Section IV describes the approach of energy-efficient organization, including sensor node awakening and dynamic routing scheme. Experimental results are provided by Section V. Finally, Section VI presents the conclusions of the paper.2.?PreliminariesThe two-dimension sensing field is filled with randomly deployed sensor nodes. Their positions are provided by a global positioning system (GPS). A sink node is located in the centre of the sensing field. Sensor nodes sense collaboratively within a specified sensing period [8]. As the historical target positions become available, the sink node can forecast the target position of the next sensing period.2.1. Multi-Sensor ModelIt is assumed that each sensor node equips two kinds of sensors, one pyroelectric infra-red (PIR) sensor and one omni-microphone sensor.
Sensor nodes obtain the bearing observations with the PIR sensors, while the range observations are produced by the omni-microphone sensors. For each sensor node, it is assumed that the two sensors have the same sensing range Rs. The coordinates of the sensor node and target are denoted by (xis,yis) and (xtarget, ytarget) respectively. Then the true bearing angle is calculated as:��it=arctanytarget?yisxtarget?xis(1)and the true range value is calculated as:rit=(xtarget?xis)2+(ytarget?yis)2(2)Both sensors have zero-mean and Gaussian error distribution. The standard deviation of bearing and range observations is �Ҧ� and ��r respectively.
The observations produced by the sensor node i are:��i=��it+w��(3)ri=rit+wr(4)where wb and wr are the corresponding Gaussian white noise.
2.2. Energy ModelFor Batimastat the scalability of energy consumption in WSN, all the components of the sensor node are supposed to be controlled by an operation system, such as micro Operating System (��OS) [1]. Thereby, shutting down or turning on any component is enabled by device drivers in the specified WSN application.During sensor node operation, four main parts of energy consumption source are considered: processing, sensing, reception and transmission. The processing energy is spent by the processor with memory. It is assumed that when the processor is active it has constant power consumption. The embedded sensors and A/D converter are adopted as there is any sensing task, and the corresponding power consumption is a constant.
For wireless communication, the reception and transmission energy is derived from the RF circuits.When the reception portion is turned on, the sensor node keeps listening to the wireless Drug_discovery channel or receiving data. For the transmission portion of RF circuits, the transmission amplifier has to achieve an acceptable magnification.