Design Of Adaptive Transmitting Power For Low-power-consumption WSN In Rice Fields

Wireless sensor network,WSN,relying on its own advantages,can realize information’s remote perception and transmission by deploying a large number of low cost wireless sensor nodes which can work together through ad hoc network.By equipping the specific sensor on the node,the wireless sensor network can widely use in the field of smart home,military,wisdom agriculture and health service.Wireless sensor network applied to the agricultural information collection,can promote the informatization and intellectualization of agricultural production.There are lots of researches which are based on the wireless sensor network home and aboard,especially the precision agriculture based on collection of crop information,have been widely applied.In the research of wireless sensor network,adaptive transmitting power is the key difficulty.With the background of wireless sensor network applied to the rice filed environment monitoring,this paper analyzed the research situation on the adaptive transmitting power and routing algorithm home and aboard.To solve the problems occurring in surveying the farmland environment such as the limited energy and the different distances of communication among the nodes,a monitoring system with adaptive transmitting power for rice fields based on RSSI(Received Signal Strength Indication)and PLR(Packet Loss Rate)was designed and a long-time,stable and highly reliable WSN(Wireless Sensor Network)running this algorithm with low power consumption was established.In the aspect of hardware,the node uses a STM32F103VET6 as a processing core.The wireless communication module is made of E41-T10S2 chip and its peripheral circuits.The hardware circuit also includes many modules such as power module,USART debug module,received signal strength reading module and peripherals power management module.Besides,to extend the network coverage and improve the stability of the system,the method of the frequency heterogeneity was adopted to cluster the nodes and to configure different antennas for different nodes.In the aspect of software,the mini embedded FreeRTOS(Free Real-time Operating System)was selected to improve the utilization of CPU and prolong the working life of the clusters.Additionally,to reduce the power consumption,the mode of timed sleeping and waking as well as the power-down control of sensor were selected as the working pattern and the adaptive low-power-consumption mechanism were used on the basis of data deviation perception.The result of tests showed that the system can adaptively adjust the transmitting power to the minimum value that can meet the demand of the stability of communication(PLR was less than 1.3%)within the communication distance of 150 m according to the quality of current communication.In this situation,when the algorithms of adaptive transmitting power adjust to 8dBm,6dBm,and 3dBm respectively from 10 dBm,the battery duration of nodes increased by 11.9%,21.4% and 33.3%.As the result revealed,the communication performance of the nodes in this paper is significantly better than three other nodes with different adaptive transmission power algorithms.As it can be seen,the system is highly stable and practical in the application of WSN for the monitoring of the farmland environment.Using wireless sensor network into the rice field environment monitoring,meets the requirement of the informatization and intellectualization of agricultural production,which can release the work of monitoring workers and has good actual benefit.