Novel smart antennas for applying SDMA to cellular mobile communication systems

The popularization of mobile communication has necessitated efficient use of the radio spectrum. Space-division-multiple-access (SDMA), which enables several users to use the same communication channel simultaneously by forming individual radiation patterns for the users, is an attractive candidate to reuse the frequency spectrum efficiently. However, there still remain problems for applying SDMA to actual cellular systems. These problems are summarized. Then, as solutions to overcome the problems, a new smart antenna configuration comprising sub-arrays and utilizing a space time coding (STC) technique, and a new smart antenna system utilizing space and polarization control are proposed. The effectiveness of the proposed antennas is presented.