Improving low-delay MIMO-OFDM channel estimation

To overcome performance degradation in mobile multiple input multiple output (MIMO) orthogonal frequency-division multiplexing (OFDM) spatial multiplexing downlink systems an improved channel estimation algorithm is proposed. It yields channel estimates after every OFDM symbol reflecting time-variant channel behavior and provides data with approx. 4 bit/s/Hz for a 4×4 MIMO setup due to a decision directed scheme. Through the usage of short LDPC codes and employing a MIMO-OFDM symbol reconstruction method from the LDPC decoder output significant gains in estimation accuracy were realized in computer experiments even in high velocity scenarios. Simulation results based on 3GPP MIMO spatial channel model show the estimation accuracy for a range of velocities which are underlined by comparison of bit error rates with perfect channel state information and the channel estimation.