September 24, 2005
Gen 2 tags
The most widely used UHF RFID protocol is expected to be the EPCGlobal Gen 2. However, it will not be the only protocol in use. There is a likelihood of a multi-protocol environment for the duration till Gen 2 tags, printers/encoders become available for widespread use. Suppliers to the DoD will be allowed to continue using EPCGlobal Class 0 and Class 1 tags for a period of two years after the introduction of Gen 2 tags.
In a multi-protocol environment, a single reader should be able to read the tags based on different protocols or there can be different readers for different tags; the latter undoubtedly is an expensive alternative and also a space consuming one. Multi-protocol readers that use Software-defined radios (SDR) provide flexibility and an inexpensive solution to the problem. With SDR, the software carries the support for the frequencies and standards; it is not hardwired into the system. This allows an upgrade by the simple process of a download without having to replace devices.
Companies have to consider not only multi-protocol readers but also the multi-protocol tags as well. Thus, it is important to protect the investments and work toward migrating to new standards in a cost-effective manner. A printer/encoder equipped with SDR can again be upgraded by downloading the software.
The Gen 2 standard has been developed as a flexible standard that has several optional features. EPCGlobal Gen 1 specified a frequency range of 860-930 MHz and EPC data of 64-96 bits. EPCGlobal Gen 2 specifies a frequency range of 860-960 MHz and EPC data of 96-512 bits. The air interface and modulation protocols in Gen 2 allow it to fulfill several international radio requirements. EPCGlobal Gen 1 has a minimum write speed of 3 tags/second; read verification is provided but the write verification is optional and is carried out by the encoder. It supports only a limited capacity to add and rewrite data and provides security with an 8-bit password.
The EPCGlobal Gen 2 standard assures a minimum write speed of 5 tags/second with both read and write verification. It ensures unlimited add/rewrite capacity and a 32-bit password. The password can be used to lock or kill the tag and has reversible and irreversible memory locks.
The manner in which the vendors treat the standards will add to the variability in RFID systems. Tags designed to comply with the Gen 2 standard may have chips that vary in size, memory, security, etc. The printers and readers will have to consider the compliance issues in the US and Europe. In fact, Gen 2 tags will be available in hundreds of variations.
Gen 2 tags will use the UII memory that supports larger data structures. The option of unlimited user tag memory will be provided. This will facilitate the addition of proprietary information on the tag at any point in the supply chain, such as expiration dates and time and date stamps, etc. The manufacturer of the chip and smart label inlay are the two factors that determine the size of the memory.
Write verification is essential to prevent the circulation of unencoded and corrupted labels. Printers and encoders usually stop and flash an error message if there is a problem related to the encoding of tags.
Different tags will have different power requirements depending upon their inlays. The type of chip, antenna design, and antenna size determine the amount of power required for an encoder to write data to a tag. In the absence of sufficient power, the chip may not be able to carry out the programming; excess power can lead to data errors. In both the cases, the tag will not be printed. The 32-bit password stipulated by the Gen 2 protocol allows for locking blank memory to protect it from misuse and accidental encoding.
It is likely that the Gen 2 chips will have a range of functionality and features that differ from chip to chip but at the same time will be compliant with the standard. This will mean that companies will have to ensure that the smart label media matches the type and model of printer/encoder used. It will be necessary to have a flexible and easy to upgrade RFID infrastructure in order to keep the cost of ownership down. The infrastructure should be able to simultaneously support the different protocols like Gen 1 and ISO; should be able to satisfy user requirements in terms of features and options; and enable easy upgradation. Since upgradation is a critical issue, the following aspects should be considered:
• Are the upgrades provided free by the vendors?
• Who will pay for the routine support and installation of upgrades?
• What is the procedure for upgrades, can it be done by downloading the software, does it require a hardware upgrade, does the equipment have to be taken to the vendor’s premises, etc.?
• Will an upgrade affect the ability of the printer/encoder to support the different protocols?
It is important to consider the requirements for a multi-protocol system as they may affect the cost of ownership as well the cost of upkeep and upgrading.
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