Effects of improved channel estimation are studied for a proposed IEEE 802.11n OFDM MIMO system. Three channel estimation methods are considered: maximum likelihood (ML), time-domain truncation (TDT) and model-based (MB). TDT and MB are particularly useful when the channel delay spread is short. For an MMSE receiver, MB shows a 1-2.5dB improvement over ML on the packet error rate performance for TGn channels B and D for various modulation and coding schemes. TDT is a simplified version of MB and shows a 1-2dB improvement over ML at low SNRs. But improvements diminish when transmit beamforming is also employed.