# Efficient Route Management Method for Mobile Nodes in 6 TiSCH Network
###### Abstract  
The combination of time slotted access and channel hopping technology in IEEE 802.15 TSCH networks enables high reliability and low power operation to meet the stability and real-time requirements of industrial applications. Basically, TSCH and RPL, a routing protocol for TSCH, are proposed for static nodes that generate fewer control messages, so they allow collisions in shared cells when they exchange control messages. In a topology containing mobile nodes, the collision of control messages in a shared cell makes the network difficult to recover quickly. The proposed scheme minimizes the collision of control messages by allocating dedicated control cells to form preferred parent nodes quickly for mobile nodes. We also proposed a method for establishing a fixed route from the root node to the mobile node in RPL to minimize the delay time. Through the simulation using the 6 TiSCH simulator, it was confirmed that the performance of the proposed method was approximately 2.5 times better in terms of overhead and resource use, and 33% better in terms of network participation time of mobile nodes compared with existing solutions. time slotted channel hopping; mobility; RPL; scheduling +
Footnote †: journal: Physics Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. proposed the IEEE 802.15.4e time slotted channel hopping (TSCH) [4] standard. The TSCH network resolves collisions or contentions that may occur during wireless communication through medium access control technology that divides time into time slots. In addition, through the channel-hopping technique, a multipath fading problem can be solved by preventing collisions because of an increase in time slots and a change in frequency. There are several scheduling techniques that determine when each node sends and receives packets on a TSCH network (at a certain time slot) and through which channel, but research on a scheduling technique to support mobility has not been actively conducted. The node that wants to participate in the network initiates the DODAG Information Object (DIO) message cycle by transmitting the DODAG Information Solicitation (DIS) message. The node receiving the DIS message transmits the DIO message, and the node receiving the DIO message starts the network formation. As the mobile node moves, the mobile node disconnects from the existing parent node and transmits a DIS message through the shared cell to participate in the network, and the node receiving the DIS message transmits a DIO message through the shared cell. In the process of forming a routing path in the Routing Protocol for Low-Power and Lossy Networks (RPL) protocol, both DIS and DIO messages are transmitted and received in a shared cell, and the cell operates on a contention basis. The more nodes that have received the DIS message, the more nodes that send DIO messages, causing more collisions and data loss of control messages in the corresponding shared cell. Therefore, there is a need for a technique that supports mobility by reducing the collision of control messages in a shared cell. In contrast to the existing scheduling scheme, the proposed scheme allocates a dedicated cell for the control packet to prevent collisions that may occur during the exchange of RPL control packets, thus, reducing the handover delay time and control overhead of the mobile node. In addition, it is necessary to minimize the dropout of packets generated by the mobile node when the communication link with the existing parent node is temporarily released owing to the movement of the mobile node. Therefore, we propose a scheduling scheme that immediately responds to a change in the link quality of a mobile node, delivers a control packet to a neighboring node, quickly selects an alternate parent node, supplements a path, and minimizes the omission of transmitted packets.