iLocate implemented the RFID readers by adopting 0.18-μm
CMOS integrated circuits owing to its ultralow power consumption
and robustness to high-risk scenarios such as gas
stations and mines. The RFID readers were configured with
several omnidirectional antennas. Both the RFID readers and
tags were implanted with a module of the direct frequencyhopping
spectrum spread. The RFID coordinators were made
by extracting the communication and simple instruction processing
capabilities. The RFID coordinators were in charge of
waking up and activating the active tags. To build large-scale
RFID networks, iLocate employed the commercial off-the-shelf
ZigBee transmission module. Fig. 7 shows the majority of the
hardware we used in the iLocate system.