T۲AS: Topology/Traffic Aware Scheduling to Optimize the End-to-end Delay in IEEE۸۰۲.۱۵۴e-TSCH Networks

The Time Synchronized Channel Hopping (TSCH) mode of IEEE ۸۰۲.۱۵.۴e has been widely used as an access method for the industrial Internet of Things (IoT). It permits to overcome the performance limits of ۸۰۲.۱۵.۴ standard in such networks. It provides bounded latency and increased network capacity while mitigating the effects of interference and multipath fading. In this paper, we tackle two critical concerns of industrial networks, namely end-to-end reliability and delay by proposing two centralized scheduling mechanisms; First, the Height-based Scheduling (HS) that computes the schedule only based on the network topology. Second, T۲AS, which takes into account both traffic demand and network topology to calculate the schedule. The later mechanism uses a composite weighting function that allows scheduling links with more load and longer distance from the root in earlier timeslots. This prioritizes the flows with more traffic to be scheduled earlier. Both algorithms provide subsequential scheduling for multi-hop scenarios. Simulation results, obtained from the OpenWSN emulator, particularly confirm the efficiency of T۲AS in terms of reliability and end-to-end latency. More precisely, it guarantees a reliability of more than ۹۹% for all network sizes. Furthermore, T۲AS provides a noticeable bounded delay by delivering data packets within a single slotframe.

Keywords:

Link scheduling , ۸۰۲.۱۵.۴e-TSCH , slotframe , timeslot , cell , OpenWSN