Research On Congestion Control Protocol In Wireless Sensor Network

With the rapid development of wireless sensor networks,it is more convenient to collect data.However,the arrival of the era of big data makes the data in wireless sensor networks increase dramatically.When the amount of data to be processed in the network exceeds the limit processing capacity of the network,the network will be congested.Network congestion will bring various kinds of network problems,such as packet loss,increase of network delay,decrease of throughput,and excessive consumption of energy.Congestion control protocol is a series of measures to improve network performance after congestion.Although congestion control protocol can alleviate the congestion and improve the performance of the network,there are still some difficulties.Wireless sensor network is formed by a large number of sensor nodes self-organization,in which there are not only node congestion caused by buffer queue overflow,but also channel congestion caused by mutual interference between links.Therefore,how to solve these two kinds of congestion to improve the data transmission environment,improve network performance and optimize the use of network resources is the research goal of this paper.In order to solve node congestion,this paper proposes a hop-by-hop bidirectional congestion control(HBCC)algorithm based on contention MAC protocol.After in-depth study,it is found that the existing hop by hop congestion control algorithm is unidirectional,and there are problems of effectiveness and limitations.HBCC algorithm proposes bidirectional congestion control,which not only considers the current congestion situation of the node,but also combines the congestion situation of the previous hop node and the next hop node.The algorithm takes the queue length as the parameter of congestion detection.By detecting the queue length of the current node and the next hop node,congestion can be divided into four categories: 0-0,0-1,1-0,1-1(0 indicates no congestion,1 indicates congestion).In view of these four congestion conditions,HBCC algorithm sets new congestion mitigation strategies: HRCC(Hop-By-Hop Receiving-Based Congestion Control)?HSCC(Hop-By-Hop Sending-Based Congestion Control)and HPCC(Hop-By-Hop Priority-Based Congestion Control).The contention window of the current node is adjusted according to the congestion degree,that is,the priority of access channel of current node is changed,so that the length of the buffer queue of node is reduced.The simulation results of NS2 show that HBCC algorithm has advantages in reducing the length of buffer queue,alleviating node congestion and improving network performance.In order to solve the channel congestion,based on the backoff mechanism,this paper proposes a network scale adaptive slot utilization competition control algorithm UCC(utilization content control).By studying and analyzing the binary exponential backoff mechanism of IEEE 802.11 protocol,it is found that the data transmission opportunity is in a state of two-level differentiation,and the network competition is not considered when the nodes are collision backoff.These problems of binary exponential backoff mechanism can easily make the nodes of different links collide when transmitting data in the channel,which will cause link interference and channel congestion.In order to solve the shortage of binary exponential backoff mechanism in IEEE 802.1 protocol,this paper proposes a slot utilization competition control algorithm UCC which can adapt to different network sizes.Before adjusting the contention window,the algorithm calculates the contention level of the network according to the detected channel conditions,Then,the contention window of the next access channel is set according to the contention level.NS2 simulation results show that the UCC mechanism not only improves network throughput,but also balances collision and delay.UCC makes full use of channel resources,reduces the collision of nodes in the channel,alleviates channel congestion and improves network performance.