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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.
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.

• 4.
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.

• 5.
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.

• 6.
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.

• 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.
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.

• 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. 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.

• 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.
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.

• 10.
Ericsson AB.
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. 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)
• 11.
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.

• 12.
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.

• 13.
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%.

• 14.
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.

• 15. Culver, Stephen
ABB Corporate Research .
Performance of Cooperative relaying with ARQ in Wireless Sensor Networks2009In: Proceedings, 2009, p. 317-319Conference paper (Refereed)
• 16.
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.

• 17.
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.

• 18.
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.

• 19.
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.

• 20.
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.

• 21.
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.

• 22.
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.

• 23.
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)
• 24.
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.

• 25.
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.

• 26.
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, 2018Conference 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.

• 27.
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.

• 28.
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, IEEE, 2018Conference 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.

• 29.
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)
• 30.
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)
• 31.
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.

• 32.
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)
• 33.
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)
• 34.
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.

• 35.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
Enhancement of HIPERLAN/2 Systems using Space-Time Coding2002In: European Wireless 2002, 2002Conference paper (Other academic)
• 36.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
On Packet Retransmission Diversity Scheme with MQAM in Fading Channels2005In: 17th Annual International Conference on Wireless Communications (Wireless 2005), 2005Conference paper (Other scientific)
• 37.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
Packet Combined ARQ Scheme Utilizing Unitary Transformation in Multiple Antenna Transmisssion2005In: Wireless Personal Multimedia Communications 2005 (WMPC'05)., IEEE , 2005Conference paper (Other scientific)
• 38.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
Performance of Coded Packet Retransmission Diversity SchemesManuscript (preprint) (Other academic)
• 39.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
Precoded closed-loop MIMO-OFDM system using predefined set of rotation matrices2005In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 41, no 5, p. 262-263Article in journal (Refereed)

Multiple-input multiple-output (MIMO) wireless systems obtain large diversity and capacity gains by employing multiple antennas at both the transmitter and receiver side. Proposed is a simple precoded closed-loop MIMO-OFDM system that improves the bit error performance. The proposed scheme only needs a feedback of two bits per OFDM tone for the entire duration of a frame.

• 40.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
Receiver-based Packet Combining in IEEE802.11a Wireless LAN2003In: Proceedings - 2003 IEEE Radio and Wireless Conference, RAWCON 2003, IEEE conference proceedings, 2003, p. 47-50, article id 1227889Conference paper (Refereed)

In this paper, we evaluate the performance of employing packet combining in 802.11a Wireless LAN (WLAN). Packet combining is well suited for WLAN since it provides a diversity gain to the system that can reduce the interference problem and enhance the system performance. Performance reults show a receiver employing packet combining provides significant gains in throughput and reductions in packet error probability compared to a system without packet combining.

• 41.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
Retransmission Diversity Schemes for Multicarrier ModulationsManuscript (Other academic)
• 42.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
STBC-based ARQ Scheme for Multiple Antenna Transmission2005In: Proceedings of the 2nd International Symposium on Wireless Communication Systems (ISWCS 2005), 2005Conference paper (Other scientific)
• 43.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
Uplink and downlink performance of OFDM signals in hybrid radio-over-fiber (RoF) links2008In: Journal of European Microwave Association, Vol. 4, no 4, p. 311-318Article in journal (Refereed)
• 44.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
ABB Corporate Research. ABB Corporate Research. ABB Corporate Research.
Wireless Communication between two temporarily connected devices2011Patent (Other (popular science, discussion, etc.))

A system for setting up a wireless connection between two temporarily connected devices (10, 12) comprises a device interconnector (14) having a first end (19) provided with a first wireless communication identifier and a second end (21) provided with a second wireless communication identifier, a first device (10) having a first interconnector mating unit (23), a first wireless communication unit (28) and a first reading unit (26) and a second device (12) having a second interconnector mating unit (31), a second wireless communication unit (34) and a second reading unit (32). The wireless communication units of each device is configured to receive an identifier being read by the corresponding reading unit as the device interconnector is attached to the corresponding mating unit and the wireless communication unit is configured to employ this identifier in setting up, together with the other wireless communication unit, a wireless connection between the two devices.

• 45.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. Acreo AB.
Acreo AB.
VoIP and IPTV distribution over wireless mesh networks in indoor environment2008In: IEEE transactions on consumer electronics, ISSN 0098-3063, E-ISSN 1558-4127, Vol. 54, no 4, p. 1665-1671Article in journal (Refereed)

Wireless mesh networks (WMNs) will play an important role in the next-generation wireless communication systems because it can support broadband services with ubiquitous coverage by low power consumption. In this article, we will discuss and evaluate the possibility of distributing triple play (Voice-over-IP (VoIP), Internet and Internet Protocol TV (IPTV)) services over a wireless meshed network established in an indoor environment. We are using modified and reconfigured IEEE 802.11b/g access points in the experimental setup. The achieved results from both simulation and experimental setup show that it is possible to run three (3) standard definition (SD) IPTV channels simultaneously and also have VoIP connected over at least two hops with satisfied quality.

• 46.
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.
Deploying a FTTH Network - Experiences from Fiber Optic Valley/Acreo Swedish National Broadband Testbed2006In: International Wire & Cable Symposium (IWCS), paper 1-5, Providence, RI, USA, Nov 2006, 2006Conference paper (Refereed)
• 47.
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.
Cost and Deployment of FTTH - Experiences from Fiber Optic Valley/Acreo Swedish National Broadband Testbed2006In: European Conference on Optical Communications (ECOC 06), We3.P.171, Cannes, France, Sept 2006, 2006Conference paper (Refereed)
• 48.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
University of Connecticut, USA. University of Brescia, Italy. Wayne State University, USA. Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
Guest Editorial From Industrial Wireless Sensor Networks to Industrial Internet of Things2018In: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 4, no 5, p. 2194-2198Article in journal (Refereed)
• 49.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
An energy efficient method for communication between a wireless sensor network and an industrial control system2011Patent (Other (popular science, discussion, etc.))

The invention is a method for communication between a wireless device node in a wireless sensor network (WSN) and control apparatus or control processes of an industrial control system (ICS). The wireless network includes a plurality of device nodes and at least one gateway (GW). The method comprises receiving at a gateway an aggregated data packet (ADP) for a final address in the ICS. The gateway processes the data packet, detects that it is an aggregated data packet and reconstructs the original data packets contained therein. The gateway then sends each of the original data packets as standard data packets to the intended final address in the ICS. In other aspects of the invention a method, system and a computer program for carrying out the method are described.

• 50.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
RISE SICS Västerås. ABB Corporate Research.
Will 5G Become Yet Another Wireless Technologyfor Industrial Automation?2017In: Proceedings of the 2017 IEEE International Conference on Industrial Technology (ICIT), IEEE, 2017, p. 1319-1324, article id 7915554Conference paper (Refereed)

With the growing interest in adoption of wireless technologies in industrial automation and the continuous search for new revenue streams new players are entering the arena in order to make their business grow further. One of the emerging wireless technologies aiming to support industrial automation applications is 5G, targeting anything from extreme throughput (>10 Gbit/s) to extreme low latency (< 1 ms) to ultra high reliability (>99.999%). In this article we intend to discuss the potential and challenges of adopting 5G in real industrial environments and give a more balanced picture compared to previous articles mainly written by telecom researchers and vendors as a way to promote their technology. Specifically, this article will discuss and provide some real industrial requirements, describe the main technical features of 5G and try to assess what applications it will support that are not by already supported by existing technologies. In the end, the success of 5G will depend on appealing business models and scalability, i.e., whether or not the same equipment can be deployed worldwide without any changes and spectrum rules, and the migration paths beyond 5G for reasonable business risks.

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