Not only in India, but globally, technologies such as RFID, IoT, BLE, UWB, and GPS are being used for automation purposes. While these technologies can capture accurate data at various operational levels, more modern technologies like Big Data, Machine Learning, and AI are used to extract meaningful insights from the data collected in warehouses, logistics hubs, retail stores, and manufacturing plants.
However, the right implementation of these technologies is necessary in order to extract meaningful outcomes. For example, RFID technology requires you to understand how tags, readers, and antennas work, and how factors like interference from metal and liquids, collisions, orientation, receiver sensitivity, antenna gain, etc., affect the performance of the RFID system being implemented.
In this blog, let’s explore a similar factor known as RFID tag shadowing, affecting RFID tag reading in high volume environments such as libraries, file and document management in offices, govt. Firms, legal entities, pallet tracking in warehouses, jewelry tracking, inventory tracking, apparel and food item tracking in retail, etc.
What is RFID Tag Shadowing?
RFID tag shadowing occurs when one RFID tag obstructs other RFID tags in the vicinity, shielding the RF energy from RFID reader signals from reaching other RFID tags, effectively hampering the reading of these tags.
This usually happens when one tag is placed in front of the other tag or overlaps with the tag for receiving higher radio frequency energy from the reader. Hence, the shadowed RFID label fails to receive the required RF energy to activate, thus fails to send the response back to the reader, which leads to inaccurate data capturing or inaccurate label readings.
RFID Tag Shadowing is Distinct from Tag Collision
While tag shadowing might seem similar to tag collision, it is slightly distinct. RFID tag collision refers to a situation where, in a high tag volume environment, multiple RFID signals send signals to the reader simultaneously and the reader fails to read all of tags whereas, in an RFID tag shadowing, the problem is caused due to placing two tags facing to each other, where one tag physically blocks the reading of the other tag, as often happens in libraries where similar books, with tag placed on similar spot, face each other with a narrow gap.
The RFID tag shadowing problem is easy to resolve by following a few simple steps while tagging objects with RFID and storing them on shelves or elsewhere.
What Applications Experience RFID Tag Shadowing?
A. RFID Tag Shadowing in Retail Inventory Management: Front tags can obscure back tags in terms of RF signal when they are attached to apparel or other products that are tightly stacked on shelves, display racks, or storage. This can lead to erroneous inventory counts.
B. File Tracking and Document Management Faces Tag Shadowing: When tagged files and document papers are kept side by side in close quarters, and files or documents are being tracked, shadowing may take place, mistakenly preventing the identification of a few specific files.
C.Tag Shadowing in Pallet Inventory/Asset Tracking Applications: If tags are placed in the same plane on pallets containing tagged items, it may be impossible for a reader to read items that are farther away or laterally behind other items. In this case, tag shadowing is used to block tag reads.
D. Tag Showding in Library Management
RFID tag shadowing is a major issue in libraries as well as RFID labels are used on books and journals and these tagged assets are stored on shelves in close, tightly packed environment. More often than not, RFID label on one book faces the RFID label on another, effectively causing RFID tag shadowing.
Steps to Mitigate RFID Tag Shadowing Issues
RFID Tag shadowing can cause inaccurate readings of RFID-tagged assets, leading to inefficient inventory and inaccurate inventory audits. Therefore, it is important to quickly mitigate such issues, which can be done by taking a few steps, including:
1. Improving the Tag and Reader's Position
Physically placing tags on objects and positioning the RFID readers can significantly affect shadowing, even though moving tags adds another burden. To make sure that every tag is exposed to the RF field, for instance, you could adjust the antenna's angle or the position of the tagged item to expose the tags to various read angles.
2. Introducing Motion
It should be feasible to expose the tags to the RFID reader at various angles by moving the handheld reader or the tagged objects through the antenna field. By doing this, read rates will increase and shadowing will be less of a problem. This can be accomplished with mobile handheld readers, tagged objects moving through a read zone on a conveyor belt, or stationary reader locations that can pick up tags from different perspectives.
3. Staggered Tag placement
To increase the likelihood that all tags will be read, tag items in a slightly different order from those in front and behind to prevent direct overshadowing. Storing the items on shelves where RFID tags don’t face each other, but face the staff, is a good strategy.
RFID Reader Collision is Also a Challenge in RFID Systems
RFID reader collision occurs when the signals of two active RFID readers interfere with each other in a warehouse, library, or elsewhere. This interference results in weak communication between the readers and tags, which leads to incorrect reading and inappropriate data transfer.
Reader collision can be identified by two interferences:
1. Reader-to-reader interference: When two or more readers are operating nearby on the same frequency, their signals interfere with each other. This leads to the distortion of weaker tags, making them unreadable and a waste.
2. Reader-to-tag interference: Here, two or more readers try to read the same tag simultaneously. The signals collide even if the readers are using different frequencies. The tag receives signals from multiple readers, which leads to unidentified responses by the tags.
Why choose EnCstore for a Hassle-free RFID Implementation?
EnCstore is one of the best-known RFID solution provider companies in Delhi NCR, offering services all over India. We are a trusted firm in the AIDC industry, whether you require RFID, barcodes, or IoT supplies. We help our clients, offering RFID system implementation strategies that ensure tags are properly read, even if they are densely packed or overlapping. Our services optimise reader placement by using movement to read all tagged assets, as intended.
To summarize, RFID tag shadowing as well as tag collisions are some of the major challenges that make the RFID solution inefficient. Steps must be taken to remove such issues in high volume tag environments such as inventory management, retail, healthcare, legal and corporate offices, govt. institutions, etc.
Frequently Asked Questions on RFID Tag Shadowing
1. What is RFID tag shadowing?
RFID tag shadowing occurs when an RFID tag is shadowed, or covered by another tag, and RF signals cannot reach the obstructing tag. The tag that is shadowed will not be energised, and thus cannot be read by the RFID reader.
2. Is tag shadowing the same as tag collision?
Not at all. Tag collision is when multiple RFID tags respond to the reader at the same time, which creates a mingling of data. Tag shadowing is when a tag is physically obstructed from the RF signal and will not be able to respond as a result.
3. Why not tag shadowing RFID concerning RFID systems?
Shadowing results in less than complete reads, a decrease in inventory accuracy, and no reliability in tracking, ultimately risking the RFID-based system being inefficient.
4. Where does RFID tag shadowing typically occur?
1. Inventory or storage systems at retail with stacked items
2. Palletised inventory in warehousing
3. Stacked or closely placed files/documents
4. Books are packed tightly in libraries
5. Clothing is arranged in piles in clothing shops
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