| 1. |
- Elsts, Atis, et al.
(författare)
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Microsecond-Accuracy Time Synchronization Using the IEEE 802.15.4 TSCH Protocol
- 2017
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Ingår i: 2016 IEEE 41st Conference on Local Computer Networks Workshops (LCN Workshops). - : IEEE Computer Society. - 9781509023479 ; , s. 156-164
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Konferensbidrag (refereegranskat)abstract
- Time-Slotted Channel Hopping from the IEEE 802.15.4-2015 standard requires that network nodes are tightly time-synchronized. Existing implementations of TSCH on embedded hardware are characterized by tens-of-microseconds large synchronization errors; higher synchronization accuracy would enable reduction of idle listening time on receivers, in this way decreasing the energy required to run TSCH. For some applications, it would also allow to replace dedicated time synchronization mechanisms with TSCH. We show that time synchronization errors in the existing TSCH implementations on embedded hardware are caused primarily by imprecise clock drift estimations, rather than by real unpredictable drift variance. By estimating clock drift more precisely and by applying adaptive time compensation on each node in the network, we achieve microsecond accuracy time synchronization on point-to-point links and a < 2 μs end-to-end error in a 7-node line topology. Our solution is implemented in the Contiki operating system and tested on Texas Instruments CC2650-based nodes, equipped with common off-the-shelf hardware clock sources (±20 ppm drift). Our implementation uses only standard TSCH control messages and is able to keep radio duty cycle below 1 %.
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| 2. |
- Elsts, Atis, et al.
(författare)
-
Temperature-resilient time synchronization for the internet of things
- 2018
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Ingår i: IEEE Transactions on Industrial Informatics. - 1551-3203 .- 1941-0050. ; 14:5, s. 2241-2250
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Tidskriftsartikel (refereegranskat)abstract
- Networks deployed in real-world conditions have to cope with dynamic, unpredictable environmental temperature changes. These changes affect the clock rate on network nodes, and can cause faster clock de-synchronization compared to situations where devices are operating under stable temperature conditions. Wireless network protocols, such as time-slotted channel hopping (TSCH) from the IEEE 802.15.4-2015 standard, are affected by this problem, since they require tight clock synchronization among all nodes for the network to remain operational. This paper proposes a method for autonomously compensating temperature-dependent clock rate changes. After a calibration stage, nodes continuously perform temperature measurements to compensate for clock drifts at runtime. The method is implemented on low-power Internet of Things (IoT) nodes and evaluated through experiments in a temperature chamber, indoor and outdoor environments, as well as with numerical simulations. The results show that applying the method reduces the maximum synchronization error more than ten times. In this way, the method allows reduction in the total energy spent for time synchronization, which is practically relevant concern for low data rate, low energy budget TSCH networks, especially those exposed to environments with changing temperature.
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| 3. |
- Haubro, Martin, et al.
(författare)
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TSCH-over-LoRA: Long Range and Reliable IPv6 Multi-hopNetworks for the Internet of Things
- 2020
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Ingår i: Internet Technology Letters. - : Wiley. - 2476-1508.
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Tidskriftsartikel (refereegranskat)abstract
- TSCH-over-LoRa is a long range and reliable IPv6 multi-hop solution that aims atcombining the reliability of TSCH (Time-Slotted, Channel Hopping) together withthe long range capabilities of LoRa. TSCH-over-LoRa brings mesh IPv6 network-ing to LoRa devices, enabling the use of standard protocols (such as RPL, UDP, andCoAP) and long range operation to TSCH/6TiSCH industrial wireless IoT networks.We design, implement, and integrate TSCH-over-LoRa into the TSCH/6TiSCH net-working stack of the Contiki-NG operating system and experimentally demonstrateits compatibility with higher-level protocols and its resilience to interference.
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| 4. |
- Oikonomou, George, et al.
(författare)
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The Contiki-NG open source operating system for next generation IoT devices
- 2022
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Ingår i: SoftwareX. - : Elsevier B.V.. - 2352-7110. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Contiki-NG (Next Generation) is an open source, cross-platform operating system for severely constrained wireless embedded devices. It focuses on dependable (reliable and secure) low-power communications and standardised protocols, such as 6LoWPAN, IPv6, 6TiSCH, RPL, and CoAP. Its primary aims are to (i) facilitate rapid prototyping and evaluation of Internet of Things research ideas, (ii) reduce time-to-market for Internet of Things applications, and (iii) provide an easy-to-use platform for teaching embedded systems-related courses in higher education. Contiki-NG started as a fork of the Contiki OS and retains many of its original features. In this paper, we discuss the motivation behind the creation of Contiki-NG, present the most recent version (v4.7), and highlight the impact of Contiki-NG through specific examples. © 2022 The Authors
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| 5. |
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| 6. |
- Pöhls, Henrich C., et al.
(författare)
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RERUM : Building a reliable IoT upon privacy- and security- enabled smart objects
- 2014
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Ingår i: 2014 IEEE Wireless Communications and Networking Conference Workshops (WCNCW). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781479930869 ; , s. 122-127
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Konferensbidrag (refereegranskat)abstract
- The Internet of Things (IoT) provides a platform for the interconnection of a plethora of smart objects. It has been widely accepted for providing Information and Communication Technologies (ICT) applications in many ￜsmartￜ environments, such as cities, buildings, metering, and even agriculture. For several reasons though such applications have yet to achieve wide adoption; a major hurdle is the lack of user trust in the IoT and its role in everyday activities. RERUM, a recently started FP7 European Union project. aims to develop a framework which will allow IoT applications to consider security and privacy mechanisms early in their design phase, ensuring a configurable balance between reliability (requiring secure, trustworthy and precise data) and privacy (requiring data minimization for private information, like location). The RERUM framework will comprise an architecture, built upon novel network protocols and interfaces as well as the design of smart objects hardware. To highlight the challenges and evaluate the framework, RERUM will employ several Smart City application scenarios, which will be deployed and evaluated in real-world testbeds in two Smart Cities participating in the project. Here we detail the key technologies RERUM will investigate over the coming three years to reach its vision for IoT security, privacy and trust.
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