Robust Training Sequence Design for Spatially Correlated MIMO Channel Estimation Using Affine Precoder

A robust superimposed training sequence design is proposed for spatially correlated MIMO channel estimation. The proposed scheme does not require accurate knowledge about the spatial correlation matrix and it is shown to outperform robust correlated MIMO channel estimators such as relaxed MMSE (RMMSE) and least-squares-RMMSE (LSRMMSE). Since the training sequence is overlaid into the data stream, spectral efficiency of the system is higher than those that use time-multiplex pilots. A solution for the sequence can be obtained easily by using an iterative algorithm which is guaranteed to converge as long as the training sequence matrix is initialized to have full rank.