# Efficient Route Management Method for Mobile Nodes in 6 TiSCH Network
## 2 Background
### Tsch  
IEEE 802.15.4e time slotted channel hopping (TSCH) is one of the media access control (MAC) operating modes of the IEEE 802.15.4e standard protocol for industrial wireless sensor networks such as existing WirelessHART [14] or ISA100.11a [15]. The standard protocol provides high reliability and stability. Through media access control technology that divides time into time slots, and conflicts or contentions that may occur during wireless communication are resolved. In addition, through channel hopping technology, the multipath fading problem can be solved by preventing collisions because of an increase in time slots and a change in frequency. It has high reliability even in a plant environment with many metal structures because of the time-division access characteristic and channel hopping characteristic of hopping multiple channels, and it is possible to guarantee a deterministic delay time by providing communication of devices to the divided time slot according to the schedule. In the TSCH network, all nodes are synchronized with respect to time. An area composed of a time slot and a channel is called a cell, and each node exchanges packets through the cell. The set of time slots and transmittable channels is referred to as a slot frame, and the slotted frame repeats continuously while the network is being formed. The absolute slot number is the total number of time slots that have elapsed since the network was formed and shared by all nodes. The frequency used by each node in the network was selected based on the equation corresponding to Equation (2). Nc is the total number of channel offsets. The actual frequency f varies for each slot frame because the absolute slot number ASN increases over time. \[\text{f}=\text{FI}(\text{ASN}+\text{ChannelOffset})\text{ mod Nc}] \tag{2}\]  
In Figure 2, six nodes(Node A-F) form a TSCH network to exchange data. Packets are sent and received by repeating Tx, Rx, and Sleep in a single cell divided into slot offset and channel offset. In a shared cell, control messages to help form or maintain a network are exchanged. Typical examples are enhanced beacon (EB) [16] for configuring a network or DIO for forming a network topology. Packets contained data can be sent and received in a fixed cell. The scheduling scheme that determines when each node sends and receives packets (in what time slot) and which channel is used is not covered by the IEEE 802.15.4e TSCH standard and varies depending on the specific application. The length of one cell in the TSCH standard is 10 ms, which is the time required to transmit a frame and receive the received ACK. In an unused cell, no packet transmission is performed by any node, and each node maintains a sleep state. \begin{table}
\begin{tabular}{c c} \hline \hline
**Proposal** & **Description** \\ \hline Trickle-F [11] & The RPL nodes are prioritized to transmit DIOs to adjust the transmission cycle. \\ \hline Algorithm for Energy-Efficient Node Mobility [12] & \
\begin{tabular}{c} Dynamically adjust the transmission interval of the message according to the speed and direction of travel. As mobile nodes move, fewer messages are required per unit hour to select a new parent node. \\ \end{tabular} \\ \hline EMA-RPL [13] &
\begin{tabular}{c} Neighboring nodes of the moving node predict the movement of the moving node through the RSSI value and select the parent node. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: A summary of routing protocols for mobile node support. The scheduling technique of TSCH wireless networks depends on the application they choose, and many studies are underway [17]. In addition, there is a centralized technique for the root node, which is the core of the network, to manage all schedules as a central scheduler, or a distributed scheduling scheme that is distributed through the process of negotiating cells between each node. In addition, a link-based scheduling scheme is presented, leveraging the MAC addresses between two different nodes.