| Wireless sensor network (WSN for short) is one of the promising research subjects in the field of information in the 21st century, which contains embedded computing technology, wireless communication technology and sensor technology and so on. It has a very broad application prospect in domains of industrial, agriculture, military, medical and environmental monitoring.By using lots of cheap and miniature sensor nodes which placed in monitoring area, WSN could achieve the purpose of real-time monitoring in the region of interest, by means of sensing various environmental information, all these sent back to user through wireless ways of own multi-hop network. WSN has lots of characteristics, such as low cost, big sampling density, deployment convenient, higher stability, etc. These advantages make it very suitable for farmland environment monitoring applications, supporting the implementation of precision agriculture. This topic is just under the background of the farmland environment monitoring application of WSN.As one of the supported technologies of wireless sensor network, operating system offers software platform for sensor node running, which is mainly responsible for the allocation and callback of all software and hardware resources, coordinates and regulates various kinds of operates, offers the foundation of communication protocol and other application development. Besides, node location information is essential in environmental monitoring application, which can help users make more accurately judgments of events. Measuring and estimating the distance of nodes is the important prerequisite of Range-Based positioning.The two aspects discussed above are the research emphases in this thesis. The main works which have completed in this thesis are as follows:(1)The thesis introduces the network structure of WSN in farmland monitoring application, and designs a kind of software system structure which applicable to the WSN nodes. Then, the thesis completes node software system design using modular design ideas, and further details the design and realization process of the operating system, which mainly includes task scheduling, timer management and power management.These three parts mainly describe their own design thought,main functions, realization process.The experimental results show that the node software system ensures operation stability, by which further research can be achieved.(2) The thesis conducts ranging research based on Link Quality Indicator (LQI for short) that obtained from MC13224, performs various experiments to analysis the characteristics and related factors of LQI, and finds out the relationship between LQI and distance by comparing several curve fitting algorithm. Then, based on the location model, two kinds of ideas are used to complete ranging process: one is the preconditioned of LQI data, including the strategy of selecting values and the procession of revising, another is the follow-up processes, including the error compensation and the distance value correction. In the actual experiment, these ways achieve good effects.Finally, the thesis summaries and analysis the technology of LQI ranging. |
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