Latency Improvement Strategies for Reliability-Aware Scheduling in Industrial Wireless Sensor Networks

We propose novel strategies for end-to-end reliability-aware scheduling in IndustrialWireless Sensor Networks (IWSNs). Because of stringent reliability requirements in industrial applications where missed packets may have disastrous or lethal consequences, all IWSN communication standards are based on Time Division Multiple Access (TDMA), allowing for deterministic channel access on the MAC layer. We therefore extend an existing generic and scalable reliability-aware scheduling approach by the name of SchedEx. SchedEx has proven to quickly produce TDMA schedules that guarantee a user-defined end-to-end reliability level.. for all multihop communication in a WSN. Moreover, SchedEx executes orders of magnitude faster than recent algorithms in the literature while producing schedules with competitive latencies. We generalize the original problem formulation from single-channel to multichannel scheduling and propose a scalable integration into the existing SchedEx approach. We further introduce a novel optimal bound that produces TDMA schedules with latencies around 20% shorter than the original SchedEx algorithm. Combining the novel strategies with multiple sinks, multiple channels, and the introduced optimal bound, we could through simulations verify latency improvements by almost an order of magnitude, reducing the TDMA superframe execution times from tens of seconds to seconds only, which allows for a utilization of SchedEx for many time-critical control applications.