Channel estimation in turbo-BLAST detectors using EM algorithm

We consider channel re-estimation based on the EM (expectation maximization) algorithm in an iterative MIMO detector based on parallel interference cancellation, also known under the name of turbo-BLAST. While providing an appropriate formulation of EM, we show that a previously proposed EM implementation gives a biased estimate, and propose modifications in the EM implementation in order to obtain an unbiased estimate. Testing the proposed algorithms by simulations, we show that the achieved improvement is considerable for important diversity orders.