Linear Minimum Mean-Squared Error Channel Estimation for Per-Subcarrier Antenna Selection
The linear minimum Mean-Squared Error (MSE) channel estimator for systems employing per-subcarrier transmit antenna selection is developed. It is shown that the frequency domain correlations after the selection process is approximated well using a simple explicit function. Performance of resultant estimators, which assume a certain correlation model, deteriorates quickly at high Signal-to-Noise Ratios (SNR) when model errors exist. To overcome this deficiency, robust estimators based on the principles of minimising the worst case and expected MSEs over the possible model set are developed. Solution to the latter is given in closed form, and is seen to achieve MSE optimal performance at low SNR while the high SNR performance is the same as that of the Least-Squares (LS) estimator.