Link-layer security in TSCH networks: effect on slot duration.

The IEEE802.15.4e-2012 standard is widely used in multi-hop wireless Industrial Internet of Things (IIoT)applications. In the Time-Slotted Channel Hopping (TSCH) mode, nodes are synchronized, and time iscut into timeslots. A schedule orchestrates all communications, resulting in high reliability and low poweroperations. A timeslot must be long enough for a node to send a data frame to its neighbor, and for thatneighbor to send back an acknowledgment. Shorter timeslots enable higher bandwidth and lower latency, yetthe minimal timeslot duration is limited by how long link-layer security operations take. We evaluate theoverhead of link-layer security in TSCH networks in terms of minimal timeslot length, memory footprint,and energy consumption. We implement full link-layer security on a range of hardware platforms, exploringdiu000berent hardware/software implementation strategies. Through an extensive measurement campaign, wequantify the advantage of hardware accelerations for link-layer security, and show how the minimal durationof a timeslot varies between 9 ms and 88 ms for the most common confguration, depending on hardwaresupport. Furthermore, we also highlighted the impact that the timeslot duration has on both high-levelapplication design and energy consumption.