An introduction to Digital Track & Trace technologies in Supply Chains

Before you ride the hype wagon again….

Yes, it will be so sweet to have an IoT enabled network but have you given a thought to the fact that many of the “visibility” and “traceability” aspects being touted as benefits from IoT may already be available in form of other technologies ? Do you know that many forms of  Automatic identification (auto-ID) technologies have been available for quiet some time and are very mature ? Another example of why you should think about the non technology aspects as a barrier to many issues in the Supply Chain.

Coming back to auto-ID technologies, they have the capability to track and trace objects, products, assets, and individuals through-out the value chain by capturing and transferring data with limited or no human intervention. They can provide the essential information (e.g., location, vibration, temperature, humidity, arriving time, speed, and vehicle status) in an automated and timely manner which allows early decisions and eliminates error-prone manual activities . While there are several auto-ID technologies involved in automated tracking, the most commonly used technologies at various points in Supply Chains are:

  • Barcodes
  • Radio Frequency Identification (RFID)
  • Real-time Locating Systems (RTLS), and
  • Global positioning systems (GPS)

Let us review the above mentioned technologies in some detail in this post.

1. Barcode:

Barcodes are printed digital codes which consist of black parallel lines (bars) or small modules (squares) arranged on a white background. A barcode can be read by a barcode reader which uses a laser beam as well as a mobile device with a barcode reader software installed. While traditional barcodes with parallel lines have a low data capacity, 2D barcodes with modules (e.g., quick response (QR) code) can store up to 7089 characters. Barcode technology is inexpensive and the most commonly used auto-ID technology in the world. However, the line-of sight reading requirement, poor data security, deterioration due to dirt and bending in difficult environments, and read-only capability are the main weaknesses of the technology.

2. Radio Frequency: Identification (RFID):

An RFID system, which uses radio waves for data transfer, typically consists of the  following elements:

• A tag with a chip that can store the unique identification number and information of the item to which it is attached.
• A reader with antennas to simultaneously communicate with multiple tags within the range of the antennas. The communication can be either unidirectional or bidirectional.
• Application software with a database that processes and integrates the collected information.

Unlike barcodes, which must be oriented towards the scanner for reading, RFID tags can be read without line-of sight requirements as long as they are within range of a reader. Hence, tagged objects can be easily tracked in the supply chain without human involvement. Also, RFID tags can hold greater amounts of data which can be transmitted fast, rewritten many times, and encrypted. Other advantages of RFID tags are that they are reusable and more durable to temperature and other environmental factors.

Along with such benefits, the high investment cost is the main drawback of RFID in many applications. Other concerns regarding material types (e.g., metal and liquid), inference, bulk reading reliability, and lacking standardization also limit the applications. There are different kinds of RFID tags available with different configurations, cost implications, and performance trade-offs. However, RFID systems can be broadly categorized as:

  • passive
  • semi-passive
  • active

A passive tag, the simplest form of RFID tag, does not have an internal power source.  his type of tag converts radio frequency energy coming from the reader antenna into  electrical energy to send back a signal to the reader. Passive RFID systems can operate in the low frequency (LF), high frequency (HF), or ultra-high frequency (UHF) radio bands. They typically have short read ranges (a few centimeters for LF and up to 12 m for UHF) and can hold a little more information than barcodes. However, they are cheaper,  lighter, smaller, and easier to print than other RFID types. Because they do not have their own energy source, sensors cannot be attached on passive RFID tags.

A semi-passive RFID tag is a battery assisted passive tag that contains an integrated  power source to supply energy to the chip but relies on the reader’s energy to send a signal. Semi-passive tags can have longer read ranges and some of them can support sensors, but they are more expensive and bigger than passive tags.

An active RFID tag contains its own transmitter and a power source which can be a battery, or a solar panel to draw energy form the light. This type of tag can broadcast a signal independently to a reader. Active RFID systems usually operate in the UHF radio bands and have substantially larger ranges (up to 100 m). They can transmit their location and other important information. The cost of an active tag can vary from a few dollars to a hundred dollars, depending on the reading range, battery life, durability, and other capabilities required. Readers also are more expensive than the ones used for passive systems.

Active tags are generally used on expensive and large assets (e.g., trucks, containers, rail cars, animals, medical equipment). The on-board power source can also support sensor operations which greatly improves the utility of the RFID systems, especially for cold chain logistics of temperature sensitive products like fruits, fish, drugs, and vaccines .

Transponders and beacons are the two main types of active tags. Transponders are powered on when they receive a signal from a reader. For example, they are used for vehicle identification in secured gates. When a car with a transponder approaches a gate, the transponder on the car wakes up with the signal of the reader at the gate and then sends its unique ID to the reader. Transponders conserve battery life as they send signal only when they are within the range of a reader. Beacons, on the other hand, continuously broadcast signals at pre-set intervals such as every few seconds or once a day.

3. Real-time Locating Systems (RTLS):

Real-time Locating Systems (RTLS) provide the location of objects or people in real-time by continuously tracking them within a building or other closed area. The information regarding the tracked object can include the location, speed, temperature, and other specified information. Examples of RTLS include tracking patients in a hospital, tracking automobiles through an assembly line, or locating lift trucks in a warehouse. Current RTLS are based on wireless technologies such as RFID, infrared, ultrasound, and wireless sensor networks . Among different RFID types, beacons (active systems) are often used in RTLS. The location of the tagged object can be identified by reading the signal of the tag by at least three antennas. Passive systems can provide low-cost RTLS solutions.

Tags attached to the surface of objects or people transmit a unique ultrasound signal to communicate their locations to the microphones places around the room being monitored. Similar to infrared waves, ultrasound signals provide accurate results with careful positioning of several receivers (microphones), and they are contained by walls. Wireless sensor networks (WSN) consist of small and low-powered autonomous computing nodes which are spatially distributed for monitoring and recording conditions at diverse locations. Every computing node is equipped with a transducer, microcomputer, radio frequency transceiver, power source; and a sensor which detects ight, temperature, humidity, sound, pressure, vibration, pollutant levels, or other physical conditions.

The collected data are transmitted among sensor nodes by hopping, and finally reach the gateway for connection to the internet. WSN can be designed in different network topologies including star, where each node connects directly to a gateway; cluster tree, where each node connects to a node in higher tree and then to a gateway; mesh, where nodes can connect to multiple nodes and the message goes through the most reliable path available; and ring, where every node is connected to two neighbors.

4. Global positioning systems (GPS):

GPS allow items to be remotely tracked anywhere on Earth at real-time using satellite  navigation system. GPS are appropriate to track vehicles and shipping containers in logistics. A GPS receiver can determine its location in latitude and longitude by  communicating to at least three satellites and calculating the distance to each . The location information is then transferred to a server through a wireless page/voice network . A GPS receiver can operate worldwide for several years.

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