In part 4 of this volume, we shift our focus away from wired communications to the world of wireless LANs. Instead of encoding messages into electrical or light signals sent along Ethernet cables, wireless devices encode messages into electromagnetic waves that propagate through the air all around us. Compared to wired LANs, wireless LANs present various challenges but also provide a degree of mobility and flexibility that simply isn’t possible when communicating via cables.
Chapter 18 begins this part of the book by introducing wireless LANs, the challenges they present, the characteristics and behaviors of electromagnetic waves, the radio frequency bands used for wireless LANs, and how devices connect to form wireless LANs. In chapter 19, we move on to examine wireless LAN architectures, focusing on autonomous wireless access points (APs)—standalone APs managed on a one-by-one basis—and lightweight APs (LWAPs), which are centrally controlled via a wireless LAN controller (WLC); the latter option is the option of choice for most enterprises.