Research On Structure Of Wireless Sensor Network Of Monitoring System In Greenhouse Based On Virtual MIMO

Wireless sensor network (WSN) is intelligent network system that consists of a large number of small sensor nodes which can communicate, compute, and operate independently according to the environment. WSN provide strong technical support for monitoring system in greenhouse, because it's low cost and convenient application. However, the small size of sensor nodes limits their energy capability, and battery can not be replaced frequently, so the energy issue has become the strongest challenge of the wireless monitoring system in greenhouse. Therefore, the primary goal of designing wireless greenhouse control system is the energy efficiency of sensor nodes and prolonging the lifetime of sensor networks.By analyzing the key factors that affect the energy consumption and the existing energy saving technology, we propose virtual multiple-input-multiple-output (MIMO) clustering algorithm which applies to small and medium scale wireless network of monitoring system in greenhouse. We introduce energy-efficient virtual MIMO communications technology based on dynamic power management, and select cluster head randomly and circularly to balance networks energy load and prolong the lifetime of WSN. We use low power microcontroller MSP430F135 and the wireless radio transceiver chip CC2420 which support IEEE802.15.4 protocol to build energy test platform of sensor network control system in greenhouse. We do experimental research on the relation between transmitting power and the RSSI to solve the path loss factor in greenhouse on the experimental platform, and then the energy model of virtual MIMO clustering network is created. We analyzed the virtual MIMO WSN energy performance influenced by network size, node density and path loss factor, and the longest lifetime of network, and then optimize the proportion of cluster head that the key parameters affect the WSN performance by genetic algorithm to get the longest lifetime of network. The results show that the virtual MIMO clustering algorithm outperforms the LEACH algorithm in energy saving and network lifetime. When the network parameters are appropriate, the lifetime of virtual MIMO network could increase several times.