Internet of Things (IoT) refers the technology for connecting resource constrained devices around us to the Internet via wireless networks. Through the application of IP technology to communications between devices, IoT is expanding its application area to a wide range of applications in various environments. Communication reliability in IoT networks is an important factor for reliable low-power data transmission. Through the guarantee of communication reliability in the IoT network, the application field of IoT can be expanded to various fields such as the emergency service, beyond the application field of the existing wireless sensor network.
In order to improve the reliability of data communication in the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) based IoT, a different approach is needed depending on the characteristics of the data flow. For the data collection, we focus on TSCH with RPL. We research the timeslot scheduling algorithm for TSCH using routing path of RPL to achieve the goal of ensuring the reliable data and the low end-to-end delay. In addition, RPL provides two optional modes for downward routing, these two modes have advantages and disadvantages that conflict with each other, and the disadvantages of these two modes are weak points when consisting large-scale networks. Therefore, in order to improve the reliability of data communication, the downward routing of RPL needs to be improved.
In this dissertation, we propose novel algorithms to improve communication reliability considering characteristics of data communication flow in RPL-based IoT networks. Firstly, we propose a scheduling scheme, named Escalator, optimized for the data collection based on the routing topology generated by RPL in a TSCH based network. Escalator provides a slotframe schedule for a network in which all nodes can send packets to the sink in every slotframe cycle, regardless of the network topology.
Secondly, we propose a hybrid downward routing mode to improve the reliability of downward packet transmission in RPL based networks. The proposed hybrid mode stores a routing information by distributing the information to a DODAG root and routers. Then, the proposed hybrid mode provided a solution for the scalability issue occurred from resource limitation of routers in the storing mode as well as the increase in the fragmentation stemming from routing overheads in the non-storing mode.
We implement the proposed algorithms and evaluate their performance with existing schemes through a testbed and simulation. The experimental results show that the proposed algorithms have lower end-to-end delay and higher packet delivery ratio compared to the existing schemes. We also discuss future works.