Adaptive Space-Time Coding and its Implementation in MIMO Antenna Systems

The introduction of Multiple-Input Multiple-Output (MIMO) opened the door for space-time processing (STP) techniques to improve the transmission reliably and spectral efficiency. STP algorithms have been mainly proposed to achieve either enhancement in the link quality (through spatial diversity) or throughput gain (through spatial multiplexing). The simultaneous enhancement of link reliability and throughput gain are competing performance objectives. In addition, the performance of either of these methods is highly dependent on the MIMO channel conditions. If the MIMO channel is spatially uncorrelated, it is known to be well conditioned to achieve spatial multiplexing gain. On the other hand, if the MIMO channel is spatially correlated, it is much less able to support spatial multiplexing; hence, performance can be improved through spatial diversity. This paper presents an adaptive layered space-time (LST) processing method. The proposed scheme is shown to be able to adapt to a broad range of MIMO channel environments, providing a significant performance improvement over the conventional non-adaptive STP methods. Furthermore, we discuss some implementation issues of the proposed scheme.