The 802.11n standard is a Wi-Fi standard that is backward-compatible with 802.11a, b, and g networks. It enables Wi-Fi networks to cover longer distances by overcoming a certain amount of interference. It also increases achievable speeds, increases throughput (user data minus packet headers), and supports more users per access point than earlier Wi-Fi networks. Improvements in the number of users supported in a given amount of airspace are critical as the number of users and applications on Wi-Fi networks increase. 802.11n and 802.11ac mentioned below operate on 5Ghz frequencies. Using MIMO Antennas to Carry More Traffic www.TechnicalPDF.com Improvement in antennas is the reason 802.11n and 802. 11ac use spectrum more efficiently and overcome many "dead spots." A dead spot is an area that access points don't cover because of interference from building materials or the distance from an antenna. The 802.11n access points use MIMO antennas, which were not available in earlier Wi-Fi networks to simultaneously transmit multiple streams at different frequencies within a single channel. 802. 11n is being replaced by the higher- capacity 802.11ac described below. Access points that support both 802.11ac and 802.1 11n are widely available. These are compatible with user devices with only 802.11n computer chips. MIMO antennas are classified by the number of transmit and receive antennas installed within access points and user devices. 2x2 antennas have two transmit and two receiver antennas. 2x3 antennas have two transmit and three receiver antennas. 3x3 antennas have three transmit and three receiver antennas. 4x4 antennas have four transmit and four receiver antennas. 8x8 antennas have eight transmit and eight receiver antennas. Wi-Fi routers with more antennas support more capacity and higher data rates. To achieve the highest speeds and capacity, user devices as well as access points must have an equal number of antennas. See Figure 7-13 for an example of a Wi-Fi access point. www.TechnicalPDF.com LINCBYS BARKON Figure