TSCH and 6TiSCH for Contiki: Challenges, Design and Evaluation

Abstract

Abstract-Synchronized communication has recently emerged as a prime option for low-power critical applications. Solutions such as Glossy or Time Slotted Channel Hopping (TSCH) have demonstrated end-to-end reliability upwards of 99.99%. In this context, the IETF Working Group 6TiSCH is currently standardizing the mechanisms to use TSCH in low-power IPv6 scenarios. This paper identifies a number of challenges when it comes to implementing the 6TiSCH stack. It shows how these challenges can be addressed with practical solutions for locking, queuing, scheduling and other aspects.With this implementation as an enabler, we present an experimental validation and comparison with state-of-the-art MAC protocols. We conduct fine-grained energy profiling, showing the impact of link-layer security on packet transmission. We evaluate distributed time synchronization in a 340-node testbed, and demonstrate that tight synchronization (hundreds of microseconds) can be achieved at very low cost (0.3% duty cycle, 0.008% channel utilization). We finally compare TSCH against traditional MAC layers: low-power listening (LPL) and CSMA, in terms of reliability, latency and energy. We show that with proper scheduling, TSCH achieves by far the highest reliability, and outperforms LPL in both energy and latency.

Adaptive channel selection in IEEE 802.15.4 TSCH networks

“…The proposed ACS methods are compared with a baseline, unmodified Contiki implementation of TSCH [9] (Fig. 5).…”

Internet of Things for smart homes: Lessons learned from the SPHERE case study

“…The Contiki implementation of the IPv6-over-TSCH stack [6] is known to provide high end-to-end packet delivery rate (PDR): 99.99 % and more, even in challenging conditions [7]. Nevertheless, in our first testbed experiments in the SPHERE house [1], a little-interfered environment we only received 99.9 % PDR, i.e., had a ten times higher proportion of dropped packets.…”

“…Project requirements mandate that all the raw data is collected, leading to a high datarate in the IEEE 802.15.4 network: up to tens of packets per second. At the MAC layer, we use Contiki implementation [6] of the IEEE 802.15.4-2015 TSCH protocol to efficiently manage the medium access, avoid packet collisions, and synchronize time (R4). As compared to CSMA-based low-power IoT MAC protocols, TSCH provides high reliability (R6) and predictability (R7) through scheduled operation and channelhopping [7], exploiting frequency diversity to fight external interference and multipath fading.…”

Temperature-Resilient Time Synchronization for the Internet of Things

“…To avoid partitioning of the network, synchronization is always done from upstream to downstream; in particular, each downstream node marks one or more nodes as its time sources. Note that using multiple upstream nodes when they are available (e.g., in dense networks) could help to increase the synchronization quality by averaging out the errors; however, in practice, the existing TSCH open-source implementations (OpenWSN [6] and Contiki [10]) allow to have just a single upstream node as the time source.…”

“…The implementation builds on the Contiki TSCH code [10], and on the highaccuracy energy-efficient adaptive synchronization for TSCH for CC2650 described by Elsts et al in [11].…”