An overview of Multiple-Input Multiple-Output (MIMO) systems

In this article, a novel multiple-input multiple-output (MIMO) technology is presented. MIMO is a technique that gives the opportunity to achieve very high data rates in radio networks, thanks to utilizing numerous spatial channels, resulting from the use of many antennas on one or both sides of the radio link. In the first part of this article, we describe the basic facts referring to MIMO, including the major benefits from using this technology (out of which diversity and multiplexing gains are arguably the most significant). After that, the mathematical background of MIMO is briefly outlined. The subsequent part refers to one of the most significant issues connected with multiple-antenna systems, that is the channel capacity. Employing MIMO allows to increase this capacity and consequently to boost transmission rate. Basic definitions and formulas for capacity in different cases are provided. The next part explains two most common methods of transmission, i.e.: spatial multiplexing and space-time coding. Finally, in the last part we summarize and conclude the article.