Contents I. Introduction
The success story of MIMO technology in terrestrial applications now spans more than a decade with spectacular results, as it offers substantial leverage in realizing the next generation gigabit wireless [1]. The reason for the respective intensive research is that MIMO technology offers many advantages and degrees-of-freedom, such as: (a) space and multiuser diversity gain, (b) spatial multiplexing gain, (c) array and coding gain, and (d) interference reduction. The salient feature of MIMO-based systems is that the above merits come from an information theory point of view at no extra cost concerning transmit power or bandwidth. Instead, MIMO-based systems take advantage of what is probably the last unexploited frontier in wireless communications, the spatial domain. A testimony to its success is that different aspects of MIMO technology are being planned or have already been incorporated in wireless terrestrial standards, such as the IEEE 802.11n, 802.16e, 802.16m, 802.20, 802.22, 3GPP Releases 7, 8 (LTE) and 99, 3GPP2 UMB, DVB-T2 among others.
