 WMANs, WLANs, and WPANs over regular data. Examples of applications include transport of audio and video over 802.11 wireless networks, videoconferencing, media stream distribution, enhanced security applications, and mobile and nomadic access applications. The operation of the 802.11e standard is discussed further later in this chapter, in the section "VoWLAN." IEEE 802.11i, ratified in 2004, is a critical standard because it specifies enhanced security mechanisms for Wi-Fi. The initial security mechanism for 802.11 networks, called Wired Equivalent Privacy (WEP), was shown to have severe security weaknesses-enough to discourage many people from deploying wireless. In response, the Wi-Fi Alliance introduced Wi-Fi Protected Access (WPA), a subset of 802.11i, as an intermediate solution to WEP insecurities. The Wi-Fi Alliance refers to its approved, interoperable implementation of the full 802.11i as WPA2. The next section, "WLAN Security," examines the specifics of 802.11i and WPA2. Perhaps the most eagerly awaited 802.11 standard is IEEE 802.11n, which is expected by 2007. A major enhancement to the 802.11 standard, its objective is to increase transmission speeds to 100Mbps and beyond. In fact, the real data throughput is estimated to reach a theoretical 54Mbps. IEEE 802.11n makes use of multiple-input multiple-output (MIMO) technology, which significantly improves performance and boosts the data rate. At the moment, two competing technologies are both MIMO based: WorldWide Spectrum Efficiency (WWiSE)-WWiSE is backed by Broad- com (www.broadcom.com) and other companies. The WWiSE group (www.wwise.org) wants to stay in the 2.4GHz band and use the same 20MHz channels as 802.11b and 802.11g for compatibility. TGn Sync-This technology is backed by Intel (www.intel.com) and Phil- ips (www.philips.com). IEEE 802.11 Task Group n (TGn; www.tgnsync.org) wants to increase the channel width to 40MHz to increase the data rate and use the 5GHz band like 802.11a. In order to speed the 802.11n development process and promote