'Passive' RFID tags broadcast their location but have limited transmission range (typically a few meters). Longer-range "smart tags" use 'active' RFID -where a radio transmitter is powered by a battery and can transmit up to 2000 meters (6,600 feet) in optimum conditions. RFID-based Asset Tracking requires an infrastructure to be put in place before the whereabouts of tags may be ascertained. An asset tracking system can record the location and usage of the assets and generate various reports.
GPS asset tracking
Assets may also be tracked globally using devices which combine the GPS system and mobile phone and/or satellite phone technology. Such devices are known as GPS asset trackers and are different from other GPS tracking units in that they rely on an internal battery for power rather than being hard-wired to a vehicle's battery. The frequency with which the position of the device must be known or available dictates the quality, size or type of GPS asset tracker required. It is common for asset tracking devices to fail due to Faraday cage effects as a huge proportion of the worlds assets are moved via intermodal containers. However modern tracking technology has now seen advances in signal transmission that allows enough signal strength to reach the GPS satellite system which can then be reported via GPRS to terrestrial networks.
Wi-fi, IR, and Bluetooth
For indoor asset tracking Wi-fi combined with another technology like IR has been used. Bluetooth technology has also been used, and may provide more accuracy even if Bluetooth technology wasn't primarily developed for localisation.
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