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SmartShelf System
RFID tracks status of items on retail and library shelves in real time.
by Eddie TAN Beng Sing

eeping an accurate inventory of shelved items in real time constitutes one of the most desired attributes in any retail business, resource collection, or library system. It further enhances the efficiency of such industries or businesses if they can carry out inventory keeping in a very short time, such as within seconds per tier.

A Radio Frequency Identification (RFID) system offers an ideal way to track how often an item gets removed from or looked at and returned to a shelf. RFID uses radio-frequency communication to identify, track, and manage objects or living things via a readerand- tag system. An item fitted with RFID tag couples radio signals that a RFID reader receives to obtain the details.

Researchers at the Institute for Infocomm Research (I2R) in Singapore have been investigating the application of RFID in various situations. They came up with the SmartShelf System as their solution to the problem of monitoring and locating misplaced or wrongly placed items.

The invention provides a 13.56MHz high-frequency RFID solution, designed to provide real-time tracking and location of tagged items on shelves at all times. It offers cost effectiveness, ease of use, and simple installation on different types of shelves, including metal ones. The developers solved challenges in smartshelf application such as electromagnetic shielding from typical metal shelves, space constraints of the shelves' tiers, conformance to shelf and tagged items, controllable coverage of antennas, 100% reading accuracy, as well as electromagnetic interference (EMI) and electromagnetic compatibility (EMC) problems.

The inventors have addressed these challenges by incorporating numerous creative innovations.

The SmartShelf System comprises an RFID reader, an antenna multiplexer, a wireless gateway controller, reader antennas, and access control devices (see figure).

The antenna multiplexer can have multiple antennas connected to the RFID reader, greatly reducing implementation cost. It has a low-loss, easily programmable, and cascadable antenna multiplexer. The user can customise and optimise the number of multiplexer output ports to suit the shelf configuration of the deployment site, with cascading capability of up to three levels. For example, a user can connect a 10-port antenna multiplexer (level 0) to another 10 multiplexers (level 1), the level 1 multiplexers to another 100 multiplexers (level 2), and the level 2 multiplexers to 1,000 antennas.

The wireless gateway controller with both wired and wireless communication capability provides communication between access-control devices and the RFID reader and antenna multiplexer. Its makers engineer the controller to enable ease of installation, control, and access.

The access-control devices can be a desktop computer, a notebook computer, or even a personal digital assistant with Ethernet communication capabilities. They are installed with the software program to send control commands and receive RFID data to and from the wireless gateway controller.

The reader antenna receives data from the tags by electromagnetic coupling. Its efficiency and field distribution determine the system's reading accuracy and reading range. I2R has created various patent-pending designs for both horizontally and vertically placed reader antennas. The reader antennas can work on metal shelves, which otherwise significantly affect the RFID magnetic field. The project team developed an innovative horizontal bottom-placement antenna that covers the whole tier with 100% reading accuracy by using only one antenna on a metal shelf -- possibly a world-first.

To achieve total reading accuracy and coverage, the reader antennas must offer uniform field distribution and a controllable coupling zone. The horizontally placed antenna based on the patent-pending technologies removes the nulls in conventional loop-type antennas. With uniform field distribution, the user can control coverage to alleviate the EMI and EMC issues between adjacent tiers and shelves.

The reader antenna requires minimal retrofitting onto existing shelves. Using a single-piece antenna requires less connectivity than a costly antenna multiplexer and radio frequency cables, thereby significantly reducing the total system cost further.


The user can program the SmartShelf System to perform specific applications, such as stock taking, periodic scanning, browse counting, item searching, misplaced-item reporting, database updating, and so on.

For example, the stocktaking function provides selection of the particular tier or shelf or all the shelves scanned by the system. Each individual tier is uniquely identified. The browse-count function tracks how often an item gets browsed, that is, removed and put back. Periodic scanning can determine the browse count.

In the library application, the search-item function allows a user to search for an item on the shelf with the option of using a keyword like "author" or "book titles." The National Library Board in Singapore is currently working on a pilot deployment of the SmartShelf System at its Sengkang Community Library. The trial system enables librarians to take stock of the books in real time within minutes. Library users will no longer be frustrated in their search for a misplaced or lost book that the current library database system wrongly designates as available. The SmartShelf System will provide the users with the exact locations of available books. The library can collect statistics on the popularity of the books based on the frequency a reader browses them, helping in decision-making about additional copy acquisitions.

In the retail industry, keeping adequate stock on the shelves and ensuring product placement in desired locations at the appropriate time are critical. The SmartShelf System can help here and go a step further by automatically sending stock requests to the back room, warehouse, or supplier. Suppliers and retailers can also collect data and keep track of the time a product stays at a specific location in the retail supply chain. Even home users will find such a system useful as it helps to identify items already at home to prevent purchase duplication and avoid food waste.

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