# Efficient Route Management Method for Mobile Nodes in 6 TiSCH Network
## 3 Efficient Route Management Method for Mobile Nodes in 6 TiSCH Network
### Fast Parent Selection Technique for Mobile Nodes  
A technique for generating packets from a moving node to a preferred parent node and forwarding them to the root node has been proposed, but the movement of a moving node often leads to link disconnection from an existing preferred parent node, resulting in packet transmission. If the communication link with the preferred parent node is released, missing packets can have a significant impact on applications that continuously collect data. Therefore, when a moving node recognizes that its link to its preferred parent node is disconnected, it informs the neighboring node that it wants to participate in the topology, receives a DIO message without conflict, and recovers the link quickly. This technique was performed after the move-root node fixed-path construction technique. While propagating to neighboring nodes in the previously proposed move-to-root node fixed-path, it also delivers the MAC address of the move-to node. At this point, we assign a Tx cell dedicated to unicast control by determining the slot and channel offsets using the agreed hash values of the moving node's own MAC address and the MAC address of the moving node. The assigned cells remain in a normal sleep state, and when a moving node broadcasts a shared cell with a DIS message stating that it is disconnected from its preferred parent and that it needs to configure a new topology, it sends a unicast DIO message to the moving node. In addition, moving nodes receive DIO messages containing their own MAC addresses propagated by neighboring nodes while maintaining their topology. When a moving node receives a DIO message, it uses the neighboring node and its MAC address to determine the slot and channel offset to assign an Rx cell dedicated to unicast control. Conflicts between neighboring nodes do not occur because they know each other's MAC addresses and assign cells dedicated to unicast control based on their MAC address hash values. The cell neighboring node F of the preferred parent node of the current moving node allocates a control-only Tx cell directed at the moving node based on the MAC address with (slot offset, channel offset) = (2, 3). Mobile nodes also allocate control-only Rx cells from neighboring nodes in cells (slot offset, channel offset) = (2, 3). It still communicates with the preferred node; therefore, it assigns a control-only cell, but the radio is off, and hence, packet switching is not performed in that cell. When a moving node detects a link release from its preferred parent node owing to the movement of a moving node, the moving node broadcasts a DIS message from a shared cell and turns on the control-only cell Rx radio of the moving node. From the following slot frame, a neighboring node can receive unicast control messages from that cell. The neighboring node has an Rx radio turned on in the shared cell and receives DIS messages from the moving node. When a shared cell of a neighboring node detects that it is a DIS message from a moving node, it immediately sends a unicast control message to the moving node from a Tx cell dedicated to unicast control. On a moving node, the radio is turned on in a control-only Rx cell on a neighboring node and unicast control messages are received. The purpose of the technique is to receive DIO messages without conflicts and quickly recover links; therefore, if any of the control-only Rx cells are received, while the radio is off in the control-only Rx cells in the slot offset, they no longer receive unicast control messages from other neighboring nodes. Figure 5 shows a simplified schedule of mobile nodes in the network shown in Figure 6. The topology shown in Figure 6 is a situation in which the movement of a mobile node releases a link assignment with node E and changes to a preferred parent node with node F. For example, in the first slot frame, in slot frame 7 of mobile node M, there are Rx cells dedicated to control with node D and Tx cells dedicated to data with node E that send and receive data packets.