“Internet of Things” Tutorial

The technologies that make up the “Internet of Things” provide the capability to collect data in a completely automated fashion, on a continuous basis not possible when collecting it through human intervention. This is because these technologies can collect data 7 days a week 24 hours a day with 100 percent accuracy.

Once an asset serial number has been assigned to a bar-code, RFID tag or to a GPS unit, data about the location or environmental conditions surrounding that asset can be collected, matching the bar-code, RFID tag or GPS identification code to the serial number in an automated fashion. This is accomplished by storing this information in a database and simply matching the numbers when the tag is read. Data collected can be used to improve operational efficiency as well as customer service.

By electronically identifying your equipment & tools, a specific piece of equipment can be instantly identified, as well as where is it located, if has it been returned to the yard and when it was returned to the yard. Whether it is available for re-use is also visible because all maintenance information is available electronically at your fingertips. This will include when it was last maintained/inspected, who did the work, how long it took and the certifications of the technician that did the work. You’ll also have electronic access to compliance documents for health and safety inspectors.

Companies no longer must depend on a qualified engineer with the aid of a wire brush and solvent to clean the id plate to correctly identify equipment. By attaching these electronic identifiers to major assets and linking these identifiers to the records held in the enterprise systems, simply ‘reading’ the data contained on the identifier identifies it to the handheld computer. This allows for automatic validation with your enterprise systems, elimination of human error and insurance that accurate data is being fed to your enterprise systems.

Best Usages for RFID

Tracking of people, assets or consumables – RFID is now widely used for tracking people, assets and consumables. People tracking solutions vary from passive ID-tag based solutions that might use LF or HF-based proximity cards to UHF asset tracking solutions used to tie people to assets via ID-tags and portals to full active solutions using real time location systems that can track the precise location of every person and asset in a facility at all times.

Where bar codes are not sufficient – Barcodes are insufficient where line of sight on the barcode cannot be adequately achieved, preventing a successful read of the tag. Barcodes are also insufficient when the tagged device is to be painted during a maintenance cycle. When this occurs, the barcode can no longer be read. Both of these problems can be solved by using RFID.

Where GPS is too expensive – GPS can be used to track people, assets or consumables when they need to be tracked outside the range of even an active RFID reader. These units typically combine a GPS unit with a cell phone, satellite phone or both. On devices combining both, the cell phone will be used if it is within range of a tower. If communications cannot be established with a cell tower then the satellite phone will be used to relay position.

Targeted Goals for Utilization

Create competitive advantage – can these technologies provide us with capabilities that will extend the services we provide our clients beyond what our competitors provide?

Reduce operating costs – can we use the information we collect using these technologies to provide richer metrics and enhance our operational capabilities?

Increase revenues – are there new revenue streams we can gain access to by coupling these technologies to our current product or services offerings?

Meet regulatory requirements – are there regulatory requirements that can be more easily met by using these technologies?

Understanding the Options

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Bar CodesPassive RFIDActive RFIDWANHardened Mobile Devices
Direct Parts MarkingLFHFUHFWi-FiISOUWBCellSatPassive RFID with CellActive RFID with Cell
Middleware – ALE Standard
Software for Mobile Devices

RFID versus Bar Code

Barcodes are typically the first choice for auto-ID technologies because they are the cheapest to deploy. As mentioned above, they have limitations that can force the use of various types of RFID or GPS.

RFID – Active vs. Passive

The vast majority of RFID tags or transponders (the terms are often used interchangeably) use a silicon microchip to store a unique serial number and sometimes additional information. There are two broad categories of RFID systems—passive and active systems. Passive RFID tags do not have a transmitter; they simply reflect back energy (radio waves) coming from the reader antenna. Active tags have their own transmitter and a power source, usually—but not always—a battery (active tags could draw energy from the sun or other sources). They broadcast a signal to transmit the information stored on the microchip. (There are also semi-passive and battery-assisted RFID tags, which are suitable for specific applications.)

Passive RFID Systems

Passive RFID tags have no power source and no transmitter. They are cheaper than active tags (20 cents to 40 cents) and require no maintenance, which is why retailers and manufacturers are looking to use passive tags in their supply chains. They have a much shorter read range than active tags (a few inches to 30 feet).

A passive RFID transponder consists of a microchip attached to an antenna. The transponder can be packaged in many different ways. It can be mounted on a substrate to create a tag, or sandwiched between an adhesive layer and a paper label to create a printable RFID label, or smart label. Transponders can also be embedded in a plastic card, a key fob, the walls of a plastic container, and special packaging to resist heat, cold or harsh cleaning chemicals. The form factor used depends on the application, but packaging the transponder adds significantly to the cost. Passive tags can operate at low frequency, high frequency and ultra-high frequency. Low-frequency systems generally operate at 124 kHz, 125 kHz or 135 kHz. High-frequency systems use 13.56 MHz, and ultra-high frequency systems use a band anywhere from 860 MHz to 960 MHz Some systems also use 2.45 GHz and other areas of the radio spectrum.

Radio waves behave differently at each of these frequencies, which means the different frequencies are suitable for different applications. We’ll explain a little bit about the different frequencies, but it’s useful to think of low frequency waves as the waves that reach your radio. They can penetrate walls well, but can’t go through metal. Low-frequency tags are ideal for applications where the tag needs to be read through material or water at close range (more about read range in a minute).

As you increase the frequency of radio waves they start to behave more like light. They can’t penetrate materials as well and tend to bounce off many objects. Waves in the UHF band are also absorbed by water. The big challenge facing companies using UHF systems is being able to read RFID tags on cases in the center of a pallet, or on materials made of metal or water.

Inductive vs. Propagation Coupling

So why are companies eager to use UHF passive systems in the supply chain, rather than low-frequency and high-frequency systems? One reason is some vendors in the UHF market have offered simple, low cost tags. Another reason is read range. Companies need to be able to read tags from at least 10 feet (3.3 meters) for RFID to be useful in a warehouse. That’s because there is no way to read a tag on a pallet going through a dock door from less than 10 feet. At closer distances, the reader begins to interfere with the normal operation of forklifts and other equipment. Low-frequency tags can usually be read from within 12 inches (0.33 meter). High frequency tags can be read from up to 3 feet (1 meter), and UHF tags can be read from 10 feet or more.

Read range is determined by many factors, but one of the most important is the method passive tags use to transmit data to the reader. Low- and high-frequency tags use inductive coupling. Essentially, a coil in the reader antenna and a coil in the tag antenna form an electromagnetic field. The tag draws power from the field, uses the power to run the circuitry on the chip and then changes the electric load on the antenna. The reader antenna senses the change in the magnetic field and converts these changes into the ones and zeros that computers understand. Because the coil in the tag antenna and the coil in the reader antenna must form a magnetic field, the tag must be fairly close to the reader antenna, which limits the read range of these systems. Passive UHF systems use propagation coupling. A reader antenna emits electromagnetic energy (radio waves). No electromagnetic field is formed. Instead, the tag gathers energy from the reader antenna, and the microchip uses the energy to change the load on the antenna and reflect back an altered signal. This is called backscatter.

UHF tags can communicate ones and zeroes in three different ways. They can increase the amplitude of the wave coming back (amplitude shift keying), shift the wave so it’s out of phase (phase shift keying) or change the frequency (frequency shift keying). The reader picks up the signal and converts the altered wave into a one or a zero. That information is then passed on to a computer that converts the binary data into a serial number or the data stored on the tag.

Factors that Affect Performance

It’s not necessary to understand the intricacies of the communication methods used, but end users do need to understand the basic characteristics of the different systems and what affects their performance. Because low- and high-frequency systems use inductive coupling, the size of the reader field is smaller and can be more easily controlled. Ultra-high frequency systems that use propagation coupling are harder to control, because energy is sent over long distances. The waves can bounce off surfaces and reach tags you never expected them to reach; you might even read tags you don’t want to read.

Low- and high-frequency systems also work better than UHF systems around metal and water. The radio waves don’t bounce off metal and cause false reads. And they are better able to penetrate water; UHF radio waves are absorbed by water.

In fact, the problem with reading tags reliably is mainly an issue with UHF systems and propagation coupling is a common problem. With propagation coupling, the antenna is tuned to receive waves of a particular frequency. When an antenna is placed on an object or product packaging that is not “RF friendly,” the antenna can be detuned, making it difficult for the tag to receive enough energy to reflect back a signal. There are several ways to deal with this issue. Products with a lot of water and metal are particularly challenging to tag, and some antennas can be specially designed to be in tune when close to water or to couple with the metal to improve the ability to read the tag. Another way is to create an air gap between the tag and the object. In the case of metal, an air gap can increase performance if done correctly, because waves will reflect off the metal and provide more power to the tag.

Signal Attenuation

Attenuation in RFID usually refers to the reduction in energy emitted by the reader or in the energy reflected back by the tag. If less energy is able to reach the tag, then the tag must be closer to the reader to be read. The energy emitted by the reader naturally decreases with distance; the rate of decrease is proportional to the inverse square of the distance. Passive UHF RFID tags (those with no batteries) reflect back a signal at very low power levels. A tag’s reflected signal decreases as the inverse fourth power of the distance between tag and reader. In other words, the signal emitted by the reader attenuates natural with distance, and the signal reflected by a passive tag attenuates at a much faster rate.

Signal attenuation can also be caused by the way a system is installed or external factors, such as the items tagged. Many readers have one or more external antennas that emit radio waves. These are connected to the reader by coaxial cables. As the energy travels from the reader, through the cable, to the reader antenna, the signal attenuates, so placing reader antennas too far from the reader can cause poor performance. Water, carbon and other materials absorb UHF energy, so products with high water content, such as fruit and soft drinks, or products made of carbon, such as batteries, can attenuate the signal reaching the tags on these products.

Electromagnetic Interference

EMI is essentially electronic noise that makes it harder to get a clear signal back from the UHF tag. It can be caused by a wide variety of machines. Motors emit EMI and may need to be shielded to prevent interference with RFID systems. Conveyors with nylon belts cause interference, as do most robots on manufacturing lines.

Interference can also be caused by other RF-based systems operating in a warehouse or other areas where RFID is used. For instance, many older wireless local area networks use the UHF frequency band. These interfere with UHF RFID systems and need to be upgraded to the 802.11 standard. Cordless phones, wireless computer terminals and other devices can also interfere with RFID systems.

Active RFID Systems and RTLS

Active tags are used on large assets, such as cargo containers, rail cars and large reusable containers, which need to be tracked over long distances (in a distribution yard, for example). They usually operate at 455 MHz, 2.45 GHz, or 5.8 GHz, and they typically have a read range of 60 feet to 300 feet (20 meters to 100 meters).

Broadly speaking, there are two types of active tags: transponders and beacons. Active transponders are woken up when they receive a signal from a reader. These are used in toll payment collection, checkpoint control and other systems. When a car with an active transponder approaches a tollbooth, a reader at the booth sends out a signal that wakes up the transponder on the car windshield. The transponder then broadcasts its unique ID to the reader. Transponders conserve battery life by having the tag broadcast its signal only when it is within range of a reader.

Beacons are used in most real-time locating systems (RTLS), where the precise location of an asset needs to be tracked. In an RTLS, a beacon emits a signal with its unique identifier at pre-set intervals (it could be every three seconds or once a day, depending on how important it is to know the location of an asset at a particular moment in time). The beacon’s signal is picked up by at least three reader antennas positioned around the perimeter of the area where assets are being tracked. RTLS are usually used outside, say, in a distribution yard, but automakers use the systems in large manufacturing facilities to track parts bins. Active tags have a read range of up to 300 feet (100 meters) and can be read reliably because they broadcast a signal to the reader (some systems can be affected by rain). Their cost varies, depending on the amount of memory, the battery life required, whether the tag includes an on-board temperature sensor or other sensors, and the ruggedness required. A thicker, more durable plastic housing will increase the cost.

Combining Passive and Active RFID with GPS

The goal of using RFID in open supply chains is to gain “visibility”—that is to be able to “see” where your products are in real time. Visibility, however, is often lost once products are shipped. It’s possible to combine active and passive systems to record which container goods are in and when a container has left a distribution yard on a truck. And with GPS technology, it’s possible to track goods even while in transit. (This kind of system is expensive to implement today and is usually used only when a company is looking to reduce theft in the supply chain.)

The U.S. Department of Defense plans to combine passive RFID tagging of pallets, cases and some high-value items with the active tagging system it already uses to track many containers being shipped to bases and units overseas. The DOD will scan the passive tags on cases of meals ready to eat and other items and associate the EPCs on those cases with a pallet tag. As pallets are loaded onto a container, the case and pallet tag information will be written to an active tag on the container.

A test validated the concept. When a truck left a DOD depot, the active tag on the container was read and the fact that it left was uploaded to the military’s Total Asset Visibility system, a global database for tracking goods. When the truck arrived at a train station, airport or port, the tag was read again and its location updated. Readers at ports, airports and depots have been installed overseas to give the DOD better visibility.

GPS transmitters on trucks can provide real-time location of trucks on the road. The benefit of such a system is the company can insure that high-value goods are not diverted in transit. In the future, a supply chain manager might be able to dynamically manage deliveries. For example, a potential out-of-stock situation could be averted by rerouting a truck to a store dangerously low on a given item.

It’s clear that RFID has the potential to dramatically improve supply chain efficiencies, but the same technology can be used for many other applications, from securing buildings and ensuring the safety of workers to improving asset utilization and reducing manufacturing errors.
Source: RFID Journal

Passive Frequencies and Characteristics

Frequency refers to the size of the radio waves used to communicate between the RFID system components. It is generally safe to assume that a higher frequency equates to a faster data transfer rate and longer read ranges, but also more sensitivity to environmental factors such as liquid and metal that can interfere with radio waves. RFID systems currently operate in the Low Frequency (LF), High Frequency (HF) and Ultrahigh Frequency (UHF) bands.

Each frequency has advantages and disadvantages relative to its capabilities. Generally a lower frequency means a lower read range and slower data read rate, but increased capabilities for reading near or on metal or liquid surfaces.

No single frequency is ideal for all applications, even within a single industry. Just as separate bar code symbologies are used at different levels of consumer goods packaging, from U.P.C./EAN symbols at the item level to Code 128 and two-dimensional symbols on cases and pallets, RFID tags of different frequencies and functionality will be used together within overall supply chain operations.

Low-Frequency (LF)

Low-frequency RFID systems are typically 125 KHz, though there are systems operating at 134 KHz as well. This frequency band provides a shorter read range (< 0.5m or 1.5 ft) and slower read speed than the higher frequencies. LF RFID systems have the strongest ability to read tags on objects with high water or metal content compared to any of the higher frequencies. LF systems tend to be less sensitive to interference than higher frequency options.

Typical low-frequency RFID applications are access control, animal tracking, vehicle immobilizers, healthcare applications, product authentication and various point-of-sale applications (such as Mobil/Exxon SpeedPass). The LF spectrum is not considered a truly global application because of slight differences in frequency and power levels throughout the world.

High-Frequency (HF)

High-frequency RFID systems operate at 13.56 MHz, and feature a greater read-range and higher-read speed than LF systems. Also, the price of the tags is among the lowest of all RFID tags. Typical read range is less than 1 meter (3 feet), and the ability to read tags on objects with high water or metal content is not as good as LF systems but stronger than UHF systems.

Applications include smart cards and smart shelves for item level tracking, and are also currently used to track library books, healthcare patients, product authentication and airline baggage. Another common application is maintenance data logging for sensitive equipment that needs regular checking such as fire suppression systems. There are several standards concerning HF systems, including the ISO 15693 standard used for tracking items.

Ultrahigh Frequency (UHF)

Ultrahigh frequency RFID utilizes the 860 to 930MHz band – typically 868 MHz in Europe and 915 MHz in North America. UHF tags typically cost about the same as HF tags. Read range is up to 3m (9.5 ft) and the data transfer rate is faster than HF systems, though still lower than Microwave based RFID systems, which are discussed next.

One drawback to UHF systems is a limited ability to read tags on objects with or surrounded by high water or metal content. This is typically the frequency recommended for distribution and logistics applications and is the basis for the Electronic Product Code (EPC) standard driven through the Auto-ID Center. Of course, the EPC standard is the focus of Wal-Mart and the Department of Defense in the United States.

The primary rationale for utilizing this frequency in the supply chain is the greater read range it offers over the other frequency ranges. However, UHF is also widely used for electronic toll collection systems on highways, manufacturing applications and parking lot access based on the greater range provided by the frequency.

The North American market operates at or near 915 MHz, while much of Western Europe is at the low end of the spectrum, and several Asian companies recently opened the higher end of the spectrum to RFID usage.

Microwave

The final frequency option is the microwave band, either 2.45GHz or 5.8GHz. Though microwave based RFID systems offer the highest data read rates, they are the most expensive systems and have a limited read range of up to 1m (3 ft). Additionally, microwave based systems are not able to penetrate objects with high water or metal content which makes it unsuitable for many applications. At this time, microwave is constrained to specialized applications such as tracking airline baggage or electronic toll collection. Though it could be used for some supply chain applications with high data content, the inability to penetrate water or metal combined with the higher cost will limit its deployments in this realm.

Business Use Scenarios

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Frequency BandDescriptionOperating RangeApplicationsBenefitsDrawbacks
125KHz to 134 KHzLow Frequency< .5M or 1.5ft.
  • Access Control
  • Animal Tracking
  • Vehicle immobilizers
  • Product Authentication
  • POS applications
Works well around water and metal products.Short read range and slower read rates
13.56 MHzHigh Frequency< 1M or 3ft.
  • Smart Cards
  • Smart shelve tags for item level tracking
  • Library Books
  • Airline Baggage
  • Maintenance data logging
Low cost of tagsHigher read rate than LF
860 MHz to 930MHzUltrahigh Frequency (UHF)3m or 9ft.
  • Pallet tracking
  • Carton Tracking
  • Electronic toll
    collection
  • Parking lot access
EPC standard build standard built around this frequencyDoes not work well around items of high water or metal content
2.4GHzMicrowave1m or3 ft.
  • Airline Baggage
  • Electronic toll collection
Fastest read ratesMost expensive

Source: ScanSource

RFID Tags and Readers

RFID tags and readers are generally selected for the specific engagement requirements. Selection of tags is generally determined based on required read range, ability to read the tag from angles and the form factor. The form factor is the materials encasing the tag. Form factors can range from the simplest which may consist of a smart label to hardened cases that are extremely resistant to heat, UV, chemical and impact exposure. RFID readers are typically chosen to complement the tag type and will also require form factor choices.

GPS with Cell vs. Satellite Communications

GPS can be used to track people, assets or consumables when they need to be tracked outside the range of even an active RFID reader. These units typically combine a GPS unit with a cell phone, satellite phone or both. On devices combining both, the cell phone will be used if it is within range of a tower. If communications cannot be established with a cell tower then the satellite phone will be used to relay position.

Geo-Fencing

Geo-fencing is typically used to define a specific geographical area in electronic form. When a tagged item is moved outside of a Geo-fence, alarms may be triggered to alert security personnel to a potential theft.

Proactive Alarms and Alerts

As previously stated for Geo-fencing, alarms and alerts are frequently tied to RFID or GPS installations where the tracking of people or equipment is critical to ensuring security.