| Agriculture is the basic industry of the national economy. Precision agriculture is the inevitable trend of modern agriculture development, the effective implementation of which is of great significance to level up the agriculture modernization of our country. Wireless sensor network (WSN) is currently one of the main technical means of field information acquisition in precision agriculture implementation. Research on the key technology on WSN applied in presicion agriculture (PA WSN) is of great weight. This dissertation focuses on the energy-efficient technology in PA WSN and carries out research around network structure, communication protocols design, methods for online data aggregation and power saving sampling schule. At the end of the paper, realization of two typical application systems of precision agriculuture is elaborated. The main research work and conclusions are as follows:(1) From the application environment, sampling, data requirements, the deployment of sensors, network structure, network fault tolerance and real-time requirements, particularity and character of PA WSN is analazed, requirements of it are brought up and model of it is defined. Design of PA WSN structure, including service structure, concrete structure and topology is illusturated.(2) Realization of low power consumption network communication protocols for layered, heterogeneous wireless sensor network system is analazed. MAC layer communication protocols are analyzed and source of high power consumption procession is focused. The character of S-MAC is described and its shortcomings in PA WSN are put forward. A load traffic adaptive protocol, called AS-MAC, is designed and elaborated. Considering of the distribution scale and energy difference among the sensor nodes, a new routing protocols called EA-LEACH, is designed which could adjust its data forward path and cluster head slection on basis of the node left energy. At last, the complete communication protocols are introduced, which is mainly composed of AS-MAC, EA-LEACH and Zigbee.(3) From the view of data compression and aggregation in wireless sensor network, how to reduce the overall energy consumption is studied. A data compression method with piece-wise linear regression for PA WSN is designed, which is suitable for periodical data transform. Taking environment temperature, relative air humidity and soil temperature data set as research objects, the compression and data recovery efficiency of the algorithm are tested. Results show that data compression ratio is as high as51.9%when the RMSE between restored data and raw data are3.87%and0.49℃. A data aggregation method on basis of sensor node quadtree coding is put forward. Taking environment temperature, relative air humidity and soil temperature as research object, we tested the effectiveness of the algorithm. Results show that data compression ratio of environment temperature, air relative humidity, soil temperature and soil moisture is11.7%,19.5%,12.64%and33.34%respecitvly.(4) Power saving technology is analyzed in the perspective of sampling schedule.Main realization methods for sampling schedule are reviwed and sampling power comsumption is computed by build power comsumption model of sampling, data process and radio frequency tranceiver. Based on the model definition of sampling schedule, autoregressive prediction sampling scheduling and virtual cluster sampling scheduling is designed. The effectiveness of the two models is evaluated. Results show that sample frequence of temperature and soil huimidity could reduce as high as30%and80%, power consumption could to79.8%with compare of continuous sampling.(5) Two typical PA WSN application systems, group greenhouse monitoring wireless sensor network system and aerial spray deposition measument wireless sensor network system are elaborated in datails including its structure, node design and system character. |
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