LTF-based vs. pilot-based MIMO-OFDM Channel Estimation algorithms: An experimental study in 5.2 GHz wireless channel

This paper outlines two classes of channel estimation (CE) techniques, namely the long training field (LTF)-based CE as well as the pilot-based CE. Both LTF and pilot patterns are taken from the 802.11n Draft 2.0 standard. The performance of these two CE classes is evaluated with the aid of actual captured data, provided by experiments under two different propagation scenarios. The first scenario represents the slow time-varying channels, which involve line-of-sight (LOS) outdoor transmission over a distance of 7.5 km. By contrast, the second case corresponds to a Non-LOS indoor environment, where the transmitter and receiver are approximately 15 meters apart, and located in different rooms. Our experimental study shows that the LTF-based CE outperforms the pilot-based CE for slow time-varying outdoor LOS channels, while for indoor NLOS channels, it fails completely. On the other hand, pilot-based CE works in both test cases. Unfortunately, this method is very sensitive to timing synchronization.