The Internet of Things

RFID is an identification technology in which an RFID tag (a small chip with an antenna) carries data, which is read by a RFID reader. The tag transmits the data stored in it via radio waves. It is similar to bar code technology. But unlike a traditional bar code, it does not require line of sight communication between the tag and the reader and can identify itself from a distance even without a human operator. The range of RFID varies with the frequency. It can go up to hundreds of meters.

RFID tags are of two types: active and passive. Active tags have a power source and passive tags do not have any power source. Passive tags draw power from the electromagnetic waves emitted by the reader and are thus cheap and have a long lifetime.

There are two types of RFID technologies: near and far. A near RFID reader uses a coil through which we pass alternating current and generate a magnetic field. The tag has a smaller coil, which generates a potential due to the ambient changes in the magnetic field. This voltage is then coupled with a capacitor to accumulate a charge, which then powers up the tag chip. The tag can then produce a small magnetic field that encodes the signal to be transmitted, and this can be picked up by the reader.

In far RFID, there is a dipole antenna in the reader, which propagates EM waves. The tag also has a dipole antenna on which an alternating potential difference appears and it is powered up. It can then use this power to transmit messages.

RFID technology is being used in various applications such as supply chain management, access control, identity authentication, and object tracking. The RFID tag is attached to the object to be tracked and the reader detects and records its presence when the object passes by it. In this manner, object movement can be tracked and RFID can serve as a search engine for smart things.

For access control, an RFID tag is attached to the authorized object. For example, small chips are glued to the front of vehicles. When the car reaches a barricade on which there is a reader, it reads the tag data and decides whether it is an authorized car. If yes, it opens automatically. RFID cards are issued to the people, who can then be identified by a RFID reader and given access accordingly.

The low level data collected from the RFID tags can be transformed into higher level insights in IoT applications. There are many user level tools available, in which all the data collected by particular RFID readers and data associated with the RFID tags can be managed. The high level data can be used to draw inferences and take further action.