Biblio

The Industrial Internet of Things (IIoT) paradigm represents nowadays the cornerstone of the industrial automation since it has introduced new features and services for different environments and has granted the connection of industrial machine sensors and actuators both to local processing and to the Internet. One of the most advanced network protocol stack for IoT-IIoT networks that have been developed is 6LoWPAN which supports IPv6 on top of Low-power Wireless Personal Area Networks (LoWPANs). 6LoWPAN is usually coupled with the IEEE 802.15.4 low-bitrate and low-energy MAC protocol that relies on the time-slotted channel hopping (TSCH) technique. In TSCH networks, a coordinator node synchronizes all end-devices and specifies whether (and when) they can transmit or not in order to improve their energy efficiency. In this scenario, the scheduling strategy adopted by the coordinator plays a crucial role that impacts dramatically on the network performance. In this paper, we present a novel scheduling strategy for time-slot allocation in IIoT communications which aims at the improvement of the overall network fairness. The proposed strategy mimics the well-known shell game turning the totally unfair mechanics of this game into a fair scheduling strategy. We compare our proposal with three allocation strategies, and we evaluate the fairness of each scheduler showing that our allocator outperforms the others.

Wireless Sensor Networks (WSNs) are becoming more and more popular to support a wide range of Internet of Things (IoT) applications. Time-Slotted Channel Hopping (TSCH) is a technique to enable ultra reliable and ultra low-power wireless multi-hop networks. TSCH consist of a channel hopping scheme for sending link-layer frames in different time slots and frequencies in order to efficiently combat external interference and multi-path fading. The keystone of TSCH is the scheduling algorithm, which determines for every node at which opportunity (a combination of time slots and channels) it is allowed to send. However, current scheduling algorithms are not suited for dense deployments and have important scalability limitations. In this paper, we investigate TSCH's scheduling performance in dense deployments and show how the scheduling can be improved for such environments. We performed an extensive analysis of the scalability for different scheduling approaches showing the performance drops as the number of nodes increases. Moreover, we propose a novel textlessutextgreaterDetextless/utextgreatercentralized textlessutextgreaterBrtextless/utextgreateroadcast-based textlessutextgreaterStextless/utextgreatercheduling algorithm called DeBraS, based on selective broadcasting to inform nodes about each other's schedule. Through extensive simulations, we show that DeBraS is highly more scalable than centralized solutions and that it outperforms the current decentralized 6Tisch algorithms in up to 88.5% in terms of throughput for large network sizes.