Current wireless technical challenges include limited bandwidth, interference and signal fading leading to less than ideal performance and reliability. Multiple-input, multiple-output (MIMO) is a compelling new technique that addresses these issues. MIMO essentially multiplies data throughput, with a simultaneous increase in range and reliability, without consuming extra radio frequency spectrum.

The purpose of this paper is to introduce MIMO and multiple antenna technology, provide an overview of smart antenna techniques, and address how MIMO is not just another smart antenna technology but a revolutionary approach that exploits multipath reversing 100 years of thinking.

In the fall of 2004 the first MIMO implementations were introduced for the 802.11 market. MIMO is the key ingredient in every 802.11n standard proposal that will define the next generation of Wi-Fi. MIMO is a technique that can be applied not only to wireless LAN applications but also other wireless technologies and markets such as wide-area and cellular.