Abstract
The current specification of the IEEE 802.15.4 standard supports several application specific Quality of Service (QoS) requirements for Internet of Things (IoT) network applications. Specifically, the Time Slotted Channel Hopping (TSCH) MAC mode provides effective latency and throughput performance through the use of dedicated timeslots between two communicating devices. Despite the impact TSCH MAC can facilitate in low-power lossy networks (LLNs), the standard does not explore either the building or maintaining of a schedule. The challenge is to build an energy-efficient TSCH schedule that repeats periodically over several channels. To address this problem, we propose a centralized cluster-level TSCH scheduling mechanism from the energy-efficiency perspective. The proposed mechanism derives a collision graph for each of the clusters in the network topology to schedule non-overlapping timeslots. The Bron-Kerbosch algorithm is used as a sub-procedure for finding the complete sub-graphs of a graph. In addition, we analytically compute the transmission and energy overhead with the help of a Markov Model for TSCH.