Impact of Minimal Cell Allotment on Network Formation and Maintenancein 6TiSCH-based IoT-LLN

Internet of Things-Low Power and Lossy Networks (IoT-LLN) is a technology that allows devices with limited power and bandwidth to communicate, making it ideal for IoT applications. In IoT-LLN, two key protocols are responsible for network formation and maintenance: IPv6 over the IEEE 802.15.4e TSCH mode (6TiSCH) and the Routing Protocol for Low-Power and Lossy Networks (RPL). These protocols exchange many control messages between devices to facilitate prompt network formation and maintenance. The 6TiSCH protocol allows these control messages to be transmitted or received only during the minimal cell. In IoT-LLN, only one minimal cell is allotted for each slot frame. All nodes in the network send their control messages at the minimum cell rate, which becomes overcrowded, leading to message collisions and control message queuing delays. This causes delays in joining new nodes to the network and frequent parent switches in existing nodes. To study this issue, simulations were run using the Contiki-NG COOJA simulator. Simulation results show that, even in scenarios with static nodes, most nodes switch parents often. This reduces network reliability and increases power consumption, a major concern for low-power IoT devices.