ion. MIMO techniques based on spatial multiplexing (such as D-BLAST and V-BLAST) increase the system capacity significantly by serial-to- parallel transmission. For correlated MIMO environments, channel information should be fed back and precoding is performed at the transmitter. As another kind of MIMO structure application, beam-forming should also be considered and analyzed according to practical requirements. Furthermore, advanced MIMO techniques should be paid more attention because the number of receiving antennas may be fewer than those of transmitting antennas in the forward link. Based on some special network architectures, such as generalized distributed antenna architecture, the MIMO technique could embody its superiority in more application forms (e.g., spaced MIMO, distributed MIMO, and virtual MIMO). Additionally, adaptive MIMO schemes should be considered in the FuTURE TDD system. 2.2.2.2.7 Link Adaptation The FuTURE TDD system should allow for link adaptation, which involves not only AMC but also adaptive MIMO and other advanced adaptive transmission techniques. In addition, the signaling overhead in both forward and reverse link should be considered. Adaptive modulation and coding (AMC). Adaptive modulation and coding as one of the effective link adaptation schemes should be considered and adopted in the FuTURE TDD system to improve the system capacity with high spectral efficiency. Systems in TDD mode have channel reciprocity because both forward and reverse links are accommodated in the same frequency band. Consequently, the system can estimate the CSI from reception. Hence, TDD systems are more suitable to adopt the AMC technique. By employing the AMC technique, the power of the transmitted signal is held constant over a frame interval, and the modulation and coding schemes (MCSs) can be chosen adaptively according to channel conditions. The bearer service (BS) may compute the best combination of MCSs either based on postdetection SNR measurement reported by AT or based on signal-to-noise (SNR