3G MIMO describes MIMO techniques which have been considered as 3G standard techniques. MIMO, as the state of the art of intelligent antenna (IA), improves the performance of radio systems by embedding electronics intelligence into the spatial processing unit. Spatial processing includes spatial precoding at the transmitter and spatial postcoding at the receiver, which are dual each other from information signal processing theoretic point of view. Intelligent antenna is technology which represents smart antenna, multiple antenna (MIMO), self-tracking directional antenna, cooperative virtual antenna and so on. Technology Spatial precoding of intelligent antenna includes spatial beamforming and spatial coding. In wireless communications, spatial precoding has been developing for high reliability, high rate and lower interference as shown in the following table. Summary of 3G MIMO The table summarizes the history of 3G MIMO techniques candidated for 3G standards. Although the table additionally contains the future part but the contents are not clearly filled out since the future is not precisely predictable. IA in ad hoc networking IA technology enables client terminals, which have either multiple antennas or a self-tracking directional antenna, to communicate to each other with as high as possible signal-to-interference-and-noise ratio (SINR). Assume that there is a source terminal, a destination terminal, and some candidate interference terminals. Compared to conventional approaches, an advanced IA based terminal will perform spatial precoding (spatial beamforming and/or spatial coding) not only to enhance the signal power at the destination terminal but also to diminish the interfering power at interference terminals. As a human does, the advanced IA terminal is given to know that occurring high interference to other terminals will eventually degrade the performance of the associated wireless network. Principal Issues of Research The following items list the issues of the multiple antenna research aims to improve the performance of radio communications. Intelligent antenna Smart antenna Digital antenna array Multiple-input multiple-output (MIMO) Beamforming Diversity combining Diversity scheme Space–time code Spatial multiplexing Space-division multiple access (SDMA) Advanced MIMO communications Multi-user MIMO Precoding Dirty paper coding (DPC) Cooperative wireless communications Cooperative diversity Principal Definitions Definitions Here are the definition of principal keywords to clarify the objective and the operations of intelligent antenna. Reference Web Sites The following items list the web sites related to the multiple antenna research. MARS, Bell Laboratories — Multiple Antenna Research and Solutions (MARS) is a research group on multiple antenna and space time coding Lucent — The goal of intelligent