Main Elements of RFID that Allow the Technology to Work


Now that you know why companies are using RAIN RFID, let’s take a closer look at how it works. RAIN RFID solutions include three main elements:.

  • Endpoints - an item and its attached RAIN RFID tag chip radio that uniquely identifies the item
  • Connectivity – devices that enable wireless, bi-directional communication with endpoints
  • Software – aggregates and transforms data from endpoint reads, delivering real-time information to enterprise and consumer applications
Endpoints Uniquely Identify Items

In a basic RAIN RFID system, tags are attached to all items that are to be tracked. A RAIN RFID tag is comprised of a tag chip (sometimes called an integrated circuit or IC) attached to an antenna that has been printed, etched, stamped or vapor-deposited onto a mount which is often a paper substrate or PolyEthylene Therephtalate (PET). The chip and antenna combo, called an inlay, is then converted or sandwiched between a printed label and its adhesive backing or inserted into a more durable structure. Finished tags are available in a wide variety of shapes and sizes including labels or stickers, apparel hang tags, security tags, and industrial asset tags used on pallets and heavy machinery. Advancements in RAIN RFID have made it possible to tag liquids and metals. The type of tag needed depends on the item being tagged and where and how connectivity devices will engage it.

Tag Chips

RAIN RFID tag chips uniquely identify their host item and deliver performance, memory and extended features to tags. Tag chips power themselves from a connectivity device’s radio waves so don’t require any batteries, are readable to 30 feet without line-of-sight yet sell for pennies. The chip is pre-programmed with a tag identifier (TID), which is a unique serial number assigned by the chip manufacturer, and includes a memory bank to store the items' unique tracking identifier (called an electronic product code or EPC).

Electronic Product Code (EPC)

The electronic product code (EPC) stored in the tag chip's memory is written to the tag and typically takes the form of a 96-bit string of data. The first eight bits are a header which identifies the version of the protocol. The next 28 bits identify the organization that manages the data for this tag; the organization number is assigned by GS1. The next 24 bits are an object class, identifying the kind of product; the last 38 bits are a unique serial number for a particular tag. These last two fields are set by the organization that issued the tag. The total electronic product code number can be used as a key into a global database to uniquely identify that particular product.

EPC coding diagram

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Tag Antennas

Tag antennas collect energy and channel it to the chip to turn it on. Generally, the larger the tag antenna's area, the more energy it will be able to collect and channel toward the tag chip, and the further read range the tag will have.

There is no perfect tag for all applications. It is the application that defines the tag’s antenna specifications. Some tags might be optimized for a particular frequency band, while others might be tuned for good performance when attached to materials that may not normally work well for wireless communication (certain liquids and metals, for example). Antennas can be made from a variety of materials; they can be printed, etched, or stamped with conductive ink, or even vapor deposited onto labels.

Taking inventory with a RAIN RFID handheld reader is 25X faster than with a barcode reader

Connectivity Devices Identify, Locate, Authenticate, and Engage Endpoints

RAIN RFID readers and gateways are devices that power and communicate wirelessly with tags and deliver tag data to operating-system software. Connectivity devices communicate bi-directionally with endpoints that are within their field of operation, performing any number of tasks including simple continuous inventorying, filtering (searching for tags that meet certain criteria), writing (or encoding) selected tags, etc.

Connectivity devices can identify and locate more than 1,000 items per second. Readers can be stationary or mobile and use an attached antenna to capture data from tags. Gateways integrate stationary readers with scanning antennas to locate and track tagged items. Reader chips and modules are designed for to be embedded in applications like handheld readers, smart vending machines, automotive tracking, mobile devices and more.



Stationary readers require an antenna that sends power, as well as data and commands to endpoints. Since these readers are often used in automated applications they can support additional connections to external presentation sensors or light stacks to notify users of completed reads. Readers and gateways are connected to a host PC or network to transmit all of the tag data.

Reader Antennas

RAIN RFID readers and reader antennas work together to read tags. Reader antennas convert electrical current into electromagnetic waves that are then radiated into space where they can be received by a tag antenna and converted back to electrical current. Just like tag antennas, there is a large variety of reader antennas and optimal antenna selection varies per the solution's specific application and environment.



The two most common antenna types are linear- and circular-polarized antennas. Antennas that radiate linear electric fields have long ranges and high levels of power that enable their signals to penetrate through different materials to read tags. Linear antennas are sensitive to tag orientation; depending on the tag angle or placement, linear antennas can have a difficult time reading tags.

Choice of antenna is also determined by the distance between the RAIN RFID reader and the tags that it needs to read. This distance is called read range. Reader antennas operate in either a "near-field" (short range) or "far-field" (long range). In near-field applications, the read range is less than 30 cm and the antenna uses magnetic coupling so the reader and tag can transfer power. In near-field systems, the readability of the tags is not affected by the presence of dielectrics, such as water or metal, in the field.

In far-field applications, the range between the tag and reader is greater than 30 cm—and in fact can be up to several tens of meters. Far-field antennas utilize electromagnetic coupling and dielectrics can weaken communication between the reader and tags.

RAIN RFID tags can be used on liquids and metals

Software Delivers Endpoint Information to Enterprise Applications



In general, RAIN RFID readers use a standardized language called Low Level Reader Protocol or LLRP.

Software that resides specifically on a hardware component is called firmware, which controls the operation of the device on which it is hosted and does not typically initiate communication with external devices, such as PCs.

Application software sends control commands to connectivity devices and receives tag data, giving businesses access to all the information collected. This software enables businesses to integrate real-time, accurate RAIN RFID data across multiple business applications and may manage reader health, perform remote firmware updates, and configure reader infrastructure.

Creating a RAIN RFID Solution



Were the above details starting to sound a little too complex? The basics of a RAIN RFID system remains the same: endpoints provide unique identifiers and important information to help businesses. Connectivity devices collect and send back data and updates. Software connects these RAIN RFID systems to computers or enterprise applications so users can view data, receive alerts, and run their businesses better. As for the complicated parts, solution providers help optimize a RAIN RFID system for businesses and help implement all the moving parts we just discussed so users can relax and reap the benefits!

Check out our free ebook: How to Choose an RFID Solution Provider


Impinj (NASDAQ: PI) helps businesses and people analyze, optimize, and innovate by wirelessly connecting billions of everyday things—such as apparel, automobile parts, luggage, and shipments—to the Internet. The Impinj platform uses RAIN RFID to deliver timely data about these everyday things to business and consumer applications, enabling a boundless Internet of Things.

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