Low-cost Low-power Wireless Communication Technology Of Measuring And Controlling System In Greenhouse

Nowadays, cable communication based on 485 bus and CAN bus is adopted widely in measuring and controlling system for greenhouse. But the cable communication manner has several disadvantages such as complex line, difficult maintenance and high cost. It is an effective method for solving the communication problems of greenhouse measuring and controlling system to utilize wireless sensor network to realize data transmission. Hence, the realization of low-cost low-power greenhouse measuring and controlling system based on wireless sensor network is an important task which needs to be solved urgently.To solve the problems of information transmission technology for greenhouse measuring and controlling system, propose systematic physical and logical framework of changing structure ad-hoc wireless sensor network according to practical structural characters in greenhouse. At the same time ascertain key technological parameters of the network including systematical communication frequency, the covered radius of sink nodes and sleeping time of sensor nodes etc, establish a dynamic star frame of wireless sensor network. Synthetically analyzing existing hardware nodes of wireless sensor network, select low-cost low-power components and design hardware circuit composed of wireless communication module, position module, display module and RS-232 serial communication module. Through debugging 2.4G wireless communication module with high-performance spectrum analyzer GSP-830, matching networks circuit parameters are determined which achieves multi-frequency credible communication among nodes. The low-cost wireless communication module, whose protocol including physics layer and MAC layer is too simple, cannot organize complex network by itself. Therefore, it's necessary to design extended frame in order to perfect network protocol through considering IEEE 802.15.4 and selected dynamic star wireless sensor network. Moreover, communication algorithm of the nodes including sensor nodes, control nodes and sink nodes is provided which settles the connection problem among nodes.Research results show that the communication method of dynamic star wireless sensor network which dynamic second-class sub-network is formed during sink nodes move reduces the point-to-point communication distance and saves energy effectively when the number of second-class sub-network in the same first-class increases. Besides the communication energy consumed in system increases less slowly when the length of the rail increases. Hence, the communication method prolongs the period of redeploying batteries in the network.This paper is supported by the national 863 high technology research and development program "Research on greenhouse measuring and controlling system of new-style changing structure ad-hoc wireless sensor networks(serial number: 2006AA10Z258)".