6TiSCH Minimal Scheduling Function: Performance Evaluation

Abstract

6TiSCH is a standardization group within the Internet Engineering Task Force (IETF) that works on IPv6-enabled Time-slotted Channel Hopping (TSCH) net- works. The 6TiSCH protocol stack, designed by the standardization work at the IETF, has direct applicability to low-power Internet of Things (IoT) use cases, including smart factory, building, infrastructure and home applications. A key component of the 6TiSCH stack is the Minimal Scheduling Function (MSF). MSF implements a traffic adaptation algorithm which allocates link-layer resources, i.e. cells in the TSCH schedule, according to the traffic load. MAX_NUMCELL is an important param- eter defined in the MSF draft standard which determines the length of the running window used to measure cell usage. MSF draft standard does not recommend a value of MAX_NUMCELL to use. This paper provides recommendations on how to choose the value of MAX_NUMCELL, validated through simulation. For periodic traf- fic, setting MAX_NUMCELL to at least 4 times the traffic load is recommended to increase efficiency. For bursty traffic, we show that setting MAX_NUMCELL to a small value achieves a low end-to-end latency but at high communication overhead. In addition, an improved version of MSF is implemented and tested, which shows a 44% reduction in the communication overhead, considering MAX_NUMCELL = 4, while maintaining the same end-to-end latency.