Short-term and long-term diagonalization of correlated MIMO channels with adaptive modulation

Theoretical results on MIMO capacity maximization suggest the decoupling of the MIMO channel into independent subchannels with optimum water-filling on these subchannels. Those results inspire the development of real systems that diagonalize the MIMO channel and adaptively control the modulation on each of the resulting subchannels. We study the design of a fully adaptive transmitter, where transmit filtering and adaptive modulation is controlled by short-term as well as long-term channel state information (channel correlation), where the focus is on channels with correlated fading at transmitter and receiver array. To this end, we are motivating the use of long-term channel eigenmodes by capacity-independent considerations. Simulation results confirm the potential of fully adaptive transmit processing.