Wireless means radio in its broadest sense. However, in the early 21st century, wireless refers primarily to the two dominant forms of wireless: cell phones and wireless local area networks (WLANs). This module describes the idea behind the cellular telephone system, how it works, and the primary technologies used in the US and throughout the world. This module also introduces the wireless local area network or WLAN. WLANs are radio-linked computers that are part of a larger network. The wireless links make portability and mobility of computers possible. This module also briefly introduces four common forms of short- range wireless: Bluetooth, ZigBee, ultra wideband (UWB) and RFID.