ABSTRACT
This chapter describes the communication methods used to transfer information from the interrogator to the transponder and from the transponder to the interrogator. It explores the most common approaches to the communication between these elements of the radiofrequency identification system using specific systems as general examples. The chapter describes the different air communication protocols followed by the study of the elements that make up the forward and the return communications link. It talks about the different modes of operation available to transponders. The chapter also describes the different arbitration methods and the anticollision procedures that allow effective communication when there is more than a single transponder in the radiofrequency field. In addition, the link between transponder and interrogator operates synchronously, and because the interrogator controls the speed and modulation ticks, the resulting transmission has a higher signal-to-noise ratio than an asynchronous communication.
