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| ==Introduction==
| | #redirect[[Radio-Frequency Identification]] |
| 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.
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| ==RFID-System==
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| ===Reader===
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| 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:
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| <ol style="list-style-type:lower-decimal">
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| <li>A control unit</li>
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| <li>A high-frequency interface</li>
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| </ol>
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| '''Control Unit'''
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| The control unit is responsible for
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| <ol style="list-style-type:disc">
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| <li>Communication with the application</li>
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| <li>Communication with the tag</li>
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| <li>Coding and decoding of the signal</li>
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| <li>Anti-collision algorithm</li>
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| <li>Encryption and decryption of data sent between reader and tag</li>
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| <li>Authentication between reader and tag</li>
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| </ol>
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| The high-frequency interface is responsible for
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| <ol style="list-style-type:disc">
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| <li>Generation of strong high-frequency signals to activate the tag and supply it with energy</li>
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| <li>Modulating the transmission signal to send data to the tag</li>
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| <li>Receiving the radio frequency signals transmitted by a tag and converting them back into original data</li>
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| </ol>
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| ===Tag===
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| 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
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| 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.\\\
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| Active tags, with their own energy source, are assigned to class 4.\\\
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| Class 5 is reserved for tag readers and active tags that can read other tags.\cite{rfidiniot}
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| '''class 0'''
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| 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.
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| '''Class 1'''
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| 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.
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| '''Class 2'''
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| Unlike class 1, class 2 tags can be written to multiple times.
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| '''Class 3'''
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| 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.
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| '''Class 4'''
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| Class 4 tags have their own energy source and can initiate communication with other tags or readers, so they are active tags.
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| '''Class 5'''
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| 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.
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