The Common Difference Between MIMO With Other Antennas
  In past 802.11 systems there is a single Radio Frequency (RF) chain on the Wi-Fi device. Multiple antennas use the same hardware to process the radio signal. So only one antenna can transmit or receive at a time as all radio signals need to go through the single RF chain. In MIMO there can be a separate RF chain for each antenna allowing multiple RF chains to coexist. MIMO technology has attracted attention in wireless communications, because it offers significant increases in data throughput and link range without additional bandwidth or increased transmit power. It achieves this goal by spreading the same total transmit power over the antennas to achieve an array gain that improves the spectral efficiency (more bits per second per hertz of bandwidth) or to achieve a diversity gain that improves the link reliability. Multiple Input/Multiple Output (MIMO) is an area of intense development in the wireless industry because it delivers profound gains in range, throughput and reliability. As a result, manufacturers of wireless local area network (WLAN), wireless metropolitan area network (WMAN), and mobile phone equipment are embracing MIMO technology. In this paper we are interested to compare the MIMO Antenna functions with traditional Antenna functions. And we take an example of IRT for illustration. 
M. D. Sirajul Huque, C. Surekha, S. Pavan Kumar Reddy, Vidhisha Yadav
cs.NI