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Tham khảo tài liệu 'wireless sensor networks application centric design 2011 part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Wireless Sensor Networks for On-field Agricultural Management Process 19 A WSN system was developed according to the afore mentioned requirements. The system shown in Fig. 1 comprises a self-organizing mesh WSN endowed with sensing capabilities a GPRS Gateway which gathers data and provides a TCP-IP based connection toward a Remote Server and a Web Application which manages information and makes the final user capable of monitoring and interacting with the instrumented environment. TCP-IP over GPRS NODE 3 NODE 1 WEB INTERFACE NODE 2 SERVER Fig. 1. Wireless Sensor Network System GPRS GATEWAY 3. Hardware Design Focusing on an end-to-end system architecture every constitutive element has to be selected according to application requirements and scenario issues especially regarding the hardware platform. Many details have to be considered involving the energetic consumption of the sensor readings the power-on and power-save status management and a good trade-off between the maximum radio coverage and the transmitted power. After an accurate investigation of the out-of-the-shelf solutions 868 MHz Mica2 motes Mica2 Series 2002 were adopted according to these constraints and to the reference scenarios. The Tiny Operative System TinyOS running on this platform ensures full control of mote communication capabilities to attain optimized power management and provides necessary system portability towards future hardware advancements or changes. Nevertheless Mica2 motes are far from perfection especially in the RF section since the power provided by the transceiver Chipcon CC1000 is not completely available for transmission. However it is lost to imperfect coupling with the antenna thus reducing the radio coverage area. An improvement of this section was performed using more suitable antennas and coupling circuits and increasing the transmitting power with a power amplifier thus increasing the output power up to 15 dBm while respecting international restrictions and standards. .
