Self-Healing Distributed Scheduling for End-to-End Delay Optimization in Multihop Wireless Networks with 6TiSCH

International audienceTime Slotted Channel Hopping (TSCH) is an amendment of the the IEEE 802.15.4 working group to provide a low-power Medium Access Control (MAC) for the Internet of Things (IoT). This standard relies on techniques such as channel hopping and bandwidth reservation to ensure both energy savings and reliable transmissions. Since many applications require low end-to-end delay (e.g. alarms), we propose here a distributed algorithm to schedule the transmissions with a short end-to-end delay. We divide the network in stratums, regrouping all the nodes with the same depth in the DODAG constructed by RPL. Then, different time-frequency blocks are assigned deterministically to each stratum. By appropriately organizing the blocks in the slotframe, we are able to deliver a packet before the end of the slotframe, whatever the route length is. We present a simple analytical study to define the initial size of each block in a homogeneous scenario. We experimentally analyze the behavior of our strategy to validate its ability to provide both high reliability and low latency in a distributed manner

Localized Scheduling for End-to-End Delay Constrained Low Power Lossy Networks with 6TiSCH

International audienceThe IoT expects to exploit IEEE802.15.4e-TSCH, designed for wireless industrial sensor networks. This standard relies on techniques such as channel hopping and bandwidth reservation to ensure both energy savings and reliable transmissions. The 6TiSCH working group currently proposes to exploit the RPL routing protocol on top of the IEEE802.15.4-2012-TSCH layer. Since many applications may require low end-to-end delay (e.g. alarms), we propose here a distributed algorithm to schedule the transmissions while upper bounding the end-to-end delay. Our strategy is based on stratums to reserve time-bands for each depth in the routing structure constructed by RPL. By allocating a sufficient number of timeslots for the possible retransmissions, we guarantee that any packet is delivered during one single slotframe, wherever the source is located. Experiments on a large scale testbed prove the relevance of this approach to reduce the end-to-end delay while minimizing the number of collisions, prejudicial to the reliability in multihop networks