Parallel-interference-cancellation-assisted decision-directed channel estimation for OFDM systems using multiple transmit antennas

The number of transmit antennas that can be employed in the context of least-squares (LS) channel estimation contrived for orthogonal frequency division multiplexing (OFDM) systems employing multiple transmit antennas is limited by the ratio of the number of subcarriers and the number of significant channel impulse response (CIR)-related taps. In order to allow for more complex scenarios in terms of the number of transmit antennas and users supported, CIR-related tap prediction-filtering-based parallel interference cancellation (PIC)-assisted decision-directed channel estimation (DDCE) is investigated. New explicit expressions are derived for the estimator´s mean-square error (MSE), and a new iterative procedure is devised for the offline optimization of the CIR-related tap predictor coefficients. These new expressions are capable of accounting for the estimator´s novel recursive structure. In the context of our performance results, it is demonstrated, for example, that the estimator is capable of supporting L=16 transmit antennas, when assuming K=512 subcarriers and K₀=64 significant CIR taps, while LS-optimized DDCE would be limited to employing L=8 transmit antennas.