Radio-frequency identification

Introduction

Radio-frequency identification (RFID) is a communication technology, that uses electromagnetic waves to identify and track tags. A RFID system consists out of a tag, which is attached to an object, an reader, which extracts the information of the tag and an application, that uses the gathered information.

RFID-System

Reader

A reader is responsible for initiating the communication with a tag, in case of a passive tag the reader also supplies the energy needed to operate the tag. A reader consists out of to components:

1. A control unit
2. A high-frequency interface

Control Unit

The control unit is responsible for

1. Communication with the application
2. Communication with the tag
3. Coding and decoding of the signal
4. Anti-collision algorithm
5. Encryption and decryption of data sent between reader and tag
6. Authentication between reader and tag

The high-frequency interface is responsible for

1. Generation of strong high-frequency signals to activate the tag and supply it with energy
2. Modulating the transmission signal to send data to the tag
3. Receiving the radio frequency signals transmitted by a tag and converting them back into original data

Tag

RFID tags are divided into six categories by EPC Global. A tag in one category has all the capabilities of the subordinate categories. This means that tags\\ are backward compatible

Passive tags, which have no built-in energy source and draw their energy from the reader's radio waves, are assigned to classes 0 to 3.\\\ Active tags, with their own energy source, are assigned to class 4.\\\ Class 5 is reserved for tag readers and active tags that can read other tags.\cite{rfidiniot}

class 0

Class 0 tags are passive and work with UHF. These tags are pre-programmed in the manufacturer's factory and can no longer be reprogrammed, the information can no longer be changed.

Class 1

Class 1 tags use HF radio waves. In contrast to class 0 tags, class 1 tags and higher can be programmed by the user. However, in class 1, tags can only be described once.

Class 2

Unlike class 1, class 2 tags can be written to multiple times.

Class 3

Read-write with integrated sensors that are able to detect parameters such as temperature, pressure and movement; can be semi-passive or active. Semi-passive means that they occupy an energy source but cannot initiate communication with other tags or readers.

Class 4

Class 4 tags have their own energy source and can initiate communication with other tags or readers, so they are active tags.

Class 5

Class 5 tags are the most advanced, they can transfer energy to passive tags and communicate with readers and tags of any class, so they can also be classified as readers.