A Square-Root Adaptive V-BLAST Algorithm for Fast Time-Varying MIMO Channels

Among the methods that have been proposed for a Multiple-Input Multiple-Output (MIMO) receiver, the V-BLAST algorithm provides a good compromise between transmission rate, achievable diversity, and decoding complexity. In this paper, we derive a new adaptive V-BLAST type equalization scheme for fast time varying, flat fading MIMO channels. The proposed equalizer stems from the Cholesky factorization of MIMO system´s output data autocorrelation matrix and the equalizer´s filters are updated in time using numerically robust unitary Givens rotations. The new square-root algorithm exhibits identical performance to a recently proposed V-BLAST adaptive algorithm, offering at the same time substantially reduced computational complexity. Moreover, as expected due to its square-root form and verified by simulations, the algorithm exhibits particularly favourable numerical behaviour.