A new book about deploying and securing RFID does a great job of explaining RFID technology, but what really impressed me was how well the authors explain digital RF propagation theory.
The book, How to Cheat at Deploying and Securing RFID, written by Frank Thornton and Paul Sanghera, does a great job of explaining radio-frequency identification (RFID). RFID technology we all know is an identification method based on the storage and retrieval of data using devices called RFID tags. Since RFID is a new wireless technology, many see the need to evaluate possible security concerns, which is also a major part of this book.
What really impressed me about this book was not the information about RFID technology per se, but how well the authors explain digital RF propagation theory. You do not have to take my word either; Mobile Handset DesignLine has published select sections from the book on their Web site. The first article, "The Physics of RFID" gives a great explanation of digital modulation. I like how the authors use human audio communications as an example of modulation:
"First, understand that the information is communicated through changes (such as vibrations) in the carrier signal. The carrier signal itself is a constant signal unchanging in frequency and voltage—for example, a sine wave. It represents no information. As an analogy, I would not convey much information if I merely produced a constant sound out of my mouth, such as:
To convey some information, I would need to speak different sentences and different words in a sentence. In radio frequency communication, the information is encoded into the carrier signal using a technique called modulation, which means variation or change. You take the data signal that represent the information and impress it on a constant radio wave called a carrier. The data signal, as a result, varies (or modulates) the carrier wave. Once transmitted through an antenna, the two go together dancing over the air in the form of a modulated signal."
A second article, "The Physics of RFID-Part II" eloquently explains all the nuances required for a RF link to work correctly. For example, the following excerpt illustrates what a voltage standing wave ratio (VSWR) is:
"A standing wave, also called a stationary wave, is a result of interference between two waves moving in the opposite direction. In an RFID system, this situation can arise due to the impedance mismatch along the transmission line from source to antenna transmitter. The impedance mismatch will result in reflecting part of the energy from the antenna back to the source, and the forward wave and the reflected wave will interfere with each other. Two cases for this interference are constructive and destructive, respectively:
Constructive interference: This is the case when the crests of one wave coincide with the crests of the other wave, and therefore the amplitude of the resultant wave is the sum of the amplitudes of the interfering waves:
Destructive interference: This is the case when the crests of one wave line up with the troughs of the other wave, and therefore the amplitude of the resultant wave will be the difference of the amplitudes of the interfering waves:"
RFID technology will become pervasive throughout the business world because of its ability to easily track just about anything. IT personnel will be at the forefront of implementing this technology and getting the tracking information where it needs to go. For those wireless and wired network administrators wanting to learn about RFID, this book does an excellent job of introducing and explaining the technology. Even still, that is not what impressed me the most about the book. I was pleasantly surprised that the book took time to edify the principles of digital RF propagation and did a good job of it.
It appears that Mobile Handset DesignLine is going to continue this series as "The Physics of RFID-Part III is now available on their website.