2009年5月24日 星期日

RF ID Communication System and Frequency Range

    Radio-frequency identification

    Radio-frequency identification (RFID) is the use of an object (typically referred to as an RFID tag) applied to or incorporated into a product, animal, or person for the purpose of identification and tracking using radio waves. Some tags can be read from several meters away and beyond the line of sight of the reader.

    Most RFID tags contain at least two parts. One is an integrated circuit for storing and processing information, modulating and demodulating aradio-frequency (RF) signal, and other specialized functions. The second is an antenna for receiving and transmitting the signal.

    There are generally two types of RFID tags: active RFID tags, which contain a battery and can transmit signals autonomously, and passive RFID tags, which have no battery and require an external source to provoke signal transmission.

    Today, RFID is used in enterprise supply chain management to improve the efficiency of inventory tracking and management.


    Regulation and standardization

    There is no global public body that governs the frequencies used for RFID. In principle, every country can set its own rules for this. The main bodies governing frequency allocation for RFID are:

    Low-frequency (LF: 125–134.2 kHz and 140–148.5 kHz) (LowFID) tags and high-frequency (HF: 13.56 MHz) (HighFID) tags can be used globally without a license. Ultra-high-frequency (UHF: 868–928 MHz) (Ultra-HighFID or UHFID) tags cannot be used globally as there is no single global standard. In North America, UHF can be used unlicensed for 902–928& MHz (±13 MHz from the 915 MHz center frequency), but restrictions exist for transmission power. In Europe, RFID and other low-power radio applications are regulated by ETSI recommendations EN 300 220 and EN 302 208, and ERO recommendation 70 03, allowing RFID operation with somewhat complex band restrictions from 865–868 MHz. Readers are required to monitor a channel before transmitting ("Listen Before Talk"); this requirement has led to some restrictions on performance, the resolution of which is a subject of current research. The North American UHF standard is not accepted in France as it interferes with its military bands. For China and Japan, there is no regulation for the use of UHF. Each application for UHF in these countries needs a site license, which needs to be applied for at the local authorities, and can be revoked. For Australia and New Zealand, 918–926 MHz are unlicensed, but restrictions exist for transmission power.

    These frequencies are known as the ISM bands (Industrial Scientific and Medical bands). The return signal of the tag may still cause interference for other radio users.

    Some standards that have been made regarding RFID technology include:

    • ISO 14223/1 – Radio frequency identification of Animals, advanced transponders – Air interface
    • ISO/IEC 14443: This standard is a popular HF (13.56 MHz) standard for HighFIDs which is being used as the basis of RFID-enabled passports under ICAO 9303.
    • ISO 15693: This is also a popular HF (13.56 MHz) standard for HighFIDs widely used for non-contact smart payment and credit cards.
    • ISO/IEC 18000: Information technology — Radio frequency identification for item management:
      • Part 1: Reference architecture and definition of parameters to be standardized
      • Part 2: Parameters for air interface communications below 135 kHz
      • Part 3: Parameters for air interface communications at 13.56& MHz
      • Part 4: Parameters for air interface communications at 2.45 GHz
      • Part 6: Parameters for air interface communications at 860-960 MHz
      • Part 7: Parameters for active air interface communications at 433 MHz
    • ISO 18185: This is the industry standard for electronic seals or "e-seals" for tracking cargo containers using the 433 MHz and 2.4 GHz frequencies.
    • EPCglobal – this is the standardization framework that is most likely to undergo International Standardisation according to ISO rules as with all sound standards in the world, unless residing with limited scope, as customs regulations, air-traffic regulations and others. Currently the big distributors and governmental customers are pushing EPC heavily as a standard well-accepted in their community, but not yet regarded as for salvation to the rest of the world.
    • ASTM D7434, Standard Test Method for Determining the Performance of Passive Radio Frequency Identification (RFID) Transponders on Palletized or Unitized Loads
    • ASTM D7435, Standard Test Method for Determining the Performance of Passive Radio Frequency Identification (RFID) Transponders on Loaded Containers

    [edit]EPC Gen2

    EPC Gen2 is short for EPCglobal UHF Class 1 Generation 2.

    EPCglobal (a joint venture between GS1 and GS1 US) is working on international standards for the use of mostly passive RFID and the EPC in the identification of many items in the supply chain for companies worldwide.

    One of the missions of EPCglobal was to simplify the Babel of protocols prevalent in the RFID world in the 1990s. Two tag air interfaces (the protocol for exchanging information between a tag and a reader) were defined (but not ratified) by EPCglobal prior to 2003. These protocols, commonly known as Class 0 and Class 1, saw significant commercial implementation in 2002–2005.

    In 2004 the Hardware Action Group created a new protocol, the Class 1 Generation 2 interface, which addressed a number of problems that had been experienced with Class 0 and Class 1 tags. The EPC Gen2 standard was approved in December 2004, and is likely to form the backbone of passive RFID tag standards moving forward. This was approved after a contention fromIntermec that the standard may infringe a number of their RFID-related patents. It was decided that the standard itself does not infringe their patents, but that it may be necessary to pay royalties to Intermec if the tag is to be read in a particular manner. The EPC Gen2 standard was adopted with minor modifications as ISO 18000-6C in 2006.

    The lowest cost of Gen2 EPC inlay is offered by SmartCode at a price of $0.05 apiece in volumes of 100 million or more[55]. Nevertheless, further conversion (including additional label stock or encapsulation processing/insertion and freight costs to a given facility or DC) and of the inlays into usable RFID labels and the design of current Gen 2 protocol standard will increase the total end-cost, especially with the added security feature extensions for RFID Supply Chain item-level tagging.

    Here is the full list of the update on UHF Gen2 Regulation around the world. The list is updated at 2009 January.



    Frequency Ranges

    Because RFID systems generate and radiate electromagnetic waves, they are justifiably classified as radio systems. The function of other radio services must under no circumstances be disrupted or impaired by the operation of RFID systems. It is particularly important to ensure that RFID systems do not interfere with nearby radio and television, mobile radio services (police, security services, industry), marine and aeronautical radio services and mobile telephones.

    The need to exercise care with regard to other radio services significantly restricts the range of suitable operating frequencies available to an RFID system. For this reason, it is usually only possible to use frequency ranges that have been reserved specifically for industrial, scientific or medical applications or for short range devices. These are the frequencies classified worldwide as ISM frequency ranges (Industrial-Scientific-Medical) or SRD frequency ranges, and they can also be used for RFID applications.

Frequency ranges for RFID-Systems

frequency range

comment

allowed fieldstrength / transmission power

<>

low frequency, inductive coupling

72 dBµA/m max

3.155 ... 3.400 MHz

EAS

13.5 dBµA/m

6.765 .. 6.795 MHz

medium frequency (ISM), inductive coupling

42 dBµA/m

7.400 .. 8.800 MHz

medium frequency, used for EAS (electronic article surveilance) only

9 dBµA/m

13.553 .. 13.567 MHz

medium frequency (13.56 MHz, ISM), inductive coupling, wide spread usage for contactless smartcards (ISO 14443, MIFARE, LEGIC, ...), smartlabels (ISO 15693, Tag-It, I-Code, ...) and item management (ISO 18000-3).

60(!) dBµA/m

26.957 .. 27.283 MHz

medium frequency (ISM), inductive coupling, special applications only

42 dBµA/m

433 MHz

UHF (ISM), backscatter coupling, rarely used for RFID

10 .. 100 mW

865 .. 868 MHz

UHF (RFID only), Listen before talk

100 mW ERP
Europe only

865.6 .. 867.6 MHz

UHF (RFID only), Listen before talk

2W ERP (=3.8W EIRP)
Europe only

865.6 .. 868 MHz

UHF (SRD), backscatter coupling, new frequency, systems under developement

500 mW ERP, 
Europe only

902 .. 928 MHz

UHF (SRD), backscatter coupling, several systems

4 W EIRP - spread spectrum, USA/Canada only

2.400 .. 2.483 GHz

SHF (ISM), backscatter coupling, several systems,

4 W - spread spectrum, USA/Canada only

2.446 .. 2.454 GHz

SHF (RFID and AVI (automatic vehicle identification))

0.5 W EIRP outdoor
4 W EIRP, indoor

5.725 .. 5.875 GHz

SHF (ISM), backscatter coupling, rarely used for RFID

4 W USA/Canada,
500 mW Europe

    Table: Frequecy ranges used for RFID-systems (August 2006)

5_RFID-frequencies

    Picture: Frequency-ranges used for RFID-systems shown with the corresponding field strength and power levels.

    Radio Regulation

    The standards drawn up by the ETSI (European Telecommunications Standards Institute) serve to provide the national telecommunications authorities with a basis for the creation of national regulations for the administration of radio and telecommunications.

    for more information about radio regulation please have a look at “Standardization

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