RFID TECHNOLOGY
2.2 SELECTION GUIDELINE ON TAGS, SERVERS, AND MIDDLEWARE
2.2.3 RFID Device Selection Criteria
To begin the processing of selecting a tag type with an associated reader, you should consider answering the following questions as part of the selection criteria in your economic analysis or a feasibility study.
What are the objects to be tagged?
What are the objects made of and how do they affect reading ranges?
What are chip antenna types?
What readers can read both passive and active tags?
What readers can read both RFID tags and bar code labels for easy transitioning?
What are other considerations that could affect externally the opti- mal location of tags?
How do various entities organize frequency types or ranges?
What other standards are the vendors using for their RFID products?
You can modify or expand the selection criteria to suit your strategies, requirements, and budgets.
2.2.3.1 What Are the Objects to Be Tagged?
The objects to be tagged are pallets, cases, and items in a hierarchical order.
For our own purpose, this order is arbitrarily based on the hierarchy of three layers of object levels, as follows.
Object Level 0: item level Object Level 1: case level Object Level 2: pallet level
The Level 0 layer at the bottom of the hierarchy pertains to products on the item level. The Level 1 layer refers to cases stacked on a pallet and the Level 2 layer pertains to the pallet.
Given the above hierarchy, let’s assume the information stored in a case tag coincides with the information in the database about the products the case holds. We find information stored in a pallet tag points to the infor- mation in the database about the cases stacked on the pallet. If the pallet tag gives information different from that in the database about the cases, then we know the reader did not scan all the cases.
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One possible reason is that the reader may have some problems in reading individual products inside the cases arranged in the center of a pallet, particularly when even rather than odd number of cases are stacked horizontally and vertically on the pallet. It is because in part the reader could not emit enough power to activate tags affixed to cases of items stored in the middle of a pallet stacked with say, 150 cases.
Another possible reason is that the shape and size of the product can affect the optimal location for tags on cases and pallets. For instance, if the product is a bottle of dishwasher liquid tapering at the top, it leaves much air space at the top. The tag should be placed at the upper third of the case, so it will encounter less or no interference from the liquids.
The third reason is that according to Kimberly-Clark, a Wal-Mart supplier, it is better to put tags not on the outside of a case, but on the interior wall of the case or inside the flap. Kimberly-Clark had trouble reading tags on the outside of cases when those cases were stacked on pallets in such a way that the case butted up against the metal of a lift truck. Other reasons for less than optimal reading of tags include white noise from a moving nylon conveyance,the large metal beams in a warehouse, and the steel bar in the foundation of a floor.
Some pilot studies or demonstrations give mixed status on consumer item- level products. For instance, Gillette, a maker of razor blades, has indicated that scaling the products on the item level to a mass production environment is several years away. On the other hand, Texas Instruments reported that a major clothing retailer of jeans successfully conducted the first major field test of RFID for consumer item-level tracking. RFID tags produced 99.9 percent inventory tracking accuracy in distribution centers. So if you are planning or mandated to issue RFID tags for your products on the item level, consider materials of your products when you set up a pilot study.
2.2.3.2 What Are the Materials of the Objects and How Do They Affect Reading Ranges?
If various materials, such as fish, paper products, water, gasoline, and the steel used by rifles are bundled within a pallet, expect an interference with radio signals as it is difficult to transmit radio signals through liquid and metals. The U.S. DoD gets around this interference problem by excluding sand, gravel, liquids, or other types of bulk commodities from its RFID tagging plan.
Passive tags made of certain material work well with certain materials other than metals and liquids. Some active tags, such as Alien’s EPC Class 1 UHF tags, can be applied to metallic and liquid environments to a limited extent.
Passive tags affixed to materials containing metals, high carbon content, or high water content can reduce their read ranges. Collision of radio signals
52 RFID in the Supply Chain: A Guide to Selection and Implementation
between tags, and distance between tags that are outside the frequency field range can interfere with emitted radio signals. The metal of a lift truck against which the passive-tagged cases may be butted up, the large metal beams in warehouses, and the steel bar in the foundation of a floor can reduce the accuracy of tag reads.
Another factor influencing the accuracy of tag reads is the difference in radio frequencies the tags can hold. For instance, 915 MHz and 2.45 GHz Intermec tags give different reading ranges for both metallic and nonmetallic materials. As shown in Table 2.3, 915-MHz passive container tags work best with free space, cardboard, and plastic materials in respec- tive order whereas reusable plastic container tags are well suited for plastic, plywood, and cardboard materials.
Encapsulated metal mount stick tags work best with glass, cardboard, and “free space” materials although their reading ranges are higher than those of the reusable plastic container bags. “Free space” tags work better with “free space,” cardboard, and plywood materials but not at all with metallic (direct contact and 06-in. standoff) material. Container tags perform poorly with metallic materials.
Now, let’s take a look at the reading range of Intermec 2.5 GHz in inches as shown in Table 2.4. Metal mount tags work well with metallic materials whereas the other two tags either perform poorly or not at all with metallic.
CIB Meander tags and metal mount inserts are well suited for plastic, cardboard, “free space,” and plywood materials. Metal mount tags have the lowest reading range of all materials for glass and the other two tags have the second lowest reading ranges of materials for glass.
Table 2.3 Range of Intermic 915-MHz Materials in Feet
Plastic
Metal, Direct Contact
Metal, .06”
Stand-off Glass Cardboard Free
Space Plywood
Container insert 4.5 .5 .5 8 3.5 3.5 6
Container tag 9.5 .25 .75 5 9 13 8
Intelligent ID card
3.5 0 0 1.5 7.5 9 1.5
Reusable plastic container tag
10 1 3.5 4 6.5 6 7
Encapsulated metal mount stick tag
12.5 10 8 13 13 13 12
“Free space” tag 4 0 0 4 11 12 10
Source: Intermec.
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What the results show is that although tags—metallic and nonmetallic—
can be used with metallic materials, their reading ranges are either shorter, little, or none. So if you have metallic materials to which the tags are to be affixed, you need to test tags’ reading ranges. If it is economically and physically feasible, you may wish to change the material to another to get a better reading range.
2.2.3.3 What Are Chip Antenna Types?
Chip antenna is not the same as the reader or conveyor antenna. If the vendor talks about an antenna, you may need to double-check to which antenna type the vendor is referring.
For instance, read-only RFID tags from Matrics (now known as Symbol Technologies) that come preprogrammed with customer-supplied EPC codes are available with one or two antennas. These tags have the read rate of up to 1000 tags per second and long read range of up to 30 feet.
Read-only tags with one antenna are available in five types as shown in Table 2.5. Each tag type indicates what materials it can be applied to, what forms are available, and what the maximum reading distance is.
As you saw, the read-only tags with one antenna of general-use type work best with general-purpose use on plastic, corrugated cardboard, bag- tag, and plastic. They are in the form of inlay, adhesive inlay, and label.
Next in line are rubber encapsulated and UV-protected glass tags that have reading ranges of 15 feet for metal, and glass and windshield, respectively.
The glass bottle and concrete tags have the lowest reading ranges.
On the other hand, the read-only tags with dual antennas can be read from any orientation and are available in three types as shown in Table 2.4.
Each type indicates what materials it can be applied to, what forms are available, and what maximum reading distance is.
Table 2.4 Range of Intermic 2450-MHz Materials in Inches Plastic
Metal, Direct Contact
Metal, .06”
Stand-off
Glass Cardboard Free
Space Plywood CIB
Meander Tag
22 0 9 5 16 16 17
Metal Mount Tag
21 38 43 1.5 28 28 29
Metal Mount Insert
24 0 11 7 19 18 16
Source: Intermec.
54 RFID in the Supply Chain: A Guide to Selection and Implementation
For instance, in Table 2.6, carton tags with dual antenna have the highest reading ranges when applied to corrugated cardboard, paper, or plastic.
General plastic tags with dual antenna have the lower reading ranges, when applied to plastic or wood pallet. The reading range is the same for the paper roll tags when applied to garments, paper, and wood.
For some other tag manufacturers, the higher frequency tags (13.56 MHz) may have a primary advantage over the lower-frequency counterparts (134.2 kHz). For instance, the antenna in a higher-frequency tag may make Table 2.5 Matrics Read-Only Tags with One Antenna
Type Application Form
Maximum Reading Distance (feet) General use General-purpose use on
plastic, corrugated cardboard, bagtag, and plastic
Inlay, adhesive inlay, and label
25
Rubber encapsulated
Metal Converted only 15
UV-protected glass
Glass and windshield UV-protected inlay only
15 Glass bottle Glass bottles Inlay, adhesive inlay,
and label
5 Concrete Embedded in concrete
floors
Adhesive inlay only 5
Source: Symbol Technologies.
Table 2.6 Matrics Read-Only Tags with Dual Antennas
Type Application Form
Maximum Reading Distance (feet)
Carton Corrugated cardboard,
paper, or plastic
Inlay, adhesive inlay, or label
25 General plastic Plastic or wood pallet Inlay, adhesive,
or label
15 Paper roll core II Garments, paper, wood Inlay, adhesive,
or label
15
Source: Symbol Technologies.
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fewer turns than the antenna in a lower-frequency tag. For this reason, the higher-frequency tags may have better capabilities to penetrate nonmetallic materials. This means radio waves of higher frequency can bounce off metal and are absorbed by water. Higher-frequency tags may not be embedded within metal objects with high water content. One way of getting around this problem is to use lower-frequency tags that may have better penetration capabilities. To find out more, check with the manufacturers.
2.2.3.4 What Readers Can Read Both Passive and Active Tags?
Active tags can be combined with passive tags to create a hierarchical visibility of asset tracking in the supply chain. For example, both passive and active RFID are used on conveyance units transporting and loading packaged items.
Active tags’ longer read range provides effective coverage of double doors, dock doors, package counters, wide corridors, and other broad areas that passive systems cannot cover. One caution is that white noise produced by moving nylon conveyor belts may affect the optimal reading of tags.
You need a multi-frequency, multi-protocol reader (also known as
“agile” reader) to read both active and passive tags. This type of reader was pioneered by SAMSys when standards were not well formed. Even with EPCglobal standards in place, agile readers are useful for reading both tag types next to each other. It is particularly useful to switch the mode with the same reader. For instance, in the passive mode with a certain frequency, Wal-Mart was able to read 30 percent of the tags on cases of consumer soap containing moisture. By switching to another mode, Wal-Mart was able to read the tags with 100 percent accuracy.
SAMSys, however, is not the only one offering this type of device. As of July 2003, Savi technology, provider of active tags has collaborated with Matrics (now Symbol Technologies), the producer of passive tags based on EPC standards to develop a handheld device of tracking the shipping con- tainers, trailers, and other conveyances. This would provide a better way of collecting information in real-time on how, say, the container has been broken into and what items are missing or damaged. This information could also include how the items have been shipped.
The handheld device reads Matrics’ passive tags up to 33 feet and writes the data to Savi’s 433 MHz active RFID tags. It can also read active tags up to 330 feet. Matrics offers fixed readers for dock doors, forklift trucks, and conveyor systems. Both readers are based on Savi’s Universal Data Appli- ance Protocol (UDAP). Although this protocol is proprietary, it is the open communications to enable interoperability with other automated data col- lection systems, such as bar-code, RFID, Global Positioning System (GPS), and other hardware-based systems as well as wireless application devel- opment and integration services that can be linked to Web-based Savi
56 RFID in the Supply Chain: A Guide to Selection and Implementation
SmartChain applications. Savi UDAP partners include Alien, Brooks, LXE, Symbol, Intermec, and WhereNet.
As of September 2004, AXCESS Inc. and GlobeRanger entered into a partnership to provide capabilities to incorporate active, passive, and sen- sor-based systems in one package and manage the infrastructure for enter- prisewide, multi-site deployments. AXCESS’ active RFID tags and sensors can enable businesses to monitor, control, and track personnel, assets, inventory, and vehicles enterprisewide and deliver tag data over the net- work to GlobeRanger’s iMotion™ Edgeware™ platform. Data from passive RFID systems can be incorporated with data from sensor data such as temperature, pressure, and motion. As an added feature, an anti-tamper option is available for AXCESS’ active tags. This means when the tag is tampered, it sets off an alert to the appropriate parties in the supply chain.
In response to the trend toward the interoperability of tracking networks of passive and active tagged pallets and cases among NATO networks, Denmark’s Ministry of Defense announced in November 2004 that it con- tracted with Savi Technology to deploy a software platform linked with RFID technologies for tracking and managing supply chain shipments in real-time.
This software platform is designed to be interoperable with RFID-driven networks already developed by Savi Technology for NATO’s Afghanistan Supply Chain, the United Kingdom Ministry of Defence, and the U.S. DoD.
2.2.3.5 What Are Other Considerations that Could Affect Externally the Optimal Location of Tags?
You need to look around in your warehouse or another supply chain facility to see if there are metals affecting the reading of tags. For instance, one of Wal-Mart’s suppliers, Kimberly-Clark, has noted that it is better to put tags not on the outside of a case, but on the interior wall of the case or inside the flap, particularly when the cases are butted up against the metal of a lift truck.
The large metal beams in warehouses and the steel bar in the foundation of a floor can also reduce the accuracy of tags. The white noise produced by moving nylon conveyor belts may affect the optimal reading of tags. If other suppliers do not follow the Kimberly-Clark example, reading tags will not be accurate and it will be very costly to resolve tag location problems.
2.2.3.6 What Readers Can Read Both RFID Tags and Bar Codes for Easy Transitioning?
Bar codes will not disappear overnight when RFID technology is in use as the RFID technology is not fully mature. For easier transitioning to RFID tags for manufacturers and retailers currently using bar-code technology, some vendors are offering hybrid RFID/bar-code scanners and others offer hybrid
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self-check-outs. These hybrid devices allow the executives to evaluate the benefits of RFID technology without disrupting their existing bar-code sys- tem. It also allows them to try out various RFID readers, tags, and other devices, and perhaps RFID specific applications and middleware within their existing infrastructure without making major changes to the system.
For example, PSC (www.pscnet.com) offers Falcon® 5500 Mobile Hybrid Terminal capable of scanning both RFID labels and bar codes. This hand- held device running on the Windows CE-NET Operating System can scan bar-code and RFID-tagged shipments on the same pallet and track them throughout the supply chain, warehouse, distribution center, transportation, and retail store. When the device gets the information, it transfers it to legacy systems possibly via middleware in open system architecture. EPC Class 0 and Class 1 tags can be configured for scanning.
In another example the NCR FastLane™ self-check-out that allows shop- pers to scan both RFID-tagged and bar-coded items was installed in METRO Group’s RFID Innovation Center when it opened in August 2004 in Germany.
In response to privacy concerns, the security function of the RFID tag is deactivated while a self-check-out station scans the merchandise. This allows the customer to carry the merchandise outside the store even while walking in another radio frequency field generated by another RFID reader. This way the information on the merchandise will not be inadvertently picked up by that reader. The NCR FastLane, manufactured by FEIG ELECTRONIC GmbH, supports EPCglobal standards for both Class 0 and Class 1 tags.
In November 2004, the hybrid RFID/bar-code technology was intro- duced into the logistics operations of METRO Group’s Cash & Carry, Real, and Kaufhof stores. In January 2005, NCR Fastlane supplemented conven- tional check-out lanes in 50 of its Real and Extra stores in Germany.
Some other hybrid devices you might want to consider ar e the Memor2000 from MINEC, the 4X terminal, and a handheld device that does not require a shift key to change the mode, Gemini HF 210, a handheld terminal from Blackroc Technology.
An alternative to the hybrid devices is Savi’s UDAP, that allows multiple devices and applications to share information from various Savi partners.
Alien Technology, Intermec Technologies, LXE, Symbol Technologies, RFcode, SAMSys Technologies, and WhereNet are UDAP certified partners.
2.2.3.7 How Do Various Entities Organize Frequency Types or Ranges?
RFID systems come in a spectrum of radio frequencies ranging from 125 KHz through 5.8 GHz. Specifying what frequencies RFID products can carry varies from one vendor to another, from one standard-governing body to another, and from one market research firm to another. In this section, we show how each of the following gives a list of frequency bands: Texas Instruments, AIM Global Network, Forrester Research, EPCglobal, and ThinkMagic.