Also known as adaptive antennas, these use an array of antennas in combination with smart signal processing algorithms that track the location of a mobile client device using techniques such as the direction of arrival of a signal. The location or angular direction is then used to calculate beam-forming vectors to focus more of the power of the antenna beam on the mobile target. Smart antennas are used in cellular mobile phone systems and in proposed wireless broadband technologies such as 802.16e-2005 (WiMAX) and 802.11n (MIMO). See also SDMA.