Cost
High volume Tags are currently 25 cents each with the potential to continue to drop per the experience curve. High volume bar codes are less then a penny. This is a clear advantage for BC unless you expand cost to be fully loaded. In this scenario, the labor savings from items like physical counts, etc. give RFID greater feasibility.
Reusable
RFID - Yes
BC - No
What jumps out from this comparison is RFID's capability to greatly amplify the benefits received from traditional bar coding. By eliminating the manual task of reading a bar code, RFID automates data entry. This permits new ways of processing items, events, or transactions.
RFID is based on a chain of scientific discoveries from some of the most important intellectual pioneers like:
- Michael Faraday, in 1846, identified that both light and radio waves are part of electromagnetic energy.
- James Maxwell, in 1864, propounded his theory that electric and magnetic energy travel in transverse waves at the speed of light.
- Heinrich Hertz, in 1887, proved Maxwell's theory and showed that radio waves may be reflected, refracted, and polarized like light.
- Guglielmo Marconi demonstrated long distance transmission of radio waves.
Radio Frequency Identification is a way of storing and retrieving data through electromagnetic transmission to an RF compatible electronic circuit. To understand RFID we must discuss the science of Radio.
All radio transmissions use electromagnetic waves that are created when alternating currents flow through an antenna. The word electromagnetic is the concatenation of electric and magnetic and implies two types of linked phenomenon make up the radio wave. We cannot directly see, taste, touch, or hear electromagnetic waves, so it’s not surprising that their operation is mystifying.
Let’s try and understand this better.
First, electric fields are created by differences in voltage. A simple relationship governs this: the higher the voltage, the stronger the field . Second, magnetic fields are created when current flows. Again, a simple relationship governs this: the greater the current, the stronger the magnetic field. So let’s quickly recap: Electric fields exist even when current is not flowing whereas Magnetic fields only exist when current is flowing. When the two exist together, they are commonly referred to as Electromagnetic Fields (EMF).
EMF is present everywhere in our lives but they are invisible to the eye. Natural sources like the earth's magnetic field cause a compass needle to orient in a North-South direction. Besides these natural sources, the electromagnetic spectrum also includes fields generated by human-made sources such as X-rays and garage door openers. The electricity in our homes has associated low frequency electromagnetic waves. Various other kinds of higher frequency electromagnetic waves are used for radio transmissions in TV, radio, cellular and RFID, to name a few.
In all these applications, the power and variance of the electromagnetic fields are vital to their intended operation. An important concept, which defines EMF, is frequency. Let’s imagine an ocean with a series of very regular waves. The frequency simply describes the number of waves per second that crest at a static point of measurement. Geeks describe this as the oscillations or cycles per second. The term wavelength describes the distance between the crest of one wave and the next. Hence, wavelength and frequency are inseparably intertwined: the higher the frequency, the shorter the wavelength. To translate this to radio waves imagine the ocean waves traveling at an enormous speed, the speed of light, which is 186,000 miles per second.
Another simple analogy should help reinforce the concept. Tie a long rope to a door handle and keep hold of the free end. Moving it up and then down slowly will generate a single big wave; more rapid motion will generate a whole series of smaller waves. We know the length of the rope is constant. As you create more waves you are increasing the frequency while making them shorter in distance (wavelength).
Frequency is commonly known as Hertz in honor of radio pioneer, Heinrich Hertz. One cycle per second is 1 Hertz. The frequency of oscillations ranges from 1 Hertz to infinity and this entire range is known as the Frequency Spectrum. Common units are kiloHertz (which is one thousand Hertz, 1 kHz), megaHertz (one million Hertz, 1 MHz), gigaHertz (one billion Hertz, 1 GHz) or teraHertz (one trillion Hertz, 1 THz).
Frequency Spectrum is viewed as an important resource. It is co-ordinated with legal and political governing bodies generating a plethora of complicated rules and regulations. RFID has specific frequencies for its use. Currently they are:
LF (low frequency): 125kHz, 134 kHz
HF (high frequency): 13.56 MHz
UHF (ultra high frequency): 868 MHz- Europe, 902 to 928 MHz - USA
Microwave: 2.45 GHz  Antenna & Wave Propagation
The EMF are generated and received by the antenna. The antenna is designed to radiate energy out into free space and collect radio energy from space. It is important to recognize that in doing this job the antenna is the most important part of the radio system – without it the system is dead. Another important fact is the antenna system is common to both the transmitter and the receiver; any change in the antenna affects both transmission and reception.
We have learned that the antenna changes radio energy from the transmission line into radiated energy and vice versa. What is remarkable is the efficiency with which an antenna does its job. A light bulb is about 20% efficient in changing electrical energy into light whereas the antenna is nearly 100%. We may break down the antenna’s operation into two fundamental modes of wireless communications:
- Near Field Communications aka close proximity electromagnetic aka inductive coupling
- Far Field Communications aka propagating electromagnetic waves
In either mode antennas have optimal sizes that relate to the frequency of the signal. Basically, the higher frequencies require smaller antennas due to their shorter wavelengths.
Because the sizes of wavelengths vary, radio signals propagate differently through free space. Some are well suited to short ranges while others are good for transmissions involving very long distances. Typically, the higher the frequency, the shorter the distance the signal will travel. The strength of the radio signal diminishes rapidly as it moves away from the transmitter antenna.
Far field radiation is distinguished by the fact that the intensity is inversely proportional to the square of the distance. In reality, due to obstructions, absorption, and interference the loss is more severe, approaching the inverse of the 5th or 6th power of the distance. Whereas Near field radiation intensity is inversely proportional to the cube of the distance in the region that is less then 1/6 wavelength from a simple loop antenna. (For additional reference see: Principles of Antenna Theory by Kai Fong Lee page 231 and the ARRL Antenna Book pg 2-8 and TI Literature Number 11-08-26-003)
Obviously, the radio link is extremely complicated and requires considerable engineering to achieve 100% read rates. Keep in mind that the energy level to write a tag is greater than reading; therefore, the write range is shorter than the read range.
Modulation & Handshaking
Once we have the radio- engineering link operational we may consider how it transports information from one location to another. In a sense, the waves are like an endless line of UPS trucks; they are only valuable when they are filled with stuff. The frequency of the radio wave providing the transport is known as the carrier frequency. The information to be carried is mixed with this frequency by a process known as modulation.
Modulation is necessary because the intelligence of the signal, voice, or data, is usually a much lower frequency that it is not effectively radiated into space.
Using what we have learned in this chapter we may now describe a typical transmitting sequence for a generic tag-antenna-reader system. Let’s start with the greeting. When you meet someone, you usually shake their hand. An analogous situation occurs in electronics with a system handshake. The typical handshake for a passive tag is as follows:
- Reader looks for modulation of its radio frequency sine wave to indicate the presence of a tag.
- When a tag’s antenna captures the EMF generated by the reader’s antenna it initiates a process to respond with a data stream encoded in the carrier.
With a successful handshake, the system begins the transmission of information; as follows:
- The tag typically starts clocking its data messages against an output transistor, which is connected across coil inputs. In this case, the RF link behaves like a transformer where the tag is the primary coil and the reader is the secondary coil.
- As the tag’s output transistor shunts the coil, it effectively modulates the carrier to experience a momentarily voltage drop. The pattern of voltage drops corresponds to the information to be uploaded from the tag to the reader.
The reader must detect these small voltage drops, which represent the modulation. This requires a sensitivity that is able to pick up 1/1000 of a change from the original carrier wave’s amplitude as sent by the reader.
SYSTEM TOPOLOGY
RFID is a scalable system. In its minimalist configuration, the micro-topology requires just four sub-systems, as follows:
- Tag
- Reader
- Air Interface
- Computer Communication and Control
The most demanding macro-topology involves pervasive tagging where sophisticated Readers are simultaneously interrogating multiple tags in a dynamic environment. In this scenario, anti collision algorithms are required in addition to data handling processes for large velocity data streams.
Pervasive Tagging with Anti-Collision Algorithms
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FIVE PHASES OF RFID EVOLUTION
The way I see it, there are five phases for the evolution of the RFID revolution to be, as follows:
Driven by early adaptors who are motivated to gain an advantage in executing their business model. Projects in this stage are closed loop dealing with intra-company business practices and require significant NRE (non-recurring engineering) budgets. Integration complexity is minimized in the scope of work. Although, reducing technology risk is a good thing, it comes at the expense of lowering the scope and strategic power to the organization. Think of this phase as putting your toe in the water to test the temperature to see if you want to jump in; however, you have to build the pool first! Placing this bet  is non-trivial and only certain high pay-off applications will be able to justify the ante for this wager.
Second Phase
Scope of work and strategic power to the organization is increased  significantly. Successful projects endorse and apply standards to increase reliability while incurring a reasonable expense for NRE. Downstream benefits of this stage are scalability and repeatability. The RFID landscape is not fully integrated into the enterprise and represents an intra-company island of automation. Data exporting and importing capabilities improve decision making. Customers experience the impact of the volume and velocity of RFID information and realize they need to seriously address the data warehousing issues lurking below the surface. Tags and Readers are the tip of the iceberg while data is the huge mass below.
Industry standards begin to allow for limited plug and play combinations amongst major RFID infrastructure vendors. Clear and proven standards are not available requiring large NRE budgets for a project to succeed.
Third Phase
Benefits increase in a few key areas of RFID. First, plug and play capability amongst dominant vendors is available. This drives down NRE making it feasible for wide scale adoption of RFID technology into the enterprise. Second, integration with ERP and other systems is rapidly growing due to off the shelf modules, which allow systems to talk to each other and harness the RFID information. Third, real time data flow within the enterprise yields improvements in business practices. Consequently, the scope and strategic power of RFID within the organization blossoms.
The Fourth Phase
 In this phase, RFID connectivity moves outside of the enterprise for large scale integration with secure external entities. Again, this is easily done because infrastructure standards are sufficiently homogeneous with adequate touch-points for integration flexibility amongst different corporate applications. Paying heed to the sage advice that time is money ~ RFID connectivity is now streamlined, reliable and offers little risk in terms of project timeframes and budget over-runs. Non-recurring engineering is limited to the air interface for issues like EMI (electromagnetic interference ). All members within this business space are said to be part of a closed user group (CUG), thereby implying that RFID information is not for general public knowledge.
Implementation of the CUG is typically performed in two distinct ways:
The first approach is to increase the number of RFID nodes in the network by sharing raw RFID data within the CUG. In this case, RFID information is expanded from internal enterprise stake-holders to CUG members. When RFID information is shared beyond the traditional corporate border, it grows in value because of its real time access via the WAN (Wide Area Network).
The second approach focuses on niche applications for RFID, which form a vertical integration along a distribution channel, value add chain, or specific product line. Corporate borders are ignored while real time sharing of information amongst members is done via a WAN.
The Fifth Phase
Characterized by pervasive tagging of pallets, cases, cartons and individual items. Ad-hoc applets are prevalent anywhere the tags are present. Intra-company and Inter-company applications flourish. Industry trade-groups exist to maintain global databases for access to the public. This requires infrastructure to create and maintain a universal database and a public WAN (very similar to the 411 directory service offering nation wide telephone numbers for users).
RFID science has grown feature rich with cost reduction. The power of networked RFID nodes is realized and provides attractive ROI. Billionaire rebel Sir Richard Branson invests in a new company aptly titled Virgin RFID thereby proving RFID has safe tagging.
We have achieved Clampitt's Law, simply stated:
"The COST of a TAG is inversely related to the square root of the number of networked READERS while the VALUE of a TAG increases every time a READER is networked."
You may judge the success of a technology by the number of standards created to harness its capability. RFID remains true to this trend!
RFID Standards are being adopted and agreed upon, as follows:
ISO 15693 – Smart Labels
ISO 14443 – Contact less payments
ISO 11784 – Livestock
ISO 18000 - Air interface protocol
UCC and EPCglobal
EPC – Class 0, Class 1, Class 1 - version 2, Class 2
Standards will evolve to ensure the components of an RFID system are plug and play. |
