Scheduling Transmissions with Latency Constraints in an IEEE 802.15.4e TSCH Network

Time Slotted Channel Hopping (TSCH), specified in the IEEE 802.15.4e amendment, has been designed for industrial automation, process control and equipment monitoring. It uses a slotted medium access on several channels in parallel and supports multihop communications. In this paper, we study how applications with data delivery constraints can be supported by a TSCH network. We first propose a framework based on a multislotframe that allows the coexistence of Data Slotframes and Control Slotframes. We then determine a lower bound on the minimum number of slots required to perform data gathering, taking into account the number of channels, the number of interfaces of the sink, the number of packets generated by each sensor node as well as the number of children of the sink. These feasibility conditions are established for two cases: with spatial reuse and without. We propose a debt-based scheduler that for simple topologies, provides a schedule minimizing the slotframe size. Finally, we consider a network configuration representative of an industrial application and evaluate the performance of the TSCH network in terms of data delivery delay and queue size for each sensor node, using the NS-3 simulator. Simulation results confirm the theory.