Farmland Information Retrieval System, Wireless Communication Design And Implementation And Ranging

As the prospects of the current agricultural development, precision agriculture combines the agricultural production and the information technology, and takes full advantages of information technology to improve the existing mode of the agricultural production and increase the agricultural outputs. Collecting the environmental parameters of the field crops' growth process is the basis of implementing precision agriculture, which provides necessary and reliable data for making proper strategic decisions for planting. This subject designs wireless sensor network (WSN) ground monitoring sub-system and implements it, which is supported by the project of cooperative retrieval system for field information combine the means of ground monitoring and satellite remote sensing to forming retrieval model in CNGI. Meanwhile the experiments for ranging measurement based on this platform are completed.This thesis analyzes the current research process of precision agriculture, and summarizes main applied technology - WSN and GPRS. Then, it presents the structure of the whole project, points out the important position of the monitoring system in the project, and introduces the software design and hardware components in details. After that, as an important part of this paper, wireless communication of the system is presented. Wireless communication consists of long-distance communication based on GSM/GPRS and short-distance communication based on Zigbee. Short-distance nodes complete short-distance communication, while long-distance nodes complete both of them at the same time. Hence, long-distance nodes modify the application layer of the Zigbee protocol stack, and add referred events and tasks to application layer. Moreover, it focuses on the realization process of long-distance communication by using AT command set provided by SIM300C module.Furthermore, as one of the important part of this thesis, data collection mode of this system, including the design for the data collection, the control commands, and the error information, is proposed. Also, the data upload format and storage format is presented. The data from nodes in the monitoring center is shown in this paper. As the first step for localization, ranging experiment is an important component of this article. A new method - LQI value is used to calculate the distance of nodes in this experiment based on our platform. Comparing to RSSI, the relationship between LQI and the distance is uncertain, so, further research is needed. We have did a large number of experiments to find out the relationship between LQI and distance, proposed many environmental factors affected LQI, and presented a fitting curve of LQI and distance. The experiments results show that the simple LQI ranging results are not satisfied. Then, in the further research for this subject, the corresponding algorithm should be proposed for amending the distance coming from LQI value, to achieve more precise positioning.