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I. INTRODUCTION
Radio Frequency Identification (RFID) and wireless RF sensors are the conduit between the physical world and the digital world. These technologies provide the ability to Identify, Locate, and Sense the Conditions of animate and inanimate entities and their surrounding environment, and enable real-time decisions to be made based on that information. Of course, RFID also is changing the way companies do business. Cutting through all the hype, the basic business benefit of RFID technology is improved asset visibility. There is no company in the world that cannot profit from having a more accurate picture of what it has and where it’s located. This in-depth article is designed to help you implement RFID technology successfully. Our goal is create a resource for everyone that wants to understand:
o What is RFID technology;
o Where and why they would use RFID technology,
o And how to implement RFID technology successfully.
There are four basic components to every RFID system:
1) RFID Tags: RFID tags are affixed to assets. Each has a unique numerical identifier so differentiation is possible. For supply chain operations, it is common for the tag identifier to contain the Serialized Global Trading Identification Number (SGTIN) of the item to which it is affixed. This allows differentiation of identical items.
2) Interrogators (or readers)
An interrogator, or more often called a reader, is a radio frequency transmitting and receiving device used to communicate with an RFID tag. The device was named an interrogator because it interrogates the tags. The term "reader" is a more colloquial term, but is sometimes misleading in that many of these devices also have the ability to encode, or write information to an RFID tag. A reader basically acts as a sensor because it senses what tags are within its range and is designed to interface with an information process system, which we'll explain more about below.
3) Antennas
One or more antennas are connected to the reader and are required for the radio frequency communications between the tag and the reader. Antennas come in a variety of size and shapes and have a significant impact on read range and performance.
4) RFID Information Processing Systems
In order to obtain any tangible benefit from RFID technology, the readers must be connected to an information processing system. The information processing system provides instructions to the readers, coordinates their operation, collects output data, and most importantly, makes decisions based on business rules about the data it receives. These computer programs are sometimes called "middle-ware" or "edge-ware." We prefer to call them "Intelligent Sensor Network Platforms" because RFID readers typically need to be coordinated with other industrial devices, such as:
Industrial sensors: photo-eyes, motion detectors, environmental monitors, etc.
Feedback devices: light-stacks, displays, etc.
Automation control systems: triggers, servos, motors, robotics, etc.
An RFID read point refers to a specific antenna connected to a reader (pictured right). A read zone is a logical grouping of one or more read points (pictured left). It is important to point out that the read points comprising a read zone are NOT necessarily connected to the same reader. For example: Read Zone Alpha may be made up of Antenna 1 and 2 from Reader 5 and Antenna 3 and 4 from Reader 6.The primary function of an RFID reader is to report state changes to its environment. A change in state is called an event. There are three types of RFID-related events:
1. A New Tag event occurs when a tag appears to a reader for the first time.
2. A Visibility Changed event occurs when the visibility of a tag changes for a read point.
3. A Tag Not Visible event occurs when a tag is no longer visible to any read point.
A reader captures events along with the date, time, and data from the RFID tag(s) that caused the event to occur. The real benefit is realized from the ability to make decisions based on the events reported from multiple readers. That's where the information processing systems come in. Edge ware or middleware aggregates and filters the event data coming from the readers and may even make decisions based on a defined set of rules. The software may be operating on a stand-alone computer, or an industrial appliance designed specifically for this purpose. In addition to the four basic components (reader, tags, antennas, middleware), more sophisticated RFID systems incorporate monitoring and sensing devices such as electronic switches, photo-eyes, and motion sensors. The events from these devices are combined with the RFID related events for improved decision processing. For example: when the dock door switch is on (door is open), power on the RFID reader, and store all RFID events into the database. RFID systems are often connected to warehouse automation systems that are made up of devices such as Program Logic Controllers (PLCs) pictured left. The events generated by the RFID system triggers these devices to perform various operations. For example: When the RFID reader reports tag 12345, illuminate a stack light.
History and technology background
In 1945 Léon Theremin invented an espionage tool for the Soviet Union which retransmitted incident radio waves with audio information. Sound waves vibrated a diaphragm which slightly altered the shape of the resonator, which modulated the reflected radio frequency. Even though this device was a covert listening device, not an identification tag, it is considered to be a predecessor of RFID technology, because it was likewise passive, being energized and activated by electromagnetic waves from an outside source.
Similar technology, such as the IFF transponder invented in the United Kingdom in 1915, was routinely used by the allies in World War II to identify aircraft as friend or foe. Transponders are still used by most powered aircraft to this day. Another early work exploring RFID is the landmark 1948 paper by Harry Stockman, titled "Communication by Means of Reflected Power" (Proceedings of the IRE, pp 1196–1204, October 1948). Stockman predicted that "... considerable research and development work has to be done before the remaining basic problems in reflected-power communication are solved, and before the field of useful applications is explored."
Mario Cardullo's device in 1973 was the first true ancestor of modern RFID, as it was a passive radio transponder with memory. The initial device was passive, powered by the interrogating signal, and was demonstrated in 1971 to the New York Port Authority and other potential users and consisted of a transponder with 16 bit memory for use as a toll device. The basic Cardullo patent covers the use of RF, sound and light as transmission media. The original business plan presented to investors in 1969 showed uses in transportation (automotive vehicle identification, automatic toll system, electronic license plate, electronic manifest, vehicle routing, vehicle performance monitoring), banking (electronic check book, electronic credit card), security (personnel identification, automatic gates, surveillance) and medical (identification, patient history).An early demonstration of reflected power (modulated backscatter) RFID tags, both passive and semi-passive, was performed by Steven Depp, Alfred Koelle, and Robert Freyman at the Los Alamos National Laboratory in 1973. The portable system operated at 915 MHz and used 12-bit tags. This technique is used by the majority of today's UHFID and microwave RFID tags. The first patent to be associated with the abbreviation RFID was granted to Charles Walton in 1983.
The largest deployment of active RFID is the US Department of Defense use of Savi active tags on every one of its more than a million shipping containers that travel outside of the continental United States (CONUS). The largest passive RFID deployment is the Defense Logistics Agency (DLA) deployment across 72 facilities implemented by ODIN who also performed the global roll-out for Airbus consisting of 13 projects across the globe.
Where RFID technology should be applied?
When determining where RFID technology should be applied within a supply chain, ask, “Where can we benefit from asset visibility?” Typically, asset visibility
is desired when movement occurs (e.g., when the product comes in the dock door, when the product is shelved in the distribution center). Chances are someone in your organization asked where visibility would be useful when designing the manufacturing plants, distribution centers, and other locations across your supply chain. Most likely, these locations have some type of Automatic Identification (Auto-Id) technology already in place, such as a barcode scanner. Manual methods of identification are very common. The standard to which all other identification methods are measured is still a person with paper and clipboard counting what he sees. Contrary to what you may have read, RFID will not completely replace bar codes. Just as human readable information is still used in conjunction with bar codes, RFID technology will compliment barcode technology. RFID only makes sense where it provides advantages over bar codes, and there are five advantages that it has:
Speed
An RFID reader can read tags faster than a bar code scanner can scan bar codes. RFID readers designed for supply chain operations can perform between up to 1,500 read operations per second.
Read Distance
Depending on the equipment configuration, it is not uncommon to read RFID tags at distances of 3 meters between the tag and the antenna. This area is commonly referred to as the "read field". The size and shape of the read field may be controlled by adjusting reader power settings, antenna selection, antenna placement, and other techniques. A read field is three dimensional in that its size may be measured using X, Y, and Z dimensions.
Simultaneous vs. sequential scanning
RFID readers can identify multiple tags within the read field. The most common application of this capability is for the reader to report all tags within its read field.
Non-line of sight
Depending on the frequency being used, radio waves can penetrate most materials. When using the standards being adopted for RFID in supply chain operations there are challenges when working with materials that contain liquid or metal. However, there are proven methods for working around these challenges.
Durability
RFID tags can still operate even if they get dirty. RFID tags can be hardened by encasing them in plastic. Some companies have even embedded RFID tags directly into the products they manufacture.
