Improvements I-IV were proposed to reduce the computational complexity of the
original recursive algorithm for vertical Bell Laboratories layered space-time
architecture (VBLAST). The existing recursive algorithm with speed advantage
and that with memory saving incorporate Improvements I-IV and only Improvements
III-IV into the original algorithm, respectively. To the best of our knowledge,
the algorithm with speed advantage and that with memory saving require the
lowest complexity and the least memories, respectively, among the existing
recursive V-BLAST algorithms.
We propose Improvements V and VI to replace Improvements I and II,
respectively. Instead of the lemma for inversion of partitioned matrix applied
in Improvement I, Improvement V uses another lemma to speed up the matrix
inversion step by the factor of 1.67. Then the formulas adopted in our
Improvement V are applied to deduce Improvement VI, which includes the improved
interference cancellation scheme with memory saving. In the existing algorithm
with speed advantage, the proposed algorithm I with speed advantage replaces
Improvement I with Improvement V, while the proposed algorithm II with both
speed advantage and memory saving replaces Improvements I and II with
Improvements V and VI, respectively. Both proposed algorithms speed up the
existing algorithm with speed advantage by the factor of 1.3, while the
proposed algorithm II achieves the speedup of 1.86 and saves about half
memories, compared to the existing algorithm with memory saving