 21.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Polytechnic Institute of Porto, Porto, Portugal . Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Analysis of LoRaWAN V1.1 Security2018In: Proceedings of the 4th ACM MobiHoc Workshop on Experiences with the Design and Implementation of Smart Objects (SMARTOBJECTS '18)., ACM Digital Library, 2018Conference paper (Refereed)

LoRa and the LoRaWAN specification is a technology for Low Power Wide Area Networks (LPWAN) designed to allow connectivity for connected objects, such as remote sensors. Several previous works revealed various weaknesses regarding the security of LoRaWAN v1.0 (the official 1st draft) and these led to improvements included in LoRaWAN v1.1, released on Oct 11, 2017. In this work, we provide the first look into the security of LoRaWAN v1.1. We present an overview of the protocol and, importantly, present several threats to this new version of the protocol. Besides, we propose our own ramification strategies for the mentioned threats, to be used in developing next version of LoRaWAN. The threats presented were not previously discussed, they are possible even within the security assumptions of the specification and are relevant for practitioners implementing LoRa-based applications as well researchers and the future evolution of the LoRaWAN specification.

• 22.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
School of Engineering (DEI/ISEP), Polytechnic of Porto (IPP), 4200-072 Porto, Portugal. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Security Risk Analysis of LoRaWAN and Future Directions2019In: Future Internet, ISSN 1999-5903, E-ISSN 1999-5903, Vol. 11, no 1, article id 3Article in journal (Refereed)

LoRa (along with its upper layers definition—LoRaWAN) is one of the most promising Low Power Wide Area Network (LPWAN) technologies for implementing Internet of Things (IoT)-based applications. Although being a popular technology, several works in the literature have revealed vulnerabilities and risks regarding the security of LoRaWAN v1.0 (the official 1st specification draft). The LoRa-Alliance has built upon these findings and introduced several improvements in the security and architecture of LoRa. The result of these efforts resulted in LoRaWAN v1.1, released on 11 October 2017. This work aims at reviewing and clarifying the security aspects of LoRaWAN v1.1. By following ETSI guidelines, we provide a comprehensive Security Risk Analysisof the protocol and discuss several remedies to the security risks described. A threat catalog is presented, along with discussions and analysis in view of the scale, impact, and likelihood of each threat. To the best of the authors’ knowledge, this work is one of the first of its kind, by providing a detailed security risk analysis related to the latest version of LoRaWAN. Our analysis highlights important practical threats, such as end-device physical capture, rogue gateway and self-replay, which require particular attention by developers and organizations implementing LoRa networks.

• 23. Culver, Stephen
ABB Corporate Research .
Performance of Cooperative relaying with ARQ in Wireless Sensor Networks2009In: Proceedings, 2009, p. 317-319Conference paper (Refereed)
• 24.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System science.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Challenges for the use of data aggregation in industrial Wireless Sensor Networks2015In: IEEE International Conference on Automation Science and Engineering, IEEE Computer Society, 2015, p. 138-144Conference paper (Refereed)

The provision of quality of service for Wireless Sensor Networks is more relevant than ever now where wireless solutions with their flexibility advantages are considered for the extension/substitution of wired networks for a multitude of industrial applications. Scheduling algorithms that give end-to-end guarantees for both reliability and latency exist, but according to recent investigations is the achieved quality of service insufficient for most control applications. Data aggregation is an effective tool to significantly improve on end-to-end contention and energy efficiency compared to single packet transmissions. In practice, though, it is not extensively used for process data processing on the MAC layer. In this paper, we outline the challenges for the use of data aggregation in Industrial Wireless Sensor Networks. We further extend SchedEx, a reliability-aware scheduling algorithm extension, for packet aggregation. Our simulations for scheduling algorithms from the literature show its great potential for industrial applications. Features for the inclusion of data aggregation into industrial standards such as WirelessHART are suggested, and remaining open issues for future work are presented and discussed.

• 25.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System science.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
Latency Improvement Strategies for Reliability-Aware Scheduling in Industrial Wireless Sensor Networks2015In: International Journal of Distributed Sensor Networks, ISSN 1550-1329, E-ISSN 1550-1477, article id 178368Article in journal (Refereed)

In this paper, we propose novel strategiesfor end-to-end reliability-aware scheduling in Industrial WirelessSensor Networks (IWSN). Because of stringent reliability requirements inindustrial applications where missed packets may have disastrous or lethalconsequences, all IWSN communication standards are based on TimeDivision Multiple Access (TDMA), allowing for deterministic channel access onthe MAC layer. We therefore extend an existing generic and scalablereliability-aware scheduling approach by name SchedEx. SchedEx has proven toquickly produce TDMA schedules that guarantee auser-defined end-to-end reliability level $\underline\rho$ for all multi-hopcommunication in a WSN. Moreover, SchedEx executes orders of magnitude fasterthan recent algorithms in the literature while producing schedules withcompetitive latencies.We generalize the original problem formulation from single-channel tomulti-channel scheduling and propose a scalable integration into the existingSchedEx approach.We further introduce a novel optimal bound that produces TDMAschedules with latencies around 20\% shorter than the original SchedExalgorithm. Combining the novel strategies with multiple sinks, multiplechannels, and the introduced optimal bound, we could through simulationsverify latency improvements by almost an order of magnitude, reducingthe TDMA super-frame execution times from tens of seconds to seconds only, whichallows for a utilization of SchedEx for many time-critical control applications.

• 26.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System science.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
A Reliability-Aware Cross-layer Optimization Framework for Wireless Sensor Networks.Manuscript (preprint) (Other academic)

One of the biggest obstacles for a broad deploymentof Wireless Sensor Networks for industrial applications is the dif-ficulty to ensure end-to-end reliability guarantees while providingas tight latency guarantees as possible. In response, we proposea novel centralized optimization framework for Wireless SensorNetworks that identifies TDMA schedules and routing combi-nations in an integrated manner. The framework is shown toguarantee end-to-end reliability for all events send in a schedulingframe while minimizing the delay of all packet transmissions. Itcan further be applied using alternative Quality of Service ob-jectives and constraints including energy efficiency and fairness.We consider network settings with multiple channels, multiplesinks, and stringent reliability constraints for data collectingflows. We compare the results to those achieved by the onlyscalable reliability-aware TDMA scheduling algorithm to ourknowledge, SchedEx, which conducts scheduling only. By makingrouting part of the problem and by introducing the conceptof source-aware routing, we achieve latency improvements forall topologies, with a notable average improvement of up to31percent.

• 27.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System science.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
End-to-End Reliability-aware Scheduling for Wireless Sensor Networks2016In: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 12, no 2, p. 758-767Article in journal (Refereed)

Wireless Sensor Networks (WSN) are gaining popularity as a flexible and economical alternative to field-bus installations for monitoring and control applications. For missioncritical applications, communication networks must provide endto- end reliability guarantees, posing substantial challenges for WSN. Reliability can be improved by redundancy, and is often addressed on the MAC layer by re-submission of lost packets, usually applying slotted scheduling. Recently, researchers have proposed a strategy to optimally improve the reliability of a given schedule by repeating the most rewarding slots in a schedule incrementally until a deadline. This Incrementer can be used with most scheduling algorithms but has scalability issues which narrows its usability to offline calculations of schedules, for networks that are rather static. In this paper, we introduce SchedEx, a generic heuristic scheduling algorithm extension which guarantees a user-defined end-to-end reliability. SchedEx produces competitive schedules to the existing approach, and it does that consistently more than an order of magnitude faster. The harsher the end-to-end reliability demand of the network, the better SchedEx performs compared to the Incrementer. We further show that SchedEx has a more evenly distributed improvement impact on the scheduling algorithms, whereas the Incrementer favors schedules created by certain scheduling algorithms.

• 28.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System science.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
QoS Assessment for Mission-critical Wireless Sensor Network Applications2013In: Proceedings - Conference on Local Computer Networks, LCN / [ed] Matthias Wählisch, IEEE Xplore , 2013, p. 663-666Conference paper (Refereed)

Wireless sensor networks (WSN) must ensure worst-case end-to-end delay and reliability guarantees for mission-critical applications.TDMA-based scheduling offers delay guarantees, thus it is used in industrial monitoring and automation. We propose to evolve pairs of TDMA schedule and routing-tree in a cross-layer in order to fulfill multiple conflicting QoS requirements,exemplified by latency and reliability.The genetic algorithm we utilize can be used as an analytical tool for both the feasibility and expected QoS in production. Near-optimal cross-layer solutions are found within seconds and can be directly enforced into the network.

• 29.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System science.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
QoS-Aware Cross-layer Configuration for Industrial Wireless Sensor Networks2016In: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 12, no 5, p. 1679-1691, article id 7485858Article in journal (Refereed)

In many applications of Industrial Sensor Networks, stringentreliability and maximum delay constraints paired with priority demands ona sensor-basis are present. These QoS requirements pose tough challenges forIndustrial Wireless Sensor Networks that are deployed to an ever largerextent due to their flexibility and extendibility.In this paper, we introduce an integrated cross-layer framework, SchedEx-GA, spanning MAC layer and networklayer. SchedEx-GA attempts to identify a network configuration that fulfills all application-specific process requirements over a topology including the sensorpublish rates, maximum acceptable delay, service differentiation, and eventtransport reliabilities. The network configuration comprisesthe decision for routing, as well as scheduling.

For many of the evaluatedtopologies it is not possible to find a valid configuration due to the physicalconditions of the environment. We therefore introduce a converging algorithm on top of the frameworkwhich configures a given topology by additional sink positioning in order tobuild a backbone with the gateway that guaranteesthe application specific constraints.The results show that, in order to guarantee a high end-to-end reliability of 99.999% for all flows in a network containing emergency, control loop, andmonitoring traffic, a backbone with multiple sinks is often required for thetested topologies. Additional features, such as multi-channel utilization andaggregation, though, can substantially reduce the demand for required sinks.In its present version, the framework is used for centralized control, butwith the potential to be extended for de-centralized control in future work.

• 30.
Georgia Tech.
ABB Corporate Research. NokiaSiemens Networks.
Impact of Doppler spread and adaptive modulation on TCP throughput in Rayleigh fading channels2010In: AEU - International Journal of Electronics and Communications, ISSN 1434-8411, E-ISSN 1618-0399, Vol. 64, no 11, p. 1082-1089Article in journal (Refereed)

A number of wireless systems have recently adopted adaptive modulation (AM) schemes to improve its efficiency. In this letter, our aim is to study the impact Doppler spread and adaptive modulation has on transmission control protocol (TCP) throughput in Rayleigh fading channels. We consider a finite state Markov channel (FSMC) model, which is a useful model for analyzing radio channel with nonindependent fading. Furthermore, we use a Markov model for TCP evolution and evaluate the TCP performance by computer simulations. In our simulations we have compared the TCP Reno scheme with TCP Tahoe scheme. The results indicate that a large Doppler spread leads to lower TCP throughput due to more frequent transitions of channel states and modulation schemes which make it difficult for the TCP congestion control mechanism to accommodate the dynamic link characteristics.

• 31.
Beijing Jiatong University.
Beijing Jiatong University. Beijing Jiatong University. Beijing Jiatong University. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
A Trust Management Scheme for Industrial Wireless Sensor Networks2013Conference paper (Refereed)
• 32.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Polytechnic of Porto (IPP), Porto, Portugal. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Formal security analysis of LoRaWAN2019In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 148, p. 328-339Article in journal (Refereed)

Recent Low Power Wide Area Networks (LPWAN) protocols are receiving increased attention from industry and academia to offer accessibility for Internet of Things (IoT) connected remote sensors and actuators. In this work, we present a formal study of LoRaWAN security, an increasingly popular technology, which defines the structure and operation of LPWAN networks based on the LoRa physical layer. There are previously known security vulnerabilities in LoRaWAN that lead to the proposal of several improvements, some already incorporated into the latest protocol specification. Our analysis of LoRaWAN security uses Scyther, a formal security analysis tool and focuses on the key exchange portion of versions 1.0 (released in 2015) and 1.1 (the latest, released in 2017). For version 1.0, which is still the most widely deployed version of LoRaWAN, we show that our formal model allowed to uncover weaknesses that can be related to previously reported vulnerabilities. Our model did not find weaknesses in the latest version of the protocol (v1.1), and we discuss what this means in practice for the security of LoRaWAN as well as important aspects of our model and tools employed that should be considered. The Scyther model developed provides realistic models for LoRaWAN v1.0 and v1.1 that can be used and extended to formally analyze, inspect, and explore the security features of the protocols. This, in turn, can clarify the methodology for achieving secrecy, integrity, and authentication for designers and developers interested in these LPWAN standards. We believe that our model and discussion of the protocols security properties are beneficial for both researchers and practitioners. To the best of our knowledge, this is the first work that presents a formal security analysis of LoRaWAN.

• 33.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Halmstad Högskola.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Dynamic User Authentication Protocol for Industrial IoT without Timestamping2019In: 2019 15th IEEE International Workshop on Factory Communication Systems (WFCS), IEEE, 2019, article id 8757984Conference paper (Refereed)

Internet of Things (IoT) technology has succeed ingetting a great attention in the industry where it has been ableand still can solve many industrial intractable issues. The emergingtechnology is suffering from severe security shortcomings.Authentication is a cornerstone of IoT security as it presents the measures of checking the legitimacy of communication’s entities.The Industrial IoT (IIoT) technology has special conditions, resulting from a lack of resources and a shortage of security skills. As far as we can tell, from the literature, IIoT user authentication has not been studied extensively. In 2017 Tai et al. presented an authenticated key agreement for IoT networks. Here we prove that Tai et al. is susceptible to sever security weaknesses, such as;i. stolen smart card attack, ii. unknown key share attack, iii. node capturing attack. In this research article, we offer an innovative IIoT user authentication scheme that can achieve secure remote user authentication without timestamping that requires precise synchronization, it only needs Hashing and Xor-ing. We examine the efficiency of our presented scheme using Tmote Sky node over an MSP430 microcontroller using COOJA simulator as well aswe show its correctness using Scyther verification tool.

• 34.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
The Polytechnic of Porto (IPP), Portugal. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Key Distribution Protocol for Industrial Internet of Things without Implicit Certificates2019In: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 6, no 1, p. 906-917Article in journal (Refereed)

The deployment of the Internet of Things (IoT) in industry, called the Industrial IoT (IIoT), is supporting the introduction of very desirable improvements such as increasing production flexibility, self-organization and real-time and quick response to events. However, security and privacy challenges are still to be well addressed. The IIoT requires different properties to achieve secure and reliable systems and these requirements create extra challenges considering the limited processing and communication power available to IIoT field devices. In this research article, we present a key distribution protocol for IIoT that is computationally and communicationally lightweight (requires a single message exchange) and handles node addition and revocation, as well as fast re-keying. The scheme can also resist the consequences of node capture attacks (we assume that captured nodes can be detected by the Gateway and previous works have shown this assumption to be acceptable in practice), server impersonation attacks and provides forward/backward secrecy. We show formally the correctness of our protocol and evaluate its energy consumption under realistic scenarios using a real embedded platform compared to previous state-of-the-art key-exchange protocols, to show our protocol reliability for IIoT.

• 35.
Uppsala University.
Uppsala University. Uppsala University. ABB Corporate Research.
On Hybrid ARQ Adaptive Forward Error Correction in Wireless Sensor Networks2011In: IECON 2011 - 37th Annual Conference on IEEE Industrial Electronics Society, IEEE conference proceedings, 2011, p. 3004-3010Conference paper (Refereed)

The use of wireless technology in the process industry is becoming increasingly important to obtain fast deployment at low cost. However, poor channel quality often leads to retransmissions, which are governed by Automatic Repeat Request (ARQ) schemes. While ARQ is a simple and useful tool to alleviate packet errors, it has considerable disadvantages: retransmissions lead to an increase in energy expenditure and latency. The use of Forward Error Correction (FEC) however offers several advantages. We consider a Hybrid-ARQ-Adaptive-FEC scheme (HAF) based on BCH codes and Channel State Information. This scheme is evaluated on AWGN and fading channels. It is shown that HAF offers significantly improved performance both in terms of energy efficiency and latency, as compared to ARQ.

• 36.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. 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)

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.

• 37.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. 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)

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.

• 38.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. 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)

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.

• 39.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Brescia University, Brescia, Italy. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. 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)

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.

• 40.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Lightweight Group-Key Establishment Protocol for IoT Devices: Implementation and Performance Analyses2018In: 2018 Fifth International Conference on Internet of Things: Systems, Management and Security, IEEE, 2018Conference paper (Refereed)

In the context of Internet of Things (IoT), groupcommunication is an efficient and fast way of broadcastinggroup messages. The message needs to be sent securely tomaintain confidentiality of data and privacy of users. Estab-lishing cryptographically secure communication links betweena group of transceivers requires the pre-agreement upon somekey, unknown to an external attacker. Complex and resource-intensive security schemes are infeasible for devices with limitedcomputational capabilities. In this paper, we implement alightweight and computationally secure group key establish-ment scheme suitable for resource constrained IoT networks.The proposed scheme is based on elliptic curve cryptographyand cryptographic one-way accumulators. We analyze its fea-sibility by implementing it in the Contiki operating system andsimulating it with the Cooja simulator. The simulation resultsdemonstrate the feasibility of the scheme and its computationaland communication costs are also comparable with otherexisting approaches, with an energy consumption of only 109mJ per node for group key establishment.

• 41.
University of Brescia, Italy.
University of Brescia, Italy. University of Brescia, Italy. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. University of Brescia, Italy. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
On the evaluation of LoRaWAN virtual channels orthogonality for dense distributed systems2017In: 2017 IEEE International Workshop on Measurement and Network (M&N), IEEE, 2017, p. 85-90, article id 8078371Conference paper (Refereed)

Internet of Things (IoT) aims at collecting data from billions of devices connected altogether. Despite there is no one technology able to cope with all possible scenarios, LPWAN solutions are emerging as viable technologies for implementing private, low-cost cellular like wireless networks. Distributed systems could leverage this approach as a driving technology for services as smart environment sensing, pervasive sensing and soon. In the considered scenario, the capacity of the network is of main importance; even if communication is sporadic for most of the time, an event observed by many nodes results in a huge amount of simultaneous transmissions. Are the IoT technologies usable to this end? In this paper LoRaWAN technology is investigated, with the aim of evaluating the orthogonality of virtual channels permitted by the LoRa physical layer. In particular, measurements demonstrated that overlapping transmissions having the same power at the receiver can be correctly decoded if occurring with different spreading factors, whereas co-spread messages require at least 4ms spacing.

• 42.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Challenges of Securing the Industrial Internet of Things Value Chain2018In: 2018 Workshop on Metrology for Industry 4.0 and IoT, MetroInd 4.0 and IoT 2018 - Proceedings, IEEE, 2018, p. 218-223, article id 8428344Conference paper (Refereed)

We see a shift from todays Internet-of-Things (IoT)to include more industrial equipment and metrology systems,forming the Industrial Internet of Things (IIoT). However, thisleads to many concerns related to confidentiality, integrity,availability, privacy and non-repudiation. Hence, there is a needto secure the IIoT in order to cater for a future with smart grids,smart metering, smart factories, smart cities, and smart manufacturing.It is therefore important to research IIoT technologiesand to create order in this chaos, especially when it comes tosecuring communication, resilient wireless networks, protectingindustrial data, and safely storing industrial intellectual propertyin cloud systems. This research therefore presents the challenges,needs, and requirements of industrial applications when it comesto securing IIoT systems.

• 43.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Lightweight IoT Group Key Establishment Scheme from the One Time PadManuscript (preprint) (Other academic)

Secure group communication in the Internet ofThings (IoT) entails the establishment and management of oneor more group keys to provide group security services such asconfidentiality of group messages. The main challenges in estab-lishing a group key consist in designing a group key establishmentscheme that is feasible for nodes with limited computationalcapabilities. In this paper, we propose a lightweight group keyestablishment scheme based on fast symmetric-key encryption.We show a mechanism for designing a lightweight and secure IoTgroup key establishment and management scheme whose securityis underpinned by the perfect secrecy provided by the One-time-pad. We then argue that the scheme is convenient for IoT groupapplications where nodes are resource-constrained. We prove thatour scheme is secure under a threat model where the attackerhas sufficiently large computational power. We also prove thatthe scheme provides desired group security properties such asconfidentiality, key secrecy and independent group session keysgeneration.

• 44.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Lightweight IoT Group Key Establishment Scheme Using One-way Accumulator2018In: 2018 International Symposium on Networks, Computers and Communications (ISNCC), IEEE, 2018, article id 8531034Conference paper (Refereed)

Group communication in the context of Internetof Things (IoT) is an efficient and fast way of broadcasting group messages. A message needs to be sent securely to maintain confidentiality of data and privacy of users. The main challenges in sharing group keys consist in designing and implementing a group key establishment scheme that is feasible for devices with limited computational capabilities. Existing group establishment schemes do not offer a good solution for resource-constrained IoTdevices, a solution that provides secure group key management procedures when new nodes join or leave the group without com-promising the security of the system. In this paper, we propose a light weight and computationally secure group key establishment scheme suitable for resource constrained IoT networks. The proposed scheme is based on elliptic curve cryptography and cryptographic one-way accumulators. We show how to combine the aforementioned concepts to design a group key establishment scheme that guarantees both forward and backward secrecy. Finally, we show how the established group key is updated when the group size dynamically changes and how the proposed solution can be used with block and stream ciphers.

• 45.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
A Novel Combined Packet Retransmisison Diversity and Multi-Level Modulation SchemeManuscript (preprint) (Other academic)
• 46.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
An Approach for Adaptive Error Control in Wireless LAN's with CSMA/CA MAC Protocol2002In: Proceedings of the IEEE Vehicular Technology Conference (VTC -02), 2002Conference paper (Other academic)
• 47.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
An energy efficient method for communication in a wireless sensor network of an industrial control system2011Patent (Other (popular science, discussion, etc.))

The present invention is concerned with a method forcommunication from a plurality of device nodes in a wireless sensor network of an industrial control system or a process control system. In particular the invention is concerned with a method for aggregating data packets in an energy-efficient way and wireless devices arranged with hardware and software devices for carrying out the method.

• 48.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
An Improved ARQ Scheme for Higher Level Modulation in MIMO-Systems2004In: IEEE International Conference on Communications and Information Technologies, Oct. 26-29, 2004, Sapporo, Japan., IEEE , 2004Conference paper (Other academic)
• 49.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. Acreo AB.
Combined Packet Retransmission Diversity and Power Adjustment Scheme for High Speed Wireless Networks2008In: Journal of Communications, ISSN 1796-2021, E-ISSN 1796-2021, Vol. 3, no 1, p. 56-63Article in journal (Refereed)
• 50.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
Design and Performance of Packet Retransmission Diversity Scheme for Wireless Networks2005Doctoral thesis, comprehensive summary (Other academic)

High data-rate wireless access systems are currently under discussion since the demand for wireless multimedia communication is rapidly increasing due to strong advances in wireless Internet services. Reliable high-speed data communications is one of the major challenges with regards to harsh conditions. With the necessity for high data rates, linear multi-level modulation schemes are becoming more and more important in wireless communication systems since they are bandwidth efficient. In this thesis protocols are designed and evaluated which improve system performance by combining ARQ-induced retransmissions through multipath channels in order to reduce the latency and improve the system throughput. The starting point is to show that the employment of simple packet combining schemes to wireless LANs such as IEEE 802.11, can achieve a considerable performance gain with the addition of only a small increase in complexity. A low-complexity method for enhancing and exploiting retransmission diversity by varying the bit-to-symbol mapping for each retransmission of a packet is evaluated. The selected mappings are chosen in order to maximize a bit log likelihood ratio (LLR) based metric. An ARQ scheme is also proposed, which combines retransmissions and bandwidth efficient multi-level modulation techniques with a change in the symbol mapping for every retransmission. The main idea behind this proposal is to take advantage of the extra dimension provided by a retransmission diversity scheme in improving the power efficiency if the used modulation without altering the diversity order of the system. Considering the overall scheme as one entity it is possible to obtain a transmission scheme able to perform very well in both additive Gaussian and fading channels without increase in receiver complexity. Finally, multiple antenna systems with ARQ functionality are evaluated. It has been established that using multiple antennas at both the transmitter and receiver along with intelligent signal design enables us to achieve better reliability as well as increase the transmission rate. In this thesis a space-time block coded hybrid ARQ scheme is considered which exploits both the spatial and time diversity of the MIMO channel. A bit-to-symbol mapping ARQ scheme suitable for multiple antenna systems is also considered.

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