Efficient Channel Estimation Schemes for MIMO OFDM Systems With NULL Subcarriers
In this paper, channel estimation schemes as well as low crest-factor preamble construction are presented for practical MIMO OFDM systems with NULL subcarriers. In the presence of NULL subcarriers, the performance of the channel estimator in degrades considerably. Therefore, Maximum-Likelihood (ML) channel estimators were proposed for MIMO OFDM systems with NULL subcarriers. However, they have relatively high computational complexity. Thus, more efficient schemes are proposed in the paper, with regard to two different cases of NULL subcarrier usages: only DC subcarrier is null or both DC and high frequency subcarriers are null. Simulation results show that the new schemes achieve performances near the optimum error bound.