A Protocol Framework for Adaptive Real-Time Communication in Industrial Wireless Sensor and Actuator Networks
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Thesis for the degree of Doctor of Technology Sundsvall 2014 A Protocol Framework for Adaptive Real-Time Communication in Industrial Wireless Sensor and Actuator Networks Wei Shen Supervisors: Professor Tingting Zhang Professor Mikael Gidlund Department of Information and Communication Systems Mid Sweden University, SE-851 70 Sundsvall, Sweden ISSN 1652-893X Mid Sweden University Doctoral Thesis 178 ISBN 978-91-87557-31-6 Akademisk avhandling som med tillstand˚ av Mittuniversitetet i Sundsvall framlaggs¨ till offentlig granskning f or¨ avl aggande¨ av teknologie doktorsexamen, tisdagen den 06 mars 2014, klockan 13:15 i sal L111, Mittuniversitetet Sundsvall. Seminariet kommer att hallas˚ pa˚ engelska. A Protocol Framework for Adaptive Real-Time Communication in Industrial Wireless Sensor and Actuator Networks Wei Shen c Wei Shen, 2014 Department of Information and Communication Systems Mid Sweden University, SE-851 70 Sundsvall, Sweden Telephone: +46 (0)70 8569165 Printed by Kopieringen Mittuniversitetet, Sundsvall, Sweden, 2014 To My Wife iv Abstract Low-power and resource-constrained wireless technology has been regarded as an emerging technology that introduces a paradigm shift in a wide range of appli- cations such as industrial automation, smart grid, home automation and so on. The automation industry has significant contributions to economic revenues, job oppor- tunities and world-class research. The low-power and resource-constrained wireless technology has brought new opportunity and challenges for industrial automation. The solutions of such wireless technology offer benefits in relation to lower cost and more flexible deployments/maintenances than the wired solutions, and new appli- cations that are not possible with wired communication. However, these wireless solutions have been introducing new challenges. Wireless links are inherently un- reliable, especially in industrial harsh environment, and wireless interference makes the problem even worse. Low-power consumption is required and real-time com- munication is generally crucial in industrial automation applications. This research work addresses that industrial wireless sensor and actuator net- work (IWSAN) should even be designed to provide service differentiation for wire- less medium access and adapt to link dynamics for scheduling algorithms on top of real-time services. Specifically, exceeding the required delay bound for unpre- dictable and emergency traffic in industrial automation applications could lead to system instability, economic and material losses, system failure and, ultimately, a threat to human safety. Therefore, guaranteeing the timely delivery of the IWSAN critical traffic and its prioritization over regular traffic (e.g. non-critical monitoring traffic) is a significant topic. In addition, the state-of-the-art researches address a multitude of objectives for scheduling algorithms in IWSAN. However, the adapta- tion to the dynamics of a realistic wireless sensor network has not been investigated in a satisfactory manner. This is a key issue considering the challenges within indus- trial applications, given the time-constraints and harsh environments. In response to those challenges, a protocol framework for adaptive real-time com- munication in IWSAN is proposed. It mainly consists of a priority-based medium access protocol (MAC) and its extension for routing critical traffic, a hybrid scheme for acyclic traffic, and adaptive scheduling algorithms. To the best of our knowledge, the priority-based MAC solution is the first priority-enhanced MAC protocol com- patible with industrial standards for IWSAN. The proposed solutions have been im- plemented in TinyOS and evaluated on a test-bed of Telosb motes and the TOSSIM network simulator. The experimental results indicate that the proposed priority- v vi based solutions are able to efficiently handle different traffic categories and achieve a significant improvement in the delivery latency. The hybrid scheme for acyclic traffic increases the throughput and reduces the delay compared to the current industrial standards. Numerical results show that the adaptive scheduling algorithms improve the quality of service for the entire network. They achieve significant improvements for realistic dynamic wireless sensor networks when compared to existing schedul- ing algorithms with the aim to minimize latency for real-time communication. Sammanfattning Tr adl˚ osa¨ teknologier med mycket lag˚ effektf orbrukning¨ och liten minneskapacitet har blivit populara¨ sista decenniet och manga˚ nya applikationer inom olika domaner¨ som industriell automation, smarta elnat,¨ och hemautomation har m ojliggjorts.¨ Au- tomationsindustrin har lange¨ bidragit till ekonomisk tillvaxt,¨ nya arbetstillfallen¨ samt intressanta och nya sp annande¨ forskningsproblem har introducerats. Inom indus- triell automation sa˚ erbjuder tr adl˚ os¨ kommunikation en del f ordelar¨ j amf¨ ort¨ med tr adbunden˚ kommunikation genom st orre¨ flexibilitet, l agre¨ installationskostnader samt mojligheter¨ till nya applikationer som tidigare inte var m ojligt¨ med tr adbunden˚ kommunikation. Tr adl˚ os¨ kommunikation inneb ar¨ aven¨ en utmaning eftersom ra- diomiljon¨ inte ar¨ tillf orlitlig¨ i samma utstr ackning¨ som i tr adbunden˚ kommunika- tion, speciellt i industriella milj oer¨ dar¨ det kan vara mycket smuts, fukt, och interfer- ens fr an˚ andra tr adl˚ osa¨ sensorer och system. Detta forskningsarbete fokuserar pa˚ industriella tr adl˚ osa¨ sensornatverk¨ och hur man pa˚ b asta¨ satt¨ ska designa tr adl˚ osa¨ sensornatverk¨ for¨ bra tr adl˚ os¨ access i kraftigt varierande radiomiljo¨ samt algoritmer f or¨ effektiv schemal aggning¨ av real-tids app- likationer. Inom industriell automation ar¨ det viktigt att realtidskraven p a˚ datakom- munikation halls˚ for¨ att inte skapa problem i produktionsprocessen som kan leda till instabilitet i systemen, oplanerade produktionsstopp som skapar ekonomisk f orlust¨ och i absolut v arsta¨ fall skador pa˚ m anniskor.¨ D arf¨ or¨ ar¨ det av yttersta vikt att man kan garantera att datatrafiken over¨ de tr adl˚ osa¨ sensornatverken¨ haller˚ de tid- skonstanter som ar¨ givna och att viktig datatrafik prioriteras f ore¨ data f or¨ mindre kritiska applikationer som t.ex monitorering. Vidare i detta forskningsarbete s a˚ undersoks¨ schemalaggningsalgoritmer¨ for¨ industriella tr adl˚ osa¨ sensornatverk¨ som hanterar varierande radiomiljoer.¨ I denna avhandling presenteras ett ramverk f or¨ protokoll passande till indus- triella tr adl˚ osa¨ sensornatverk.¨ Fokus ligger pa˚ adaptiv schemal aggning¨ och prior- itetsbaserad accessprotokoll. De f oreslagna¨ l osningarna¨ har implementerats i TinyOS och sedan utvarderats¨ i en testb add¨ bestaende˚ av TelosB sensornoder och i TOSSIM natverkssimulator.¨ Numeriska resultat visar att adaptiv schemal aggning¨ forb¨ attrar¨ kvaliteten i hela n atverket¨ jamf¨ ort¨ med existerande algoritmer for¨ schemal aggning.¨ Speciellt visar resultaten p a˚ att man kan minska f ordr¨ ojningen¨ i de tr adl˚ osa¨ sen- sornatverken¨ med adaptiv schemalaggning.¨ Vidare s a˚ visar experimentella resultat att det foreslagna¨ prioritetsbaserade accessprotokollet p a˚ ett effektivt s att¨ hanterar datatrafik med olika prioritet pa˚ ett f ored¨ omligt¨ satt.¨ vii viii Acknowledgements First of all, I would like to thank my supervisor Prof. Tingting Zhang for her great supervisions during my PhD study. She has guided me past many obstacles in the- oretical work. Thanks to Tingting for all the guidance, suggestions and ideas on my research work during these years, and for always believing me and supporting me. Without her patience and encouragement, this thesis would not have been possible. Thanks to my co-supervisor Prof. Mikael Gidlund for all his help and guidance in my research work. He has always given me supports and encouragements what I need. I have been taught by him that thinking the academic issues from the indus- trial application point of views. Thanks to Prof. Youzhi Xu for introducing me to this opportunity to start my Ph.D. study at Mid Sweden University. Thanks to Filip Barac and Felix Dobslaw for the excellent cooperations and friendliness during my research work. Thanks to Prof. M arten˚ Sj ostr¨ om¨ for his suggestions to improve the thesis writ- ing. I would also like to thank Victor Kardeby, Stefan Forsstr om,¨ Patrik Osterberg,¨ Ulf Jennehag, Stefan Petterson, Annika Berggren and all other colleagues at the De- partment of Information and Communication Systems, Mid Sweden University for their kindness and friendliness. Last but not least, thanks to my families for their endless love and support. Spe- cial thanks to my dear wife, Jinlan Gao, for standing behind me in all that I do. This research work is financially supported by KKS COINS project (20100258), Sensible Things That Communicate (STC) and Mid Sweden University. Sundsvall, February 2014 Wei Shen ix x Contents Abstract v Sammanfattning vii Acknowledgements ix List of Papers xiii Terminology xix 1 Introduction 1 1.1 Overview . 1 1.2 Problem Description . 3 1.3 Objective and Research Topics . 4 1.4 Research Methodology . 5 1.5 Contributions . 6 1.6 Thesis Outline . 7 2 Background and Related Work 9 2.1 Low-Power and Resource-Constrained Wireless Technology . 9 2.2 Industrial Wireless Sensor and Actuator Networks . 11 2.3 Standardization Evolution of IWSAN . 14 2.4 MAC Protocols for WSN . 17 2.4.1 Fundamentals of Wireless MAC Protocols . 17 2.4.2 CSMA/CA Protocols . 21 2.4.3 MAC Protocols in Industrial Standards . 23 xi xii CONTENTS