【正文】 ys ―Power Down‖ sleep mode of the microcontroller for the time the node is inactive, thereby saving substantial amount of energy. Another option could be to use a dual clock scheme instead of sleep mode, but while using an external Real Timer Clock, we are able to save the required power in our ―Power Down‖ sleep mode itself. The Power Down mode features putting everything to a plete shutdown, including the clock source [7] and typically consumes less than 10uA of current with ―Watchdog‖ enabled at . Brownout detector remains the only analog module in terms of power consumption during a sleep mode state [18]. But since even this module is not required in our design we have turned it permanently off ensuring further lower powered “ Power Down‖ sleep mode. Another power saving mode, the “ Power Save‖ sleep mode is employed when smaller delays are required between processing and reading sensors. Along with microcontroller other peripheral are also put to sleep mode to minimize energy usage. The GPS is switched off while the node is in sleep mode. This is implemented by the use of power switch, TPS2092 [19]. The application being not very time critical gives us the opportunity to put the radio transceiver in lowest power mode which consume about 5 times less power than the other modes. C. Node lifetime estimation Table 1 explains the power requirement of various ponents of the node. The following assumptions have been taken in estimating the energy requirements of the node for it to survive minimum of one year: ? The node takes measurements every 3 hrs. ? It is assumed that most of the time, the Barasingha, would be under open skies, getting a clear GPS lock. ? The node tries to discover other nodes/base every hour, synchronized by the RTC. ? Only 70 percent of the total rated Liion battery energy has been assumed usable [20]. ? Lastly, we assume that a node per day will receive a maximum of 7 pages from its peers and transfer one page to the other. In a month’s time the node will transfer all its content to the base With the above assumptions and using the stated hardware, the node requires a total of energy per day or 7040 mAh in a year. To meet the above requirements, Liion battery pack of 8Ah capacity is sufficient. Solar charging would further improve the life time of nodes. In the Table 1 we will represents Transmit mode by ―Tx‖, Receive mode by ―Rx‖ and Power Down by ―PD‖. The average current (in milli Ampere) requirements of ponents in different modes are given in Column 4. Column 5 ―T‖ gives the typical time (in sec) taken by sensors and other peripheral to take single reading. Last column . ―C‖ is the per day current requirements (mAh) of ponents in different mode. TABLE I. NODE LIFETIME ESTIMATION IV. CONCLUSION This paper presents an operational prototype for wildlife monitoring using WSN. wildCENSE is pact, accurate and does energy efficient sensing. Besides being energy efficient, it provides detailed position logs with a very high accuracy. The software protocols and the hardware implementation have all been carefully crafted to optimize the systems energy requirement. Though units like the GPS and Radio transceiver consume considerable energy, utilizing the sol。C and % RH). This sensor is shielded by a cap (IP67 standard) which lets it sense the environment but at the same time protects it from the same. We use a high sensitivity digital light sensor from TAOS, TSL2561t [15]. To monitor the activity of the animal an analog accelerometer from Freescale Semiconductor MMA6270QT [16] is used. This data along with the position logs provides more insight into the migration pattern of the animal as well as its microclimatic preferences. The node has been designed employing numerous noise reduction techniques. To reduce the ADC noise, a LC filter (L=10mH and C=) has been added to the ADC pins of the microcontroller. Also, the AVCC is connected to the main power supply without any in between fan out lines, to reduce noise [6]. The whole PCB has copper pouring to keep the noise at a minimum level as also to dissipate any heat generated by the node. Figure 3 depict the node. The size of the node is 5 x 6cm2, weighing only 34gms. Including the power supply (Liion battery with solar charging mechanism), the total weight of the system, excluding the collar is less than 300gms (using 4 LiIon cells weighing 148 gms). (a) (b) Figure 3. wildCENSE node, (a)top view (b)bottom view 2)Software Architecture Addressing the main design constraint, the energy。 wildlife tracking I. INTRODUCTION Wireless sensor works (WSN) invariably employ sensing from spatially distributed autonomous nodes. With a little jugglery of sensors, microcontrollers, radio transceiver and an energy source, lowpower and inexpensive sensor nodes (we’ll simply call them nodes) can be made to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion etc. at different locations. The task bees more challenging when the nodes are mobile. To further question the engineering effort is the case, where the node’s power supply should be sufficient for it to last years. Hence the acquisition, accumulation and relay of data impose a great challenge on the WSN39。 英文原文： wildCENSE: GPS based Animal Tracking System Abstract—wildCENSE is a Wireless Sensor Network (WSN) system which attempts to monitor the behaviour and migration patterns of Barasingha (Swamp Deer). The system would collect the microclimatic as well as positional information of the animal and municate it to a base station through flooding of data using peertopeer work. The base station, using a gateway, upload all the collected data to a database server on Int