ABSTRACT

The internet of things has sometimes been referred to as the digitization of the physical world. A device embedded with a sensor and/or actuator, connected to the internet that shares its information with other devices and hosts, with the potential to act on this information based upon some rules and intelligence. This chapter provides an overview of the physical and link layer technologies, but the higher layers will be mentioned where it is appropriate. The physical layer defines the hardware aspects of the communication link, such as the modulation method, voltage levels, and physical medium. The link layer provides several services, typically implemented with a combination of hardware and software. If the physical medium is shared by multiple users, such as wireless communication on a certain frequency band, then orderly access to the medium must be controlled so that users don't interfere with each.