  A fast algorithm for inverse Cholesky factorization is proposed, to compute a
triangular square-root of the estimation error covariance matrix for Vertical
Bell Laboratories Layered Space-Time architecture (V-BLAST). It is then applied
to propose an improved square-root algorithm for V-BLAST, which speedups
several steps in the previous one, and can offer further computational savings
in MIMO Orthogonal Frequency Division Multiplexing (OFDM) systems. Compared to
the conventional inverse Cholesky factorization, the proposed one avoids the
back substitution (of the Cholesky factor), and then requires only half
divisions. The proposed V-BLAST algorithm is faster than the existing efficient
V-BLAST algorithms. The expected speedups of the proposed square-root V-BLAST
algorithm over the previous one and the fastest known recursive V-BLAST
algorithm are 3.9~5.2 and 1.05~1.4, respectively.
