A Low-Complexity LS Turbo Channel Estimation Technique for MU-MIMO Systems

Turbo channel estimation algorithms can improve estimation accuracy in multiuser (MU) multi-input multi-output (MIMO) systems. However, the conventional least squares (LS) turbo channel estimation technique based on the maximum likelihood approach is difficult to be performed in large MU-MIMO systems since it requires a cubic complexity order O(κ
³
N
_T
³
N
_R
³
) for a system constant κ and numbers of N
_T
-transmit and N
_R
-receive antennas. This is because the conventional technique computes inversion of a covariance matrix whose size is proportional to κN
_T
N
_R
. We propose a new low-complexity LS estimation technique that requires a complexity order O(κ
³
N
_T
³
) only by utilizing algebraic property on the covariance matrix. Simulation results shown in this letter verify that the proposed technique significantly reduces processing time without sacrificing the estimation performance.