Research On Conflict Problem Of IEEE 802.15.4-based Multi-hop Wireless Sensor Networks

IEEE 802.15.4-based multi-hop wireless sensor networks are widely used in military,environmental monitoring and forecasting,building structure health monitoring,and so on,because of its self-organization,low cost,low power consumption and easy deployment.However,the conflict problem in the multi-hop wireless sensor networks greatly affects the performance of the network,such as throughput,delay and energy consumption.Therefore,this paper deeply studies the conflict problem in the multi-hop wireless sensor network.In this thesis,we focus on the conflict problem in multi-hop wireless sensor networks.Firstly,we study the topology design of the network with the presence of hidden terminals.By analyzing the hidden-terminal-pair ratio in multi-hop wireless sensor networks where nodes are randomly deploy,we propose a node deployment strategy which can minimize the conflict problem while ensuring network connectivity.Secondly,we analyze the error characteristics of conflict packets caused by different reasons at bit-level and symbol-level.We extract error characteristics of the continuous conflict packet caused by hidden terminals based on experimental methods.As is shown in our analysis results,continuous collisionpackets caused by hidden terminal present markedly different characteristics from other scenes in terms of the bit error rate,the distribution of error bit position,the continuous error bits and symbols,and so on.Thirdly,with the incorpaoration of the error characteristic of conflict packets,we propose conflict recognition mechanism based on generating domain.We design the overall frame of the mechanism and perform comprehensive analysis,comparisons and researches on the parameters of the generated domain.Based on the bit error rate of the generated domain in received error packets,the mechanism allows receivers to recognize the reason of failed transmission.The feasibility snalysis results show that the reliability of the mechanism can be over 80%.The node deployment strategy for IEEE 802.15.4-based multi-hop wireless sensor networks and the conflict recognition mechanism based on the generation domain provide a new method to improve the transmission performance of multi-hop wireless sensor networks.