Research On RPL Routing Protocol For Low Power And Lossy Networks

With the rapid development of Internet of Things technology,the the low power and lossy networks(LLN)which are constructed by various of sensor nodes based on different application requirements have received extensive attention.The LLN has a wide range of applications,such as environment monitoring,health care,industrial control and so on.However,the wireless sensor nodes that make up the LLN are usually limited in processing capabilities,storage space,and energy(battery power).Therefore,the Internet Engineering Task Force has proposed an IPv6-based routing protocol for LLN(RPL)to meet a wider range of application requirements.In this thesis,we mainly study in terms of network congestion control and routing repair and make some improvements based on the summary of existing routing algorithm for LLN.The specific research work made in the above two aspects is as follows:To deal with the problems that the load balancing algorithm in LLN can not reduce the probability of network congestion effectively and the existing network congestion control algorithm can not alleviate the network congestion effectively,a centralized congestion control routing protocol based on multi-metrics combination(CRPMC)is proposed.The protocol comprehensively considers the multi-metrics such as the residual energy,queue utilization,link quality,and the number of sub-nodes to complete the construction of the network topology;Considering the data traffic and the load status of the alternate parent node of its child node by the network congestion node,and adopts a centralized way to replace the current data transmission path of its child node;The “ping-pong effect” problem is solved to network turbulence.Theoretical analysis verifies the effectiveness of CRPMC and the simulation results show that the probability of network congestion,the average network lifetime,and the average throughput of sink nod have been improved.To deal with the problems that the control overhead redundancy,large repair delay and routing loop of routing algorithm for LLN,a high-efficient loop-free based repair routing protocol for LLN(HLR-RPL)is proposed.This algorithm mainly includes three improvement mechanisms:(1)a “cancel the link failure notification message”mechanism is proposed.It uses a modified destination oriented directed acyclicgraph(DODAG)information solicitation message(MDIS)to notify the children and neighbor of link broken node's the link broken status while repairing the routing failure;(2)a “reduction the control message reply” mechanism is proposed.After a neighbor node of the link broken node receives an MDIS control message,it is not always necessary to reply a DODAG information object message(DIO);(3)a “sub-nodes switching of the link broken node” mechanism is proposed,which can make the network topology in an optimal state after the link failure repair.Theoretical analysis verifies the effectiveness of the HLR-RPL algorithm and the simulation results show that the normalized control overhead of the HLR-RPL algorithm is reduced by more than 25%,the delay of the route repair is at least reduced 32.64% and the emergence of routing loop phenomenon can be effectively avoided by comparing with the existing routing repair algorithm.Finally,the work of this thesis is summarized and the further research of RPL routing protocol in LLN is prospected.