GB/Z 36442.1-2018Information technology - Radio frequency identification for item management - Implementation guidelines - Part 1:Passive UHF RFID labels (English PDF)

Foreword

GB/Z 36442, Information technology - Radio frequency identification for item management - Implementation guidelines, is planned to consist of the following parts: Part 1: Passive UHF RFID labels; Part 3: Implementation and operation of UHF RFID interrogator systems in logistics applications.

This part is Part 1 of GB/Z 36442. This part was drafted in accordance with the rules given in GB/T 1.1-2009.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. The issuing body of this document shall not be held responsible for identifying any or all such patent rights.

This part was proposed by and is under the jurisdiction of the National Information Technology Standardization Technical Committee (SAC/TC 28).

The drafting organizations of this part are China Electronics Standardization Institute, Shenzhen Invengo Information Technology Co., Ltd., Article Numbering Center of China, China Academy of Telecommunication Research of the Ministry of Industry and Information Technology, and Shanghai Baosight Software Co., Ltd.

The main drafters of this part are Jin Qian, Geng Li, Feng Jing, Wang Wenfeng, Wu Yueshan and Yang Jun.

Introduction

The performance of RFID devices, in particular those operating in the UHF band (800/900 MHz), is strongly affected by factors such as the construction of the RFID label, its position on the item and the RF characteristics of the item to which it is attached. Compared with traditional bar code labels, the selection and placement of RFID labels should therefore be considered more carefully.

This part of GB/Z 36442 provides background, reference material and practical knowledge on the selection and application of passive UHF RFID labels for the transport units and pallets used to ship and distribute commercially packaged goods (layers 2 and 3 of Figure 1). RFID on transport units and pallets can be implemented either with passive RFID labels or by embedding or attaching inlays in traditional labels, tickets and tags.

The key points of this part are: a) passive UHF RFID labels may be placed separately from the human-readable label, the machine-readable label or other identification information on a transport unit or pallet, but in application it is very important that all three are present on the transport unit or pallet; b) the reliability of passive UHF RFID labels should be enhanced so as to reduce the missed-read rate.

Figure 1 illustrates the layers of RFID supply chain applications: layer 0, product tagging (ISO 17367); layer 1, product packaging (ISO 17366); layer 2, transport units (ISO 17365); layer 3, returnable transport items, i.e. unit loads or pallets (ISO 17364); layer 4, freight containers (ISO 17363), for example a 12.192 m (40 ft) ocean container; layer 5, conveyances (trucks, aircraft, ships, trains).

1 Scope

This part of GB/Z 36442 gives guidelines for the selection of passive UHF RFID labels (hereinafter referred to as "RFID labels") and for the selection of media, adhesives, facestocks and inks, and describes techniques for mitigating electrostatic discharge so as to reduce damage to RFID labels.

This part gives guidelines for placing and attaching RFID labels on conveyable cases and containers, on pallets/unit loads, and on non-conveyable items and items that cannot be palletized.

This part provides guidance for RFID labels used in logistics applications and for their packaging.

2 Normative references

The following documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 17626.2-2006, Electromagnetic compatibility - Testing and measurement techniques - Electrostatic discharge immunity test (IEC 61000-4-2:2001, IDT).

GB/T 19946-2005, Packaging - Bar code and two-dimensional symbols for shipping, transport and receiving labels (ISO 15394:2000, IDT).

GB/T 29768-2013, Information technology - Radio frequency identification - Air interface protocol at 800/900 MHz.

GB/Z 36442.3, Information technology - Radio frequency identification for item management - Implementation guidelines - Part 3: Implementation and operation of UHF RFID interrogator systems in logistics applications.

ISO/IEC 15434, Information technology - Automatic identification and data capture techniques - Syntax for high-capacity ADC media.

ISO/IEC 15459-5, Information technology - Unique identifiers - Part 5: Unique identifier for returnable transport items (RTIs).

ISO 17364, Supply chain applications of RFID - Returnable transport items (RTIs).

ISO/IEC 18046 (all parts), Information technology - Radio frequency identification device performance test methods.

3 Terms, definitions and abbreviations

3.1 Terms and definitions. For the purposes of this document, the following terms and definitions apply.

3.1.1 passive RFID tag: a tag consisting of an RFID integrated circuit (chip) connected to an antenna, where the antenna is used both for two-way wireless communication and for harvesting energy from the RF signal transmitted by the interrogator to power the RFID chip.

3.1.2 inlay: the embedded layer of an RFID label, consisting of the chip, the antenna and the substrate to which they are attached [GB/T 29261.3-2012, definition 05.04.03]. Note: see Annex A for its design forms.

3.1.3 transport unit: 1) totes, sleeves, trays, parcels (kraft paper or polyethylene wrapping), bags, sacks, rigid containers (tubs, drums) and the like; 2) a transport package or unit load.

3.1.4 primary package: 1) the initial wrapping or sealing of a product (Note: in some cases the primary package is itself the transport unit or pallet, see Figure 1); 2) packaging in direct contact with the product [ISO 21067:2007, definition 2.2.2].

3.1.5 media: physical items such as labels, tags and tickets. Note: in this part the term refers specifically to RFID-enabled media, i.e. media containing a passive RFID device (label or inlay).

3.2 Abbreviations. ESD: Electro-Static Discharge; LED: Light Emitting Diode; PET: Polyethylene Terephthalate; PVC: Polyvinyl Chloride Polymer; RFID: Radio Frequency Identification; UII: Unique Identification of Item; UHF: Ultrahigh Frequency.

4 Selection of RFID labels

4.1 General. Passive RFID label chips operating in the 800 MHz/900 MHz range should conform to the requirements of GB/T 29768-2013.

4.2 Frequency and power of labels. According to the requirements on frequency and power of the national radio regulation "Provisions on the application of radio frequency identification (RFID) technology in the 800/900 MHz band (trial)", the frequencies used for UHF RFID technology are 840 MHz to 845 MHz and 920 MHz to 925 MHz, with a maximum effective radiated power of 2 W.

4.3 Design factors of RFID labels. RFID label antennas can be manufactured in many ways, and antennas made by different methods have different electrical and mechanical characteristics. When RFID labels are applied to transport units or pallets, it is important to confirm that the media chosen for the RFID label meet the performance specification of the RFID label. The key parameter is range, i.e. the range within which the combination of the RFID label and the transport unit or pallet can be read correctly at the required distance and orientation. ISO/IEC 18046 describes standard test methods; Annex B gives a simple laboratory test method.

4.4 Service life and failure modes of RFID labels. The construction of an RFID label affects its technical performance, service life, environmental adaptability and cost, so the design factors of RFID labels need special consideration.

4.4.1 Flexibility and minimum bending radius of RFID label media. Every RFID label has a minimum allowable bending radius (radius of curvature), which depends on the antenna material and manufacturing process, the chip attachment method and the position and orientation of the chip and antenna on the substrate. Bending the finished RFID label media to less than its minimum radius at any stage of application may crack the antenna or detach the antenna from the chip, causing label failure. RFID label manufacturers should state the minimum bending radius; where this is not available, a rule of thumb is that the bending radius should not be smaller than the radius of the core on which the labels are supplied. The recommended minimum allowable bending radius is 38.1 mm (1.5 in).

4.4.2 Environmental factors. The environmental conditions for storage and transport and the operating conditions in use should be determined by the user according to the intended use and supplied to the manufacturer; they include, for example, operating temperature and humidity and abnormal environmental conditions of the tagged item. Over its nominal service life the RFID label should withstand the same environmental conditions as the material and case to which it is attached. Extreme conditions and environmental cycling shorten label life; failure modes include chip attachment failure, antenna cracking, antenna corrosion and ESD damage. Where RFID labels may encounter abnormal conditions (open-air storage, desert heat, polar cold or cold-store storage, nuclear or electromagnetic radiation, chemical corrosion, etc.), accelerated life testing should be carried out before application to establish the limitations of the label over its service life.

5 Media bonded with RFID labels

5.1 General. This clause discusses the materials and assembly techniques used in manufacturing RFID labels and hang tags. For a given application the appropriate design depends on many factors: it must suit the specific application environment and also give stable RFID performance over the service life. All these factors affect the cost of the media.

5.2 Composition of media materials. 5.2.1 Pressure-sensitive labels. Pressure-sensitive adhesives are widely used for RFID label media and, if properly selected, meet performance and environmental requirements; Annex A gives basic terminology and key design parameters. The inlay is bonded to the facestock with adhesive, and the back of the inlay is also coated with adhesive to support the RFID label media and prevent air bubbles between the inlay and the transport unit or pallet. RFID labels can also be enclosed in pouches for recirculation and recovery; the pouch is bonded to a facestock and adhesive is applied to its back in a similar way.

5.2.2 Dry-gum (water-activated) labels. These materials are not recommended for RFID label media, because the water used to activate the adhesive affects label performance: water molecules attenuate the UHF signal and reduce read range, moisture changes the conductivity of the adhesive and degrades antenna performance, and residual moisture can corrode or chemically alter the antenna material or chip connections.

5.2.3 Secondarily enclosed RFID labels. RFID labels may be enclosed in paper or plastic pouches attached directly to shipping cases or pallets for item identification. The pouch should be vented to the atmosphere to avoid moisture accumulation and condensation, without compromising its protection against normal environmental hazards such as rain. Pouches usually give additional ESD protection. Pouch adhesives should meet 5.6, but requirements are less strict than for pressure-sensitive labels because the adhesive does not contact the label. The paper or plastic should be transparent to UHF radio waves and UV resistant; most polypropylene, polyethylene, PET and polyester films cause little attenuation of UHF signals. Because plasticizers can corrode copper antennas over the long term, PVC films should be avoided with copper-antenna labels.

5.2.4 Hang tags. Hang tags are RFID labels attached with a cord and are usually used on objects that cannot be moved. Conductive cords may affect RFID performance favourably or unfavourably depending on the case; UV-resistant plastic (or other non-conductive) cords are generally recommended.

5.3 Environmental factors in media design. 5.3.1 General. Many commonly labelled items (including pharmaceuticals and perishable foods) have very strict temperature ranges and shelf lives; in such cases the RFID label only needs to meet the environment and service life of the item. 5.3.2 Operating and storage temperature ranges of RFID labels. Recommended: operating temperature range -45 °C to 65 °C; storage temperature range -55 °C to 70 °C. 5.3.3 Storage of RFID label media. RFID label media should be stored in anti-static (non-conductive) bags or boxes in a cool, dry environment to prevent damage from water or other environmental factors, keep the label paper (conductive) moisture balanced, prevent adhesive degradation and prevent ESD damage to chips. Temperature and humidity should be kept within the manufacturer's specified limits.

5.4 Printable facestock of media. The facestock is the printable surface of the media. Paper and plastic facestocks can be used for RFID labels. Metal foils, metallized plastics, metal-filled plastics or plastics that strongly attenuate UHF signals are generally not used because they interfere with RF communication. Three key factors govern facestock selection: compatibility with the printing process, suitability for the environment of the intended use, and physical protection against destruction of the RFID label. Paper facestocks have the lowest cost but the weakest environmental resistance; UV-resistant plastic and plastic foam facestocks usually give the best outdoor durability, withstand harsh working environments and generally give the best protection.

5.5 Printing methods and ink compatibility. Ink and ribbon types shall match the printing process, and the ink shall match the facestock material to ensure good bar code quality. The environmental resistance and long-term stability of printed images need attention, especially for long outdoor storage: water resistance, sun resistance, UV effects, abrasion resistance and smear resistance. Most inks absorb little RF energy; ribbon or ink suppliers should be consulted to ensure printing does not degrade RF performance. A simple test: first measure the maximum read distance of the unprinted RFID label (see Annex B), then print it with 100 % coverage using the intended process and ink and measure the maximum read distance again with the same settings. If the change is less than 10 %, the effect of normal printing (15 % to 25 % ink coverage) with that ink can be neglected.

5.6 Adhesives for permanent RFID labels and inlays. 5.6.1 General. Two groups of adhesive properties should be considered: a) "tack" (the ease of initial bonding) and set time (the time, in minutes or hours, needed to form a firm permanent bond); b) ultimate bond strength, i.e. long-term bond stability, environmental stability and ageing resistance. In most cases adhesives are selected on the second group. There are two basic types: acrylic adhesives, which have good all-round properties and the best high-temperature resistance, and rubber-based adhesives, which are cheaper, have very good initial tack and are well suited to corrugated cases. The physical and mechanical properties of the adhesive need to meet user requirements.

5.6.2 RF characteristics of adhesives and compatibility with RFID labels. Adhesives are chemically complex mixtures that may be in direct contact with the antenna and so can strongly affect performance: they may absorb RF energy, some components may corrode the antenna (especially etched copper antennas), and many degrade chemically over time, so a label that performs well when first applied may be affected after months or years. The RFID label supplier should be consulted to achieve the expected service life. 5.6.3 Hygroscopic adhesives. Hygroscopic adhesives absorb and bind moisture from the environment, which degrades label performance and adhesive tack; water molecules attenuate the UHF signal and reduce read range, and absorbed moisture can corrode the antenna or chip connections.

5.7 Adhesives for removable labels. Removable adhesives are generally not used for RFID labels because they may fall off accidentally. If a specific application requires removable or repositionable RFID labels, work with the RFID label supplier to obtain an appropriate level of adhesion and a satisfactory service time.

5.8 Release liners (backing paper) for pressure-sensitive labels and inlays. 5.8.1 Purpose. The release liner carries the RFID label during manufacture and handling before it is applied to a case. 5.8.2 Adhesive compatibility and release level. The adhesive and liner coating should match the force required to peel the label from the liner. The release force should be moderate: enough that stiffer labels or inlays nearest the roll core do not detach, yet allowing complete release in the printer-encoder or applicator. Die-cut depth should be controlled to avoid damaging the silicone layer and to allow consistent release in automated application.

5.8.3 Peeling RFID labels and inlays from the liner. A common cause of latent damage is improper manual peeling of self-adhesive labels: people naturally peel the label off the liner, which over-stresses or over-bends the antenna and breaks the antenna circuit or its connection to the chip. Figure 2 a) shows this undesirable method; Figure 2 b) shows the correct method, in which the label is placed face down on a flat surface and the disposable liner is peeled away from the label, minimizing bending. Printer-encoders or applicators with automatic liner stripping should be used wherever possible, since they are designed to minimize bending during release. 5.8.4 RF characteristics of the liner. In practice these are relatively unimportant because the label is removed before application; they matter only during printing and encoding in the label printer, a highly controlled environment where signal loss from RF absorption is easily compensated. Liner RF loss may increase slightly because conductive additives are added to silicone liners to reduce ESD during peeling.

5.9 Avoiding electrostatic discharge (ESD). 5.9.1 General. Many processes easily generate static, including peeling RFID labels from the liner; the problem is worse in dry environments such as deserts, winter and high altitudes. Static charge entering the chip through the antenna may cause permanent failure, loss of stored data or damage. An often overlooked source (especially at low humidity) is the operator printing and applying labels: static accumulated on the operator can discharge through the label when it is taken from the printer or applied to an item. In dry environments surrounded by hazardous materials, label operators should work in an anti-static environment and wear anti-static clothing and wrist straps. 5.9.2 Static source - peeling. Peeling labels from the liner, manually or mechanically, generates static; most label printers and applicators have means to safely dissipate it. 5.9.3 Static source - conveyors. Some conveyor belts generate static through motion and surface friction, which can transfer to labelled items and damage RFID labels. The best prevention is to design or modify conveyor systems to avoid static generation; conveyor suppliers can be consulted for detection and dissipation means.

5.9.4 ESD conformance testing. Where explosives, hazardous chemicals and chemical gases are present, ESD is clearly a safety hazard, and extensive test statistics on RFID labels used on packaging should provide a scientific basis for addressing it. Testing shall be in accordance with GB/T 17626.2-2006. With the RFID label placed for 60 s in a field of peak strength 50 V/m over the frequency range 840 MHz to 925 MHz, it shall operate normally and maintain the integrity of stored data; after an electrostatic discharge of 25 kV it shall still operate normally with stored data intact.

5.9.5 Effects of printer-encoders. 5.9.5.1 General. Two common sources of static in printer-encoders are the unwinding and stripping of the facestock and the ribbon loading process. Especially in dry environments both generate static on the label that can enter and damage or destroy the chip; the solution is to dissipate static safely without damaging the chip, and printer-encoders should be designed to eliminate this source of damage. 5.9.5.2 ESD in thermal transfer printers. Thermal transfer ribbons generate static when the polyester film unwinds from the ribbon roll, appearing as opposite charges on the two faces of the ribbon. Especially in dry environments, the printer shall have metal contacts or anti-static brushes on the inked side of the ribbon so that the charge does not discharge onto the antenna during printing. 5.9.5.3 ESD in laser printers. RFID labels bent while passing through a laser printer may suffer ESD damage; before using such printers their effect on RFID labels should be fully tested, especially in dry environments.

6 Printing and encoding of RFID labels

6.1 Printing methods. RFID labels usually carry unique printed information related to the uniquely encoded data in the chip. The printing method shall ensure that the printed human-readable information, the bar code and the encoded chip data are accurately associated and consistent with the database record. The design and selection of the RFID label and the placement of the inlay within the label (see Annex A) shall be matched to the printer-encoder used.

6.2 Initial detection of the label edge. Printer-encoders usually detect the leading edge of the facestock, or black marks, notches or holes on the back of the liner. The registration marks of the RFID label shall match the registration method of the printer-encoder, and the label sensor should be calibrated for the labels in use before operation.

6.3 Encoding and/or verifying RFID label data. Most printer-encoder systems test the RFID label before and after encoding to verify its function and correct data encoding. Methods and equipment that cannot perform such verification should not be used to encode RFID labels.

6.4 Handling of defective RFID labels. Printer-encoders able to verify function and encoding usually identify defective labels and print a special mark on them (e.g. "VOID"); such labels should be disposed of manually or automatically and not used for identification. When a defective label is found, most printer-encoders try to encode and print the same information on the next label until successful. When producing serially encoded labels, it is recommended to print the label serial number with the same label format program that controls RF encoding, which usually ensures that serial numbers are not lost when a damaged label is encountered and that the next label is reprinted and reprogrammed.

7 Placement and attachment of RFID-enabled media and inlays

7.1 Effect of transport units and their contents on the RF characteristics of RFID labels. At UHF, packaged items and packaging materials respond differently to radio waves of different frequencies. Because UHF penetrates many non-metallic packaging materials, the RF characteristics of the contents affect label performance even when the label is on the outside of the transport unit. Packaging materials and contents may reflect, absorb or be penetrated by RF signals: RF-conductive and reflective materials generally shield the antenna or detune its resonant frequency so it cannot capture enough energy to power the chip and return data to the reader; RF-absorbing materials consume energy from the reader and weaken the signal received by the label so that there is insufficient energy to drive the chip; and different chemical compositions may make an item both reflective and absorbing. Many objects combine these properties.

Figure 3 is a triangle describing the RF characteristics of objects, each ranging from 0 % to 100 % (100 % RF transparent at the top, 100 % RF absorbing and 100 % RF reflective at the base corners), with example corrugated cases containing foam packaging, foil-packed potato chips, bottled water, canned pickles and a metal box. Assuming a UHF reader antenna placed just above the labelled face of a series of corrugated cases, each containing one kind of item: the apex represents a fully RF-transparent unit where energy is neither absorbed nor reflected, and foam packaging absorbs only slightly; metal objects such as metal boxes have high reflectance and low absorption; water has high absorption and low reflection at UHF; pickles in glass jars absorb strongly because they contain electrolytes (salt and vinegar) and water, but the metal lids reflect; foil chip bags reflect RF, but their irregular surface scatters some signal in other directions, so some reflected energy is lost. The basic point is that the higher a transport unit sits in the triangle, the less it affects label readability and the longer its read distance.

The most reliable way to determine whether an RFID label works on a given case is testing and verification by a third-party laboratory. In-house tests using the simple method and equipment of Annex B may also be used to select label type and position for reasonable read distance. However, many transport units can be assessed by common-sense visual analysis.

7.2 Determining RFID label placement by visual inspection. Most transport units, especially those containing irregular metal objects, are both RF reflective and absorbing, and these properties are not uniform over the surface; RF performance is usually better near the edges. In the example of Figure 4, a metal drum is packed in a corrugated case with its top and bottom nested in rigid foam and the middle of the case empty (air); Figure 4 a) shows the cross-section and Figure 4 b) plots the qualitatively estimated RF characteristics of label points A to F on the case surface. Scanning labels at A to F shows: point C is only slightly affected by reflection from the nearby curved drum and has almost no absorption, since there is only air; A and E absorb equally owing to the thick foam, but A has a larger reflective component because the drum top is wider than its bottom; B is closest to the drum surface with thinner foam than F, so B reflects more and absorbs less than F; D is farther from the drum than B with no foam (air only), so both its reflection and absorption are lower than at B. The best label position is most likely point C, least affected by the drum. This gives the rule "climb the pyramid" for finding the best RFID label position.

7.3 RFID labels on objects that are mainly RF reflective. Reflectors or metal surfaces usually detune and/or shield the label antenna, reducing operating range. One approach is to test for a position meeting the read distance requirement: find the least reflective area of the transport unit surface, place a standard RFID label there and check whether the achievable read range is adequate (see Annex B). For reflective materials inside the case, reinforcement of the reflected signal in some directions can actually improve standard label performance, which is not uncommon. Another approach is to use labels designed specifically for reflective surfaces, typically with a spacer of corrugated board or foam under a label with a pre-designed resonant frequency, so that the reflective surface tunes the label to the reader frequency; with proper placement such labels usually overcome reflective objects. For metal transport units, placing corrugated board, plastic, foam or plywood under a label designed for reflective surfaces can significantly increase read range even with a gap of only a few millimetres (e.g. the thickness of a corrugated partition), depending on spacer thickness and label.

7.4 RFID labels on objects with RF absorbing characteristics. Strongly absorbing materials such as liquids absorb energy before it reaches the label and can detune the antenna, which makes labelling liquid containers or other absorbing materials difficult. One approach is testing: find the area of least absorption and detuning on the transport unit surface, place a standard label and check whether the read range is adequate (see Annex B). Labels designed for RF-absorbing objects may also be used and, with proper placement, solve most absorption problems. A method for extending read range on highly absorbing transport units is to line the inside of the corrugated case behind the label with metal foil or a metallized plastic insert placed between the board and the contents, isolating the label from the absorbing contents, and then to use a label designed for reflective surfaces.

7.5 Some common packaging issues. For cases containing paper and/or plastic products, most RFID labels can be placed in many positions, usually where the case carries no identification or control information. For unit loads of primary-packaged liquids it is best to place the label away from the liquid, using a specific area of the transport unit depending on container shape and stacking: for cases of cylindrical cans, a label with a vertically polarized dipole antenna can be placed over the gap between curved cans or near a right-angled corner of the case, and generally the closer to the case edge the better; long-necked bottles often leave a large empty space at the top of the case, where a label with a horizontally polarized dipole antenna is best placed. If the pallet is shrink-wrapped or stretch-wrapped, the label is best applied on the surface of the wrap, not covered by it. See Annex B for test methods.

Packaging-line situations to be addressed include: production-line validation of pharmaceutical packaging (processes, standard operating procedures); polyethylene film sealing, which may need a tamp-blow application method; banding over labels; placing labels near the narrow side of kraft or plastic bags; sack surfaces that are hard to label; conveyor systems and product supports that may damage labels; applying labels after case packing to avoid damage during packing; labels applied during container manufacture that may be destroyed by strapping machines; reader collision issues (see GB/Z 36442.3, printed as GB/T 36442.3); existing production lines; operator training on RFID implementation, which is indispensable; and pallet pack patterns.

Labelling cases of tightly packed metal products (such as canned beverages) is troublesome: the package is not really a corrugated case but a corrugated tray (about 5 cm thick) carrying metal products wrapped in plastic stretch material. Long, narrow RFID labels are then needed to fit the tray; the space for the label is limited and the antenna may span many metal cans. Labels designed specifically for reflective transport units are best in this case.

8 Applying RFID labels to conveyable cases and containers

8.1 General. This clause covers mounting RFID labels on conveyable corrugated cases, trays, bundles (polyethylene or paper banded), bags (plastic or paper) and other objects, with the aim of finding the position most favourable for reliable communication between reader and label.

8.2 Definition of conveyables. 8.2.1 Definition. Conveyables are designed to be carried on belt or roller conveyors, and most transport units are conveyable. They usually follow these commercial specifications: users should specify minimum and maximum dimensions, for example minimum length 22.5 cm, width 10.0 cm, height 7.5 cm, weight greater than or equal to 1.8 kg, and maximum length 122 cm, width 63.5 cm, height 101 cm, weight less than or equal to 2.6 kg [as printed]; transport units shall not be irregular in shape; transport units shall be sealed and remain closed during transport; a risk assessment should be made for transport units containing hazardous objects and liquids; outer packaging may be corrugated board, paper or paperboard, wood, metal, or rigid or large flexible plastic.

8.2.2 Transport units. 8.2.2.1 General. A transport unit is a container for transporting and handling items; it may contain one or more items, items packed in smaller transport units, or bulk goods. In general the RFID label should be placed on the longest side of the transport unit. 8.2.2.2 Recommended RFID label position. Labels are recommended to be placed as follows, even if this separates them from the human-readable and machine-readable symbols. For transport units 200 mm to 1 m high, the label itself or part of the label media is recommended to be placed as shown in Figure 5: bottom edge not less than 25 mm from the natural bottom of the transport unit; top edge not more than 430 mm from the natural bottom and not less than 25 mm from the top; vertical edge not less than 19 mm from the vertical edge of the transport unit; antenna polarization adjusted per 8.3 and/or Annex B to maximize read distance with circularly polarized readers. Figure 5 shows this target area on a case. Labels should be placed in the target area for the most reliable communication, following Clause 7 and/or Annex B. Placement on corners or edges of the case is not recommended because these are often damaged in handling. For transport units higher than 1 m, see 9.3.2.

8.2.2.3 Read range performance requirement. With the reader at the maximum radiated power permitted by radio regulations and a maximum conveying speed of 200 m/min, the selection and placement of RFID labels shall provide a minimum read range of 1 m.

8.2.3 Reusable plastic totes, conveyor trays, etc. Owners of returnable shipping containers wish to mount RFID labels permanently for tracking and recovery. If the RFID label of a returnable transport item conforms to ISO 17364, the unique identifier of the returnable transport item (UII-RTI) and that of the transport unit (UII-transport unit) can be encoded on the same RFID label using the syntax of ISO/IEC 15434. In general, permanent asset-identification labels containing UII-RTI data should, when mounted on containers, follow the guidance for transport unit labels in 8.2.1 and the mounting restrictions of 8.4. When several RTI RFID labels are used on different faces of a returnable container for identification, each should contain the same data.

8.2.4 Other conveyable goods. Bags, woven fabrics, plastic drums and the like that conform to 8.2 can be conveyed. They shall be sturdy enough not to be abraded or damaged by conveyor belts and shall have no loose straps or protruding parts that could be caught in the conveyor. When bags or parcels travel on the conveyor, the RFID label or hang tag should be on one side of the transport unit or facing up so that the printed face is visible.

8.3 RFID reader assumptions. Reader systems on typical conveyors use several antennas. When cases sit naturally on their bottom on the belt with the label always facing one side, two wide-field antennas on opposite sides of the conveyor suffice; when cases are randomly oriented, up to 6 antennas may be needed to read all faces. With more than 2 antennas and belt speeds up to 200 m/min, the reader may not work properly. Reader RF power is set by radio regulations, while the number, position and field extent of antennas are affected by the reader's effective power. Circularly polarized reader antennas are recommended, so that the reader reads equally well whatever the orientation of labels with polarized antennas (e.g. UHF dipoles).

8.4 Use and reuse of transport unit RFID labels. Taking the UII-transport unit RFID label as an example: it serves as a temporary identifier for a single one-way shipment between consignor and consignee, and each shipment uses a different UII-transport unit data structure, i.e. the label is unlocked and reprogrammed to reflect the tracking information required in subsequent use. RFID labels shall not be stacked on top of each other in any of the following cases: when overlabelling a reprogrammed UII-transport unit label, a non-RFID label (simple label) containing human-readable information, bar codes, etc. should be used to cover it; if the current UII-transport unit label cannot be reprogrammed, the old RFID label shall be removed and a new UII-transport unit RFID label applied.

8.5 Use of multiple RFID labels. Taking UII-transport unit labels as an example: the UII-transport unit label is a temporary identifier for one one-way shipment, whereas UII-product package permanently identifies the product in the case. A case with a UII-transport unit label may pass from one consignee to a new consignee, or be returned by the consignee to the consignor; it may then be advantageous to encode both UII-product package and UII-transport unit. When both data structures are used, RFID labels conforming to the ISO/IEC 15434 syntax with different data structures shall be used, one encoding UII-product package and the other UII-transport unit.

9 RFID labels for pallet unit loads and their application

9.1 General. A unit load is one or more transport units or other goods bound together by palletized platforms, straps, clips, glue, stretch wrap, shrink wrap or netting so as to form a single unit suitable for transport, stacking and/or storage. RFID label media and/or permanently fixed RFID labels may be used on pallets and pallet unit loads separately or together; for example, the pallet itself may carry one or more permanent labels to track the pallet, while the unit load on it carries an RFID label identifying the shipment. RFID labels conforming to GB/T 29768-2013 are recommended as the preferred choice.

9.2 RFID reader assumptions. 9.2.1 General. RFID labels on pallets or unit loads are often read at various points during pallet handling by readers operating at 800/900 MHz (GB/T 29768) or other frequencies, so label selection and placement should take all types of readers involved into account. 9.2.2 Portal readers. Portal readers are usually fixed at gates or dock doors and automatically read labels on pallets and unit loads passing through in either direction; they may also be placed temporarily to facilitate unloading of rail cars, trucks or containers. Except where the label is backed by a metal surface (e.g. the metal frame of a forklift), labels should be readable whatever direction they face the reader. 9.2.3 Forklift readers. Forklift-mounted readers may have several antennas to read labels on the pallets and/or unit loads carried; unit load labels may be required to align with the forklift reader antennas to ensure reliable operation. Forklift readers are usually connected wirelessly to the host.

9.2.4 Pallet conveyor readers. These are usually fixed installations similar to transport unit conveyor readers, generally short-range devices with read distance within 1 m and limited field of view. To suit the limited field of view, unit load or fixed RFID labels should be mounted within a relatively fixed zone measured from the bottom of the pallet, see 9.3. 9.2.5 Handheld readers. Handheld readers are often used in pallet-level handling, usually to read unit load labels and record data in a personal data terminal and/or send it wirelessly to the host; they are widely used for reading one-off field-deployed items. They are usually low-power battery devices with shorter read range than typical portal readers and may be combined with bar code readers and/or personal data terminals. The key is that users place the reader close enough to the label for reliable reading.

9.3 Use and placement of RFID labels on pallet unit loads. 9.3.1 General. Each pallet shall carry at least one passive unit load RFID label or, by agreement with trading partners, an active unit load tag. Unit load tracking should use passive RFID labels encoded with the appropriate data structure.

9.3.2 General rules for unit load RFID label placement. These rules are similar to those of GB/T 19946-2005 for bar code labels; in practice the RFID label is generally integrated with the shipping label. With reference to Figure 6: if the pallet is shrink- or stretch-wrapped, the label should be applied to the outer surface of the wrap and not covered by the wrap material; the label should be on the long side of the transport unit with human-readable information parallel to its natural base; the label should be to the right of the vertical centre of the face and at least 5 cm from any edge to avoid damage in handling; the bottom edge of a label containing unit load information should be 81 cm to 122 cm above the bottom of the pallet, and if the pallet load is lower than 51 cm the label should be as high as possible but not less than 5 cm from the natural top of the load; labels should not be placed over seams, and seals or brand stickers should not be applied over them, to avoid interfering with bar code scanning or RFID reading; RFID labels should not overlap other RF tags, with a gap of at least 10 cm between two tags; labels should be applied at a suitable place with minimum risk of damage; labels shall suit the transport and storage environment of the unit load.

Figure 6 shows the shipping label on the pallet load at 81 cm to 122 cm height and at least 5 cm from edges. For selection and placement: with no obstruction between label and portal reader, and the reader operating at maximum permitted radiated power in the designed environment, the read distance of the label on the unit load shall be at least 3 m.

9.3.3 Label data structure. The data structure for ISO returnable transport items (RTI) is defined in ISO 17364 and ISO/IEC 15459-5. UII-RTI is usually used in unlockable form and can accommodate UII-transport unit and UII-product package data structures. 9.3.4 Wooden and plastic pallets supporting ISO 17364. It is assumed here that a unit load RFID label is fitted on the unit load and that a permanent RFID label with the UII-RTI data structure is also fitted on the pallet, facilitating both tracking of the goods and return of the pallet to its owner.

9.3.5 Special cases such as crates, cages and tub-type pallet containers. As shown in Figure 7, when the unit load is in a metal or plastic cage, crate or tub, the RFID label may be applied directly to the pallet container or hung from it; a label applied directly shall have read range meeting 9.3.2. When a hanging unit load label is used, its natural hanging position should keep the label face roughly parallel to the vertical side of the container with the printed face outwards; a non-metallic cord is recommended (see 5.2.4). In its balanced position, with no obstruction between label and portal reader, its read range shall meet 9.3.2. Linearly polarized, circularly polarized or omnidirectional labels may be used as long as the requirements are met. Figure 7 shows optional hanging unit load labels on a wire mesh cage and on a stacked pallet container.

9.4 Permanent RFID labels for pallets conforming to ISO 17364. Pallet owners and pallet leasing companies wish to install permanent RFID labels on pallets for tracking and return. ISO 17364 specifies a data structure, the unique item identifier for returnable transport items (UII-RTI), suitable for this purpose and permanently encoded in permanent pallet tracking labels. ISO 17364 labels using the RTI data structure may be used alone or together with one or both of: a) transport unit; b) product package. Moreover, a label using the UII-RTI data format may not be a unit load RFID label. In general, permanent labels may be mounted at the geometric centre of the pallet support structure or on the corners of the front stringer board. When two permanent pallet labels are placed diagonally on the front boards, both shall carry exactly the same UII-RTI data; particular care is needed in programming and placing labels of the same kind, otherwise the two labels on one pallet may be programmed differently, causing serious misidentification. When several UII-RTI labels identify the same returnable container, each shall have the same UII-RTI data format, and placement of multiple labels shall conform to 8.5.

10 Non-conveyable and non-palletized items

10.1 General. Non-conveyable items are usually too large, too heavy and/or too irregular in shape to be carried on conveyors. The main difference between conveyable and non-conveyable items lies in how their RFID labels or hang tags are read.

10.2 RFID reader assumptions. Non-conveyable items are usually read with handheld readers brought close to the RFID label or hang tag. Such readers may integrate bar code and RFID reading and are usually short-range. To improve readability, users can pull the hang tag away from the item and/or move or adjust the reader position for reliable reading.

10.3 Use of multiple RFID labels. The use of multiple RFID labels on pallet containers and unit loads should conform to 8.5.

11 Regeneration or renewal of RFID labels

11.1 Regeneration of failed labels. When the label data structure is rebuilt from the information in the backup bar code and/or human-readable interpretation to obtain an exact replica of the original RFID label, the identical data header bytes and data structure should be copied so that the CRC-16 value is the same. It should be reconfirmed that the regenerated label is consistent with the existing backup bar code and/or human-readable interpretation.

11.2 Use of the RFID tag identifier (TID). Some applications use the unique factory-programmed tag identification number together with the UII data structure to prevent counterfeit products. In this case, even if the UII data can be recovered from the backup bar code or human-readable characters, replacing a failed label is not feasible unless the database knows the new valid TID replacing the TID of the failed label.

11.3 Modifying the UII data structure. When new content is added or the label data are changed on rewriting, the backup bar code may no longer reflect the current data in the label. Creating a new data structure or changing the existing one in a regenerated label invalidates the original bar code. Note: the data structure of the changed label should have appropriate data header bytes reflecting its current data structure; the invalid bar code may need to be destroyed or covered with a new backup bar code backing up the current label data structure.

11.4 Replacing damaged RFID-enabled labels. If a completely new RFID-enabled label is produced, the old label shall be removed before the new label is applied. The new RFID label shall never be placed over the old one, because the old label interferes with the new label.

12 Human readable interpretation (HRI) backup

12.1 Applications of HRI. HRI is needed as backup of the RFID label data structure where manual data entry has advantages over bar code entry for backing up RFID reader data, and where RFID readers and bar code readers may not be available. In these cases the ability to key in HRI is very important; HRI can also serve as a secondary backup of the bar code data.

12.2 Factors to consider for manual data entry. HRI backup may use octal or hexadecimal encoding with a leading identifier. The biggest problem of manual data entry is keying errors, so ideally the fewest data characters should be entered. The choice between octal and hexadecimal HRI depends on the application: hexadecimal is better suited to data entry with general-purpose keyboards; some handheld devices allow only numeric keyboard entry, in which case octal is more suitable than the relatively shorter hexadecimal and reduces input errors. For example, octal needs about 33 % more characters than hexadecimal, yet on many bar code scanners and portable data terminals all-numeric octal may need fewer total keystrokes. Where HRI may use different numbers of leading zeros, for example an octal-encoded bar code with a hexadecimal HRI, less label area is used; despite the different formats, the label data represented by the HRI shall match those represented by the bar code.

In general, octal HRI is preferable to hexadecimal HRI; in either case the HRI information shall match the bar code information. It is recommended to print human-readable characters in groups of 4 separated by spaces for easy reading and accurate entry, using the largest practicable OCR-B or other suitable font where space allows. Because keying errors cannot be avoided, the HRI of every format of RFID label data structure shall include the CRC-16 check code of the RFID label.

Annex A (informative) Design of inlays or RFID labels

Figures A.1 and A.2 show the common forms of die-cut pressure-sensitive roll and fan-fold inlays or RFID labels. In both figures the die-cut label has width W and length L; the liner (backing) has width S with equal blank margins on both sides; the gap between labels is G, and G together with label length L gives the label repeat distance R = L + G. The die-cut perimeter should not exceed 90 % of (2L + 2W). Figure A.1 shows label roll dimensions, including the reference edge, leading edge and blank margin; the inner diameter of the roll core is C and the outer diameter of the roll is D.

Figure A.2 shows fan-fold (Z-fold) labels, with W, L, S, G and R as in Figure A.1. Perforations should be provided in the gap between adjacent labels for folding. The fan-fold labels finally form a stack of width S, length E and height F; the stack length E should be an integral multiple of R. In Figures A.1 and A.2 the leading edge of roll and fan-fold labels is marked and is assumed to be on the liner about G/2 before the first label, because the tear bar (see Figure A.3) is usually used as the position reference line of the printer-encoder.

Figure A.3 shows the internal layout of a stationary die-cut label in a typical printer-encoder (liner, die-cut label, reference edge, leading edge at the tear bar, label feed direction). The important point is that the position of the RFID chip antenna shall match the position of the antenna in the printer-encoder. The transverse dimension of the RFID label is A and the longitudinal dimension is B; the boundary of the inlay or label antenna is defined by its distance X from the reference edge and its distance Y from the leading edge. The leading edge is assumed to coincide with the tear bar of the printer-encoder when the label is stationary before encoding and printing.

Annex B (informative) Optimizing RFID label placement

B.1 General. Although the visual inspection method of 7.2 can guide label placement, a more quantitative method is available to confirm results in terms of read performance and to determine the best label type, polarization and mounting, helping to ensure that labels on transport units or pallet unit loads meet the minimum read distance requirement. Some suppliers have developed test software to optimize label type and placement, using scientific methods to predict statistical performance at different positions with different label types; labels used in commerce perform differently at different frequencies, power levels and duty cycles. The method in this annex needs minimal equipment but gives only relative (not absolute) measurements of read range performance (not conformance). Data for labels and transport units tested in the same laboratory are easily compared, and meaningful correlation can be obtained by testing the same labels and units in several laboratories. Performance testing should follow ISO/IEC 18046; conformance testing should use ISO/IEC 18047-6.

B.2 Equipment. B.2.1 A large indoor or outdoor site with no large metal objects or vehicles within 10 m in front of and beside the antenna under test: an outdoor car park is a good temporary site; indoors, the ceiling should be as high as possible and the floor non-metallic, and ideally a microwave anechoic chamber is used. B.2.2 A UHF RFID reader of suitable frequency fixed on a stand, with a fixed UHF RFID circularly or cross-polarized antenna: reader and antenna should conform to the national radio regulation "Provisions on the application of RFID technology in the 800/900 MHz band (trial)"; reader output power shall be programmable or manually adjustable; reader and antenna should each have a single antenna connector; readers with integrated antennas may also be used. B.2.3 A computer connected to the reader with the appropriate driver software; any built-in wireless LAN should be disabled. B.2.4 A movable antenna stand (preferably non-metallic) able to adjust antenna height over 0.6 m to 2 m and antenna direction. B.2.5 A plastic or wooden table for holding the transport unit during testing, 75 cm to 90 cm high, sturdy enough to support the heaviest transport unit (24.6 kg); tables of moulded plastic or structural foam are a good choice, and metal fasteners are best replaced by nylon fasteners. B.2.6 A computer and RF coaxial cable may also be needed, see B.4.1.

B.3 Test site setup. The ideal test environment specified in Annex A of ISO/IEC 18046 is necessary for accurate absolute measurements; the simplified method described here is low-cost and sufficient to guide label selection and mounting. As shown in Figure B.1, there should be no walls or metal objects within 10 m of the antenna location; where this is not possible, keep the antenna as far as possible from metal objects in front of it. Note: mounting absorber foam panels or absorber cones on plywood placed on three sides of the test table gives better RF isolation; carbon-loaded black conductive foam also has some isolating effect, especially with one or more foam layers of total thickness at least 10 mm. The antenna (black square in Figure B.1) should be mounted on a stand allowing full height adjustment; if cross polarization is used instead of circular, two poles shall be set along the vertical and horizontal axes. Antenna and stand shall be well grounded. The transport unit on the test table (hatched square in Figure B.1) should be about 3 m directly in front of the antenna; all other equipment should be on a standard table or bench at least 2 m behind the antenna, and no cables should lie between the antenna and the test table. Figure B.1 shows this layout within a circle of 10 m radius [printed as "10 mm" in the figure].

Ensure that no active RFID reader is within 30 m of the transport unit under test in any direction, even if separated by walls, ceilings or floors. In general, mobile phones, cordless phones, wireless headsets or speakers, Bluetooth devices and IEEE 802.11 wireless LANs should not be used within a 30 m radius, because some label antennas resonate at several frequencies and the chip may be activated by external RF sources rather than the test reader and antenna, giving erroneous effective activation threshold power values.

B.4 Equipment installation. B.4.1 RF cabling considerations. The coaxial cable to the antenna should be long enough to allow the antenna to be moved within 1 m of the transport unit with full height adjustment. Connect the antenna port to the antenna connector of the reader, and always use the same cable to avoid measurement errors from different cable attenuation. Poor-quality coaxial cable introduces measurement errors indistinguishable from poor label performance; to prevent this: ensure the cable impedance (usually 50 ohm) matches the RF components and connectors and choose large-diameter, low-attenuation cable; readers and antennas usually use 50 ohm N, BNC or SMA connectors (low-cost 75 ohm F-type CATV connectors should not be used), and gold-plated connectors are recommended for reliability; crimped cable ferrules usually give better long-term connection reliability than threaded-ring ferrules, especially at bends. B.4.2 Reader installation. Reader power levels are set with computer software, usually supplied by the reader manufacturer. If the manufacturer has not calibrated output power, calibration with an RF power meter of suitable frequency range and power is recommended; each power level should be calibrated to the decibel (in dBm or dBW). If the reader receiver has programmable or adjustable sensitivity, it should be set to "default" or "normal" sensitivity.

B.5 Test method. B.5.1 General. The method can be used to evaluate the sensitivity of the RFID chip on an inlay or label, in free air or mounted on a transport unit. The main test is the reader transmit power in decibels at the chip activation threshold, i.e. the power needed for consistently reliable reading. Below this threshold the chip cannot be read reliably, either because insufficient power reaches the label antenna to activate the chip or because the label's backscattered signal is too weak to be detected by the reader's receiver.

B.5.2 Threshold power measurement method. The read threshold is not always obvious. The best reader software attempts a set number of reads, or reads per second, and measures the percentage of successful or failed reads; less useful software may only display successful reads, but the success rate can be estimated from what is seen on screen. A good usable threshold is the reader power (or power attenuation) at a 50 % successful read rate. The key to good testing is always using the same technique. Starting at maximum power and slowly reducing it while monitoring the success rate seems logical but gives inaccurate thresholds because of hysteresis in the chip power circuit. A more accurate method is to switch off reader transmit power between tests and start at the lowest power, increasing gradually until the threshold with about 50 % successful reads is found, recording it in decibels. Within a test, the best comparative result is the lowest threshold power measured.

B.6 Evaluation of RFID labels. B.6.1 General. Most label specifications quote performance in free air, which is not always useful because labels are almost always applied to materials or objects with RF absorbing, reflecting or scattering characteristics; this test setup addresses label testing in more realistic environments. B.6.2 Test setup. An empty corrugated case is a very good fixture: place it at the edge of the test table with the label face towards the antenna. The label sample is recommended to be attached to very thin polyester film or PET sheet with at least 50 mm blank margin for taping during tests; for clean removal, one or more 50 mm lengths of vinyl insulating tape can fix the sample, taped at its edges, at the centre of the case face. Adjust antenna height and direction to point at the central target area of the sample. If the label cannot be activated at maximum reader power, move the antenna closer, first to 2 m and if necessary to 1 m. To ensure sufficient dynamic range, find a distance at which the label is activated at less than 25 % of maximum reader power (i.e. at least 6 dB below maximum). Record the exact distance from the antenna face to the label centre and set this transmit power as the 0 dB reference level for subsequent measurements.

B.6.3 Evaluating the performance of batches of RFID labels. If possible, obtain labels with manufacturer performance data measured according to ISO/IEC 18046. Test representative groups of labels in the same way, recording their free-air threshold power per B.5.2; for reference, mark and keep 3 sample groups: least sensitive, average and most sensitive. The least sensitive samples are particularly useful in evaluating transport units (see B.7), since they represent the "worst case" label performance on the unit.

B.6.4 Evaluating the effect of label orientation. Some label antenna designs are orientation sensitive; this can be evaluated by rotating the label about one or more axes and measuring threshold power at several angles. B.6.5 Effect of packaging materials. Label samples can be applied to or permanently mounted on different packaging materials, and the change in threshold power measured to determine the effect of detuning on read distance; always use material samples of the same size with the label at the centre. Note: some labels mounted on specific packaging materials may perform better than in free air because the material was designed in as part of the antenna resonance (see 7.3). B.6.6 Effect of frequency. Labels on transport units in international freight may need to work at several reader frequencies and power levels; evaluate the same batch with readers and antennas conforming to the radio regulations of different regions to determine acceptability at different frequencies. B.6.7 Combined tests. Any of the above tests may reasonably be combined to reduce the total number of tests.

B.7 Testing of transport units. B.7.1 General. This setup can be used to select quantitatively the best label type, polarization and mounting method on a transport unit. B.7.2 Test setup. Place the transport unit at the edge of the test table with the face to be labelled towards the antenna; adjust antenna height and direction to point at the centre of the target area (see Figure 5). Test labels should be chosen from those already tested (see B.6.3), preferably of low sensitivity to ensure "worst case" performance, attached to very thin polyester film or PET sheet with at least 50 mm blank margin and fixed at the centre of the target area with one or more pieces of vinyl tape about 50 mm long. If the label cannot be activated at maximum power, move the antenna closer, first to 2 m and if necessary to 1 m. Note that if a label mounted on the transport unit cannot be read with the antenna at full power less than 1.5 m from the unit, it may not meet 8.2.2.2 in actual use. Find a distance at which the label is activated at less than 25 % of maximum power (at least 6 dB below maximum), record the exact antenna-to-label-centre distance and set that transmit power as the 0 dB reference level. B.7.3 Measurement. Measure using the threshold power technique of B.5.2.

B.7.4 Building an RFID label position map. Labels can be applied at different positions in the target area (see Figure B.2) to determine the effect on read distance of RF absorption, scattering, reflection or other detuning by the contents. Measure and record threshold power in dB at each test point and compare with the 0 dB reference to build a "position map" of threshold power; the position with the lowest threshold gives the best reading. Figure B.2 shows an example map for a case filled with arbitrary objects, with the 0 dB reference at point H, roughly the centre of the target area (as defined in 8.2.2.2). Values at points A to Q relative to 0 dB are: A +2, B +1, C -1, D -3, E -1, F -3, G +1, H 0 dB, J -2, K -1, L +8, M no read, N +2, P 0, Q +1; they range from -3 dB at D and F to 8 dB at L, and M is a "no read" point where the label cannot be read even at maximum reader power. The best position is D, because it has the lowest threshold and is surrounded by favourable positions, giving better tolerance in actual placement; F, by contrast, is surrounded by unfavourable positions and has less tolerance. The threshold at D is also likely less affected by shifting of the contents. Many label types can be compared this way; some labels may perform better on particular transport units because packaging materials and/or contents were designed in as part of the antenna resonance, as often happens with labels designed for RF reflective materials or on cases of metal objects.

B.7.5 Evaluating label polarization. Some label antenna designs are orientation sensitive; many labels with dipole antennas are placed horizontally polarized. Rotating the label and measuring threshold power at several known angles evaluates this. When the transport unit contains cans, bottles or other vertical cylinders, labels with vertically polarized dipole antennas may be more effective; place labels on the tangent of the cylinders and over the gaps between them and test threshold power. B.7.6 Effect of frequency. Labels on transport units in international freight may need to work at several reader frequencies and power levels; evaluate different label types on the transport unit with readers and antennas conforming to regional radio regulations. The optimum label position may change with frequency, and a compromise position can be found by comparing the position maps at each frequency. B.7.7 Combined tests. Any of the above tests may reasonably be combined to reduce the total number of tests.

B.8 Three-dimensional testing of transport units. A clear variation of this test uses the method of B.7.3 to evaluate the three-dimensional characteristics of passive labels on transport units, by moving the reader around the transport unit at a fixed distance from the label centre, recording the reader position vector and measuring threshold power per B.5.2. A 3D plot of label sensitivity can then be drawn, with the sensitivity vector length defined as: RFID label sensitivity (dB) = maximum power (dB) - threshold power (dB). Label sensitivity is a relative value and always positive; it represents the margin between maximum reader power and label threshold power in each vector direction at constant reader-label distance.

Figure B.3 shows two transport units, SKU A and SKU B, containing different items but using the same type of RFID label, with the 3D sensitivity envelope around each; its shape is determined by the stacking of items inside and the label position. SKU A, on the left, has a complex, non-uniform threshold read pattern with strong sensitivity in some directions and zero in others; on a conveyor it needs precise orientation of reader and transport unit for the best read rate, and the nulls in the threshold distance reduce the likelihood of a successful read as the unit moves at speed along the conveyor. SKU B, on the right, has a highly predictable and uniform read range over the top and around the case and is easily read from any position above or beside it; as the case moves along the conveyor the threshold sensitivity changes slowly, the reader has the longest continuous time to read the label, and the success rate is best even at high speed. For the same object, different label antenna designs can give very different sensitivity patterns: Figure B.3 can also represent two cases with identical contents, where the high-Q or highly directional label antenna on SKU A is strongly affected by the contents while the omnidirectional, content-insensitive label on SKU B is less affected. Here SKU B has the better RFID label sensitivity map.

Bibliography

[1] Xinbuwu [2007] No. 205, Provisions on the application of radio frequency identification (RFID) technology in the 800/900 MHz band (trial), Ministry of Information Industry.