Wireless networks traditionally use a single physical layer for communication: some use high bit-rate short-range radios, others low bit-rate long-range radios. This article introduces g6TiSCH, a generalization of the standards-based IETF 6TiSCH protocol stack. g6TiSCH allows nodes equipped with multiple radios to dynamically switch between them on a link-by-link basis, as a function of link-quality. This approach results in a dynamic trade-off between latency and power consumption. We evaluate the performance of the approach experimentally on an indoor office testbed of 36 OpenMote B boards. Each OpenMote B can communicate using FSK 868 MHz, O-QPSK 2.4 GHz or OFDM 868 MHz, a combination of long-range and short-range physical layers. We measure network formation time, end-to-end reliability, end-to-end latency, and battery lifetime. We compare the performance of g6TiSCH against that of a traditional 6TiSCH stack running on each of the three physical layers. Results show that g6TiSCH yields lower latency and network formation time than any of the individual PHYs, while maintaining a similar battery lifetime.

Low-power wireless applications require different trade-off points between latency, reliability, data rate and power consumption. Given such a set of constraints, which physical layer should I be using? We study this question in the context of 6TiSCH, a state-of-the-art recently standardized protocol stack developed for harsh industrial applications. Specifically, we augment OpenWSN, the reference 6TiSCH open-source implementation, to support one of three physical layers from the IEEE802.15.4g standard: FSK 868 MHz which offers long range, OFDM 868 MHz which offers high data rate, and O-QPSK 2.4 GHz which offers more balanced performance. We run the resulting firmware on the 42-mote OpenTestbed deployed in an office environment, once for each physical layer. Performance results show that, indeed, no physical layer outperforms the other for all metrics. This article argues for combining the physical layers, rather than choosing one, in a generalized 6TiSCH architecture in which technology-agile radio chips (of which there are now many) are driven by a protocol stack which chooses the most appropriate physical layer on a frame-by-frame basis.

New radio chips implement different physical layers, allowing firmware to change modulation, datarate and frequency dynamically. This technological development is an opportunity for industrial low-power wireless networks to offer even higher determinism, including latency predictability. This article introduces 6DYN, an extension to the IETF 6TiSCH standards-based protocol stack. In a 6DYN network, nodes switch physical layer dynamically on a link-by-link basis, in order to exploit the diversity offered by this new technology agility. To offer low latency and high network capacity, 6DYN uses heterogeneous slot durations: the length of a slot in the 6TiSCH schedule depends on the physical layer used. This article shows how reserved bits in 6TiSCH headers can be used to standardize 6DYN and details its implementation in OpenWSN, a reference implementation of 6TiSCH.

As low‐power wide‐area network (LPWAN) end devices (EDs) are deployed in massive scale, their economic and environmental costs of operation are becoming too significant to ignore and too difficult to...