Enabling Centralized Scheduling Using Software Defined Networking in Industrial Wireless Sensor Networks

Industrial Wireless Sensor Networks (IWSN) play a key role in the Industry 4.0 revolution. The network infrastructure is critical to interconnect sensors and actuators and needs to respect Key Performance Indicators. IEEE 802.15.4-TSCH is a candidate technology for IWSN since it relies on scheduled transmissions and frequency hopping to make the network more reliable. However, distributed scheduling solutions fail to provide high reliability and low end-to-end latency. Software Defined Network (SDN) tends now to emerge in wireless networks as well, where a controller is in charge of the whole network configuration. But scheduled wireless networks require to go beyond usual SDN forwarding rules by including the radio resource allocation (dedicated time-frequency blocks). Moreover, radio links are known to be unreliable, and we need to adapt the control and data planes to make the network efficient. We propose SDN-TSCH to orchestrate a scheduled network adapting the SDN paradigm. More specifically, the controller is in charge of i) selecting the time source, ii) maintaining a tree structure for the control plane, with scheduled resources dedicated to the control plane, and iii) installing a new data flow while guaranteeing flow isolation. We also propose a very efficient link quality estimation technique tailored for scheduled TSCH networks. Our simulations highlight that the SDN controller can allocate in SDN-TSCH just-enough resources to respect both latency and reliability constraints.