Across time and the extended end-to-end supply chain, several Automatic Identification (AutoID) technologies are utilized, some holistically, and some for distinct supply chain segments. Some of these are relatively simple technologies, while others are much more sophisticated and comprehensive, utilizing an extensive space-based satellite navigation system that provides location and time information in all weather conditions. In today's article, we review those technologies and their pros and cons.
Initially, bar-coding was an early technology used in the supply chain, and it continues to evolve (2D tags) and be widely used in an ever expanding array of applications and industries. However, the bar-code system does have limitations (amount of information, line-of-sight read, and read only, among others), especially when the supply chain goes global.
Enter RFID (Radio Frequency Identification), which overcomes most of the bar-code limitations and efficiently provides information when a tag comes within the vicinity of a reader. RFID takes the barcoding concept and digitizes it for the modern world providing the ability to:
- Uniquely identify an individual item beyond just its product type
- Identify items without direct line-of-sight
- Identify many items (up to 1,000s) simultaneously
- Identify items within a vicinity of between a few centimeters to several meters
RFID, or radio frequency identification, is a technology that presents and shares some similarities with the bar code id system. With RFID, either electromagnetic or electrostatic coupling within the RF part of the electromagnetic spectrum is used in order for signals to be transmitted. RFID system is made up of an antenna and a transceiver, reading radio frequencies and then transferring information to a kind of processing device, and a transponder, an integrated circuit that contains RF circuitry as well as the information that's going to be transmitted.
An RFID system has a wide array of usage. A tag could carry info such the pet owner's name as well as address or even complex instructions, such as assembling a motorcycle. Even some car manufacturers make use of the RFID system for them to move cars through their assembly lines. The tags tell the computers what the next steps in the automated assembly are at every production stage.
However, there are still some differences that lie in between the RFID system and that of the bar code. RFID removes the need for reading within line of sight, which is needed by the bar code system. And in comparison to the bar code system, RFID can do scanning at a greater distance: active RFID systems typically operate in the ultra-high frequency (UHF) band and offer a range of up to 100 meters. The absence of any physical contact in RFID would mean that the readers will no longer be required to undergo a wear and tear process, and it also applies to those tags that are being used for both reading as well as writing data.
Like the bar-code, RFID has its limitations when the supply chain goes global.
Enter the Global Positioning System to tell the user exactly where the product is. The Global Positioning System (GPS) is a US-owned, space-based satellite navigation system that provides users with positioning, navigation, and timing (PNT) services in all weather conditions, anywhere on or near the earth where there is an unobstructed line of sight to four or more GPS satellites. The system provides critical capabilities to military, civil, and commercial users around the world.
The United States government created the system, maintains it, and makes it freely accessible to anyone with a GPS receiver. The system consists of three segments: the space segment, the control segment, and the user segment. The U.S. Air Force develops, maintains, and operates the space and control segments. The space segment consists of a nominal constellation of 24 operating satellites that transmit one-way signals that give the current GPS satellite position and time. The control segment consists of worldwide monitor and control stations that maintain the satellites in their proper orbits through occasional command maneuvers, and adjust the satellite clocks. It tracks the GPS satellites, uploads updated navigational data, and maintains health and status of the satellite constellation.
The user segment consists of the GPS receiver equipment, which receives the signals from the GPS satellites and uses the transmitted information to calculate the user's three-dimensional position and time. North American manufacturers could have been somewhat assuage during the recent west coast dock strike where GPS was part of the supply chain, because they would have known exactly where their container full of required parts was off the west coast, and said container could be tracked when it eventually moved into a port.
Another important technology for the global supply chain is RTLS (Real-Time Locating System). RTLS are used to automatically identify and track the location of objects or people in real time, usually within a building or other contained area. Wireless RTLS tags are attached to objects, and in most RTLS, fixed reference points receive wireless signals from tags to determine their location. Examples of RTLS include tracking automobiles through an assembly line, and locating pallets of merchandise in a warehouse. RTLS are a form of local positioning system, and do not usually refer to GPS, and location information usually does not include speed, direction, or spatial orientation.
There are two primary RTLS design elements, and they are locating at choke points and locating in relative coordinates. The former is where short range ID signals from a moving tag are received by a single fixed reader in a sensory network, thus indicating the location coincidence of reader and tag. Accuracy is usually defined by the sphere spanned with the reach of the choke point transmitter or receiver. This is not that different from the basic concept of RFID; i.e. a tag passing by a reader.
The latter design element is when ID signals from a tag are received by a multiplicity of readers in a sensory network, and a position is estimated using one or more locating algorithms, such as trilateration, multilateration, or triangulation. Equivalently, ID signals from several RTLS reference points can be received by a tag, and relayed back to a location processor. Localization with multiple reference points requires that distances between reference points in the sensory network be known in order to precisely locate a tag, and the determination of distances is called ranging.
There is a wide variety of system concepts and designs to provide RTLS, and the more popular ones include:
- RFID (active, active-infrared hybrid, semi-active, passive)
- Infrared (IR)
- Optical locating
- Low-frequency signpost identification
- Radio beacon
- Ultrasound Identification
- Ultrasonic ranging
- Wide-over-narrow band
- Wireless Local Area Network (WLAN, Wi-Fi)
Unfortunately, there is no supplier that provides all these technologies. Supply chain visibility platforms have emerged that include a variety of supply chain applications, like warehouse management and transportation management, as well as supporting technologies. These platforms can help users stitch the automatic identification technologies together in a manner that supports both end to end visibility and specific supply chain tasks.