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Tech Explained: Smart Tags

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Learn how Smart Tags can use radio frequencies to track an item from manufacture to delivery in real-time in our latest Tech Explained feature.

Imagine going to the grocery store, filling up your cart and then walking right out the door. No waiting as your purchases are rung up, no need for pulling out your debit card to pay. Instead, smart radio-frequency identification (RFID) tags allow an electronic reader to detect every item in the cart and automatically deduct the total from your account. This scenario is much closer than you may think. So, how does this smart tagging work, and what other uses will it have?

RFID technology developed out of the use of radar in WWII with the first system created in 1970 to track shipments of nuclear materials. The system used a radio transmitter in the truck with the materials, which would respond with an ID when the truck drove through a receiver in the lab’s exit gates. These original RFID tags were powered by a magnetic field generated by the RFID reader. Like other wireless devices, RFID tags broadcast over a portion of the electromagnetic spectrum. The exact frequency can be changed to avoid interference with other electronic devices. Today, there are three types of RFID tags in common use: active, semi-active and passive tags.

Active RFID tags use internal batteries to broadcast radio waves to a reader. Semi-passive tags, in contrast, use the reader for some of their broadcasting power. Because they have more power for broadcasting, both active and semi-active RFID tags broadcast high frequencies, from 850 to 950 MHz, that can be read as far as 300 feet (100 metres) away. However, they are also costly, and so are generally used to tag items such as railroad cars or shipping containers.

Passive RFID tags, in contrast, rely entirely on the reader as their power source. Because they do not contain batteries, these tags are smaller and cheaper to produce than the active and semi-passive tags, but can only be read up to 20 feet (six metres) away. This is the type of disposable tag found on most consumer goods.

In order to send information, RFID tags also need to be able to store information. There are three types of data storage used with RFID tags – read-write, write-only and write once, read many (WORM). The data on a read-write tag can be added to or overwritten. Read-only tags cannot be added to or overwritten. These tags contain only the data stored in them at the time they were made. WORM tags can have additional data added one time, but they cannot be overwritten.

Most passive RFID tags cost between seven and 20 cents U.S. (16 pence GBP) each, while active and semi-passive tags vary in price according to range, storage type and quantity needed. The RFID industry’s goal is to get the cost of a passive RFID tag down to five cents (four pence GBP) each. Once the tags reach this price level, it will become cost effective to use the tags for tracking a much wider variety of products. It will also be realistic to track the journey of products from manufacture to transport and purchase. In order for this system to work, each product will also need to be given a unique ID number.

At MIT, the Auto-ID Lab is working on developing an Electronic Product Code (EPC) that could replace the current UPC (bar code) system. Under the EPC system, every smart label would contain 96 bits of information, including the product manufacturer, product name and a 40-bit serial number. Using this system, a smart label would communicate with a network called the Object Naming Service. This database would retrieve information about a product and then direct information to the manufacturer’s computers.

We’re not at this point yet, but at the same time as RFID technology is moving forward to label and track more and more items, Near Field Communication technology is also moving forward to deliver contactless payment with greater security. Credit cards or mobile phones with NFC chips embedded in them can already be tapped against NFC payment terminals instead of swiped.

NFC devices can also read passive RFID tags and extract the information stored in them. Combining NFC and RFID opens up a huge number of potential uses, including the frictionless grocery shopping discussed above. At Springwise, we have also seen RFID tags used to track student IDs to prevent dropouts, to aid recycling and to enable self-service in bars.