Research On Multicast Routing Algorithms Among Low-power Nodes In Internet Of Things

The Internet of things (IoT) builds a ubiquitous network interconnection of all things, of which the node energy, storage spaces, network bandwidths are far less than traditional networks, and links have a characteristic of instability. A large amount of work on IoT routing has been dedicated to the study of effective use of resources to enable effective and reliable data transmission in a dynamic network environment. Compared to unicast and broadcast, multicast communication with higher data transmission efficiency can save network bandwidths as well as node energy consumption during RF transmission, and therefore multicast technology has important applications in IoT.Currently, research studies on IoT multicast span mainly two aspects. One aspect is to lightweight traditional IP multicast routing protocol, establish a multicast routing table for each node on the multicast path, and maintain the multicast topology with low overheads. Another aspect is to design a stateless geographic multicast strategy based on geographic unicast routing, in which nodes realize multicast forwarding through dynamic neighborhood selection algorithm in the support of positioning technology. Both two of the ideas can be adapted to IoT’s characteristics of resource-constrained and network instability. In this thesis, we fist give a thorough review to the literature on these two aspects, and then propose new routing algorithms to improve the performance of existing studies. The main contribution of this paper is as follows:1. For IP-based low-power lossy network routing protocol RPL (IPv6Routing Protocol for LLN), existing algorithms transmit a large number of redundant data, and waste limited node energy resources. This thesis presents an energy efficient RPL multicast routing algorithm, adding available children sets and forwarding nodes sets in all the forwarding nodes while establishing multicast states. The available children sets retain diverse neighbor selecting options to adapt to link feature of LLN, while the forwarding nodes sets retain several group of neighbors with minimum numbers which cover all the multicast receiving nodes. The algorithm selects forwarding neighbors from the forwarding nodes sets, and tries to reduce the total number of forwarding nodes and network energy consumption. Simulation results show that the new algorithm uses less average forwarding nodes during each multicast delivery, and consumes less total energy during its lifetime.2. Geographical multicast routing in Wireless sensor network has a disadvantage of poor scalability. Although some studies use hierarchical network structures to enhance the scalability of geographic multicast, they reduce the lifetime of routing instead. This thesis presents a segmented multicast routing algorithm which is suitable for large-scale wireless sensor networks. The algorithm divides the multicast tree into multiple multicast sub-trees, and storage the location information of segmented destinations. Multicast packets obtain local routing information from these root storage nodes, and proceed with stateless geographic forwarding inside each sub-tree. For root storage nodes, the algorithm also proposed an update scheme, in which storage nodes select alternative nodes to complete storage capabilities when they have insufficient residual energy. Simulation results show that the algorithm can acquire good performance on both scalability and lifetime, and when the size of multicast sub-trees lies in an optimal value range, the comprehensive performance of routing scalability and lifetime can obtain the maximized promotion.