Mobility Management Protocols for Low power and Lossy Networks

Abstract

The Internet of Things (IoT) is emerging as a new paradigm for information systems as things are seamlessly integrated with computation and communication capabilities. The Wireless Sensor Network (WSN) is a key component of the IoT environment which is typically composed of large-scale resource-constrained devices, that exploit the Multi-Hop data delivery over wireless links. Recently, the Internet Protocol (IP) based WSN has gained popularity due to the many opportunities it provides for direct communication with the WSN as well as remote access to the sensor data. On the other hand, assigning IP for sensor devices raises numerous challenges due to its resource constraints. Nevertheless, the Internet Engineering Task Force has developed the IPv6 over low power wireless personal area network (6LoWPAN) adaptation layer that enables IPv6 communication over the IEEE 802.15.4 layer, and also standardized the IPv6 Routing Protocol for Low power and Lossy Networks (RPL), to route packets over the 6LoWPAN adaptation layer. The RPL is a gradient-based routing protocol with bidirectional links that aim to build a robust Multi-Hop mesh topology based on the routing metrics and constraints. However, several issues remain open for improvement and specification, in particular with respect to node mobility that arises in real-time scenarios. Several examinations have illustrated that the RPL is affected under mobility. There are various solutions proposed in the literature to support mobility in the RPL, with limitations. In order to address these issues, this thesis aims to support mobility in the RPL with enhanced performance. The effects of mobility in the RPL is evaluated with different Objective Functions (OFs) such as Objective Function Zero, Energy-based Objective Function, Delay-Efficient Objective Function, and Minimum Rank with Hysteresis Objective Function under different mobility models. Subsequently, it proposes a Multimetrics based OF (MMOF) based on the node type by considering node properties as well as the link properties. It proposes new mechanisms to update the Preferred Parent Node (PPN) based on the control messages to maintain connectivity to the DODAG root. Further, various timers modules are incorporated into the proposed techniques in order to maintain up to date neighbour nodes. To evaluate the efficacy of the proposed protocols, simulations were carried out by using Contiki based Cooja simulator by varying system and traffic parameters. The simulations were repeated for 3 times and average of the results were considered for evaluating the performance. Different evaluation metrics, namely, the Packet Delivery Ratio (PDR), power consumption, end-to-end delay, and the number of control messages were considered to evaluate the performance of the proposed protocols. Based on the obtained experimental results, it was observed that under mobility, the OFs have a direct effect on the evaluation metrics. The proposed MMOF along with a mechanism to update the PPN showed improved performance in terms of PDR and power consumption compared to other protocols