A certifiable resource allocation for real-time multi-hop 6TiSCH wireless networks

International audienceIn safety-related industrial systems, stringent timelines and a high degree of reliability in communications are required. Networking protocols have to be certified using a mathematical framework that ascertains the end-to-end communication delay of flows is upper bounded. The recently created IETF 6TiSCH networking stack is a promising candidate to offer realtime communication services as communications are scheduled at the link layer in time and frequency. Its 6top sublayer manages the way communication resources are scheduled and thus messages routed. This paper proposes a novel certifiable resource allocation algorithm for multi-hop 6TiSCH wireless networks that simultaneously offers high reliability, low end-to-end delay and low energy consumption for safety-related industrial applications. The schedules are defined such as to directly derive a bound on the worst-case end-to-end delay. Schedules are fixed and computed by solving a multi-objective optimization problem. Two different problems are defined. The first one designs a deterministic schedule and the other one a probabilistic schedule where node are assigned a probability to forward a message in a TSCH cell. We show in our results that the latter method offers better performance in terms of robustness as possible losses due to fading are compensated for by cyclic path redundancies