Pilot Frequency Nulling based Channel Estimation for Multiple QR-Decompositions with Transposed Channel Matrix SDM/OFDM

In MIMO systems, MLD/SDM provides the best BER performance. However, the complexity of MLD increases exponentially according to the modulation level and number of transmit antenna branches. Moreover, the preamble structure is also serious problem. With increasing the number of transmit antenna branches, more pilot symbol is required to estimate the accurate channel state infomation (CSI). In this case, the effective transmission rate is degraded and different packet structure is also required. To reduce these problems, in this paper, we propose the pilot frequency nulling based channel estimation scheme for multiple QR-decompositions with transposed channel matrix SDM/OFDM.