Traffic-Aware 6TiSCH Routing Method for IIoT Wireless Networks

The 6TiSCH network is a key technology of the Industrial Internet of Things (IIoT), providing high reliability and deterministic features. However, IIoT sensors and facility applications generate heavy traffic loads. Various time-slotted channel hopping (TSCH) medium access layer (MAC) and routing protocols for low-power and lossy network (RPL) methods have been studied at each network layer to address this issue. Although TSCH MAC is standard for IIoT low-rate wireless networks, it has not been adequately considered in conventional RPL studies. Conventional RPL methods do not effectively utilize the characteristics of the TSCH MAC in heavy-traffic networks and may hinder performance. In this article, we introduce a traffic-aware (TA) RPL method that utilizes the cell allocation information of TSCH MAC. The number of allocated TSCH cells determines the bandwidth reserved by each node and includes the link quality and traffic information measured by the MAC layer. TA RPL facilitates efficient load balancing using cell allocation information and improves the bandwidth utilization of the network. Additionally, the proposed method can improve the deterministic features of the IIoT wireless network because the effect of the routing decision of each device can be predicted. Moreover, the packet delivery ratio and bandwidth utilization are improved by up to 31% and 20%, respectively, compared with the conventional methods based on simulation and testbed evaluations.