From a wide range of commercial ZigBee devices, the
XBee-PRO S2 is an appropriate original equipment manufacturer module to establish communication between a WSU and
the WIU because of its long-range operation and reliability of
the sensor networking architecture. The XBee-PRO S2 is a RF
modem with integrated chip antenna, 20-pins, and 13 general
purpose input/output (GPIO) ports available of which four are
ADC. It can operate up to a distance of 1500 m in outdoor
line-of-sight with 170 mA of TX peak current and 45 mA for
RX current at 3.3 V and power-down current of 3.5 μA.