ELLULAR NETWORKS Wi-Fi networks first became prevalent in homes, where the savings that result from the elimination of running unshielded twisted-pair (UTP) cabling appealed to resi- dential consumers. Companies, too, rely on these networks due to the proliferation of laptops, tablet computers, and mobile employees, as well as improvements in security and capacities. In addition, some mobile carriers are now using Wi-Fi technology to supplement their cellular capacity. Mobile and Wi-Fi Networks The 802.11 Standard, WLAN, and Wi-Fi The designation 802.11 refers to the family of Institute of Electrical and Electron- ics Engineers (IEEE) standards around which most Wireless Local Area Networks (WLANs) are built. Recall that Wi-Fi is short for wireless fidelity. "WLAN" is a generic term applicable to any wireless LAN technology. Because 802.11 is the domi- nant WLAN technology, people use the terms "802.11," "Wi-Fi," and "WLAN" inter- changeably. Table 7-2 lists the commonly installed 802.11 network protocols. Table 7-2 802.11 Wireless Local Area Network (WLAN) Standards Achievable Number of Frequency Standard Top Speed Speed Channels* 802.11a 54Mbps 25Mbps 802.11b 11Mbps 5Mbps 2.4GHz 802.11g 54Mbps 12- to 25Mbps 2.4GHz *The number of channels varies internationally. The 802.11 Standards The standards presented in Table 7-2 refer to the frequencies, speeds, and number of channels in each Wi-Fi standard. Other 802.11 standards that specify capabilities such as security, Quality of Service (QoS), and internetworking with cellular networks are listed in Table 7-5 in the "Appendix" section at the end of this chapter. Wi-Fi i networks in enterprises commonly support all three of the standards. Lower-priced equipment with only 802.11b and 802.11g is also sold to enterprises. Because they are less robust, are less expensive, and support fewer devices, home Wi-Fi networks generally only support 802.11b and 802.11g. The frequency of a signal impacts its range (how far it is able to travel). Signals in lower-frequency bands tr