Research On Wireless Sensor Networks Congestion Control Based On IEEE 802.15.4

Wireless sensor networks are widely used in various fields,and the congestion in WSN influences the QoS of the network even makes the network paralysis.Considering the node computing power and energy is limited and many-to-one transmission,congestion control mechanism design in WSN is now becoming one of the most difficult topics for researchers.Congestion control research has made some achievements but not perfect,most of them are based on simple congestion detection and rate adjustment,not combined with the channel access mechanism to expand relieving congestion.This thesis made an in-depth study on child node congestion under sparse event and network congestion problems under intensive event based on IEEE 802.15.4 star sensor networks,a new congestion control mechanisms was proposed and a simulation was made to verify the correctness.Congestion detection used the combination of node-based buffer queue length and the current trends.The test results were divided into three levels and this method made a more accurate result.This thesis built a Markov Model to analyze CSMA/CA mechanism in IEEE802.15.4MAC layer and a method named 'node Adaptive Priority methods to relieve congestion' was proposed based on channel contention access mechanism when the sum of child nodes reporting rate is less than sink node processing capacity.Node adjusted the priority of transmit dynamically according to the degree of congestion.The method cost less and relieved congestion efficiently.On the other hand,a method named'Business priorities and rate adjustments based congestion control' was proposed.This method relieved congestion effectively and ensured the reliable data transmission of higher priority node.Finally,Matlab was used to simulate the proposed congestion control mechanism.Simulation results showed that the algorithm can relieve network congestion and improve the network performance.