Congestion Control Investigation For Time Slotted Channel Hopping And Tree Based Industrial Sensor Networks

Nowadays,the large-scale wireless sensor networks(WSN)have been widely used in kinds of industrial Io T business,which consist of many sensors with wireless communication abilities.One popular kind of WSNs is a tree-based multi-hop wireless mesh network,which complies with IEEE802.15.4g and P1901.2 protocols.This WSN makes use of Time Slotted Channel Hopping(TSCH)technology to against radio interference and get more efficient bandwidth utilization.Routing Protocol of Low-power and Lossy Networks(RPL)is designed for this kind of WSN,which defines device just know how to connect with its parents rather than the detailed routing information in non-storing mode based on constrained memory resource.Therefore,for upward traffic,the source device just could send packets to its parent node,and then the parent node forwards to grandfather node.Finally,these packets could be received by border router with such hop-by-hop communication.Besides,for downward traffic,the border router will inject source routing header into IPv6 packet,so that every forwarding node enroute could know how to distribute packet until it is received by destination node.Based on that,in such convergent network,the hot devices laid on key path are used frequently for forwarding packets,which is easy to lead WSN congestion.If hop device gets trapped in congestion,its cached traffic will flood to neighbor nodes,which expands affected area of WSN,reduce the network performance and reduce the maximum throughput.So,how to control congestion is the one of most important subjects in WSN investigations.Most of the traditional congestion control algorithms of WSNs are all about reducing the sending rate of packets hop-by-hop,but due to limited memory resource for device of WSNs in practice,there are not enough buffer to store forwarding packets.Consequently,lots of packets will be dropped en-route,which generates many retransmissions,the network congestion becomes worse than before.Otherwise,another reason of congestion is that the channel access competitions are too strong among neighbors,but the traditional methods do not cover this problem.So,in order to fix out the mentioned problems,this thesis proposes a novel congestion control algorithm of TSCH based WSN,which is called FRCCP algorithm.The FRCCP algorithm proposes a novel method to measure the degree of congestion,and then find out the congestion reason with calculated congestion factor with this method.If the congestion is made by strong channel access competitions,this thesis proposes to use Channel Monopoly Protocol(CMP)– a new channel access method proposed in this thesis – to fix out this problem.Besides,if the congestion reason is due to insufficient memory,this thesis proposes to use a novel method called Multi-Routing Load Balance Algorithm(MRLBA),which could help device to distribute right portion of traffic to the forwarding nodes respectively.At first,MRLBA uses Fibonacci Fan Map to predict the traffic window for parent nodes,and then leverages the special features of multiple parents in RPL-based WSN to distribute buffered packets for different parent device.At last,the hot device of WSN could make good load balance again with MRLBA.In addition,because the traffic is distributed with multiple routing path,the hot device could have stable link quality with existing parent nodes,which avoids the Pendulum Effect problem.The author conducts theoretical analysis of all proposed control algorithms.A prototype of TSCH and Tree-based WSN has been implemented with the proposed control algorithms.Through experiments based on the prototype network we show that our FRCCP algorithm reduces network congestions.In addition,it improves load balancing,and produces higher network throughput as well.