BACK Wireless N
802.11n or Wireless-N is the third-generation WiFi standard for wireless home networking. Wireless-N supports data transfer speeds which are comparable with Fast Ethernet (wired networking) and also offers a greater wireless range over 802.11g and earlier 802.11b equipment. To achieve these increases speeds and range, MIMO ("Multiple In and Multiple Out") technology has been employed in Wireless N. MIMO wireless communication has 3 different features: 1)Normally when a signal is transmitted from A to B the signal will reflect off objects (in an indoor environment that means furniture and construction material) and reach the receiving antenna via multiple paths, which causes interference and fading, affecting the quality of the signal received. However MIMO uses multiple path transmission to create a stronger signal with greater range. The data is split into multiple spatial streams and then these data streams are transmitted through separate antennas to multiple corresponding receivers. This techinique is called spatial multiplexing. It was found that if the number of spatial streams was doubled then the raw data transfer rate can be doubled too, which makes much better use of the available bandwidth. 2)The multiple receiver antennas also means that the clearest data path can be received and analysed, even when there is interference, whch means that the range can be increased for receiving data. If interference occurs, another antenna will be switched to. Using multiple transmittor and multiple receiver antennas is called Antenna Diversity. 3) Beamforming technologies are also used in MIMO - for improving received signal gain and reducing interference to other users. Beamforming focuses the radio signal directly along the path for the receiving antenna to improve the range and overall performance. Wireless-N Access Points are also backwards compatible which means that they can be used with earlier wireless devices such as 802.11 a, b or g in the same network. This however means that the Wireless-N router cannot perform at its maximum and the operation of the whole network is slowed. Wireless-N routers should therefore be able to operate in three modes: - Legacy: only 802.11 a, b and g - Mixed: both 802.11 a, b, g and n - Greenfield: only 802.11n which means maximum performance. The table below shows the comparison between the Wireless Standards:  BACK
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