Research On Staggered Transmission Of Large-scale Internet Of Things Based On ZigBee Network

The rapid development of the Internet of Things technology has accelerated the arrival of the Internet of Things era.ZigBee,which based on IEEE 802.15.4 is widely used in smart home,smart agriculture,smart medical and other fields due to its unique network characteristics such as short distance,low power consumption,and low speed.However,in practical applications,due to the design of the protocol,the formation and communication of the ZigBee network can only be carried out on a single channel,which results in the data transmission during large-scale network deployment being limited by the channel environment.Therefore,it is necessary to study the corresponding strategy to solve the data transmission problem in the actual use of ZigBee network.In this thesis,in the actual data transmission process of a large-scale Zigbee sensor network,the problem of invalid backoff in the early stage of channel access,the unfair problem of short-term access of nodes and the delay of heterogeneous data transmission are conducted in-depth research.Combining the data transmission process of the ZigBee network protocol and the specifications of the MAC layer protocol,the competition period channel access control algorithm strategy and the non-competition period peak time slot allocation strategy are designed.While ensuring the reliable transmission of the entire network data,the delay is based on heterogeneous data.The demand for delay is reduced,thereby reducing the energy consumption of the node during data transmission and extending its service life.So that the improved network can meet more needs in the actual applications of ZigBee network.The main research work of this thesis is as follows:(1)Aiming at the transmission problem of the time slot request frame during the superframe contention access period,the standard backoff algorithm is improved,and the fixed backoff index and the successively decreasing backoff period are used to satisfy the short-term access fairness of different time slot request frames.Reduce the early invalid backoff time,model the improved algorithm with Markov chain,analyze the performance index of the algorithm under this model,and find the most suitable backoff index under the condition of meeting the maximum node receiving rate.(2)In response to the problem of heterogeneous data transmission during the contention-free period in the actual scenario,a peak-shifting time slot allocation strategy is proposed.The application layer of the terminal node completes the division based on the relative transmission period and the data type in emergency situations,and designs the corresponding data in the MAC layer.The time slot request frame is used to identify the delay requirements of heterogeneous data.At the coordinator side,an improved knapsack algorithm is used to complete the allocation of guaranteed time slots during the non-contention period.While ensuring the maximum transmission value,it can satisfy more time slot requests and improve the performance of the entire network.(3)According to the data transmission strategy proposed in this thesis,the simulation analysis of the network simulation level is carried out,and it is compared with the algorithm of the protocol standard and the algorithm of the existing research.Analyze the transmission performance and feasibility of the scheme from the perspectives of heterogeneous data transmission delay,node throughput,energy consumption and maximum transmission value,and show the feasibility of the scheme.