BDPC: Controlling Application Delay in 6TiSCH networks for the Industrial Internet of Things

TL;DR

This paper proposes a new mechanism, called BDPC (Bounded Delay Packet Control), which combines the knowledge of a node's traffic delay to the destination (root) with the time budget of a data packet traversing the industrial IoT network, to comply the system maximum delay requirements using an adaptive and distributed algorithm.

Abstract

One of the essential requirements of wireless industrial Internet of Things (IoT) systems is to have an extremely high packet delivery rate, generally over 99.9% and comply wih realtime deadline constraints. In industrial IoT networks, packets arriving after the deadline become part of packet loss and lose meaning when they arrive late. However, currently available industial IoT proposals aim to minimize End-to-End delay without taking into account simultaneous realtime and reliability constraints. In this paper, we propose a new mechanism, called BDPC (Bounded Delay Packet Control) to tackle this challenge. BDPC combines the knowledge of a node's traffic delay to the destination (root) with the time budget of a data packet traversing the industrial IoT network, to allocate network resources to comply the system maximum delay requirements using an adaptive and distributed algorithm. Unlike the general aim to minimze end-to-end delay, we propose that data packets must arrive before the deadline, but not faster. Our results show, for example, that by using BDPC, the number of packets arriving before the deadline can be improved more than 2.6 times compared to the case when using the default Minimal Scheduling Function from the standard. As a further advantage, BDPC involves minor modifications to the 6TiSCH protocol stack, which makes it compatible with current implementations.

Figures (21)

• Figure 1: Hard and Soft Time Utility Functions. For the hard case, if the task is completed after the maximum deadline, the outcome is discarded.
• Figure 2: In the example, Node B will transmit to node A, when timeSlot 4 occurs, doing so on channelOffset 2. The Cell on coordinate [0,0] is called the Minimal-Cell, which is used for broadcast traffic.
• Figure 3: All the nodes forward traffic using a multihop topology to the destination (root) node. In the example Rank(3)$>$Rank(1) and hence, node 1 becomes the parent of node 3. The Rank value is shared among nodes using the DIO messages.
• Figure 4: 6P two-way handshake for cell assignment.
• Figure 5: 6LoRHE - Routing Header with timing information. The timing information is crucial to calculate the time budget of a data packet. The $deadline$ is carried inside the DT field.