SAGE based channel estimation and delay tracking scheme in OFDM systems

Pilot subcarriers based channel estimation is necessary in high rate and high speed OFDM systems. In this paper, we present a new channel estimation and delay tracking method in a SAGE (space alternating generalized expectation maximization) framework. The proposed method uses much fewer pilots with special positions that are related to the path number and path delays. The method considered not only the sample-spaced path delays but also the non-sample spaced path delays. The non-sample spaced delay is a more practical situation in wireless communications and this situation will generate an error floor for the traditional channel estimation methods. When the path delay profile changes, a feedback channel is required to inform the transmitter to change the pilot pattern. Analytical results and simulations comparing to the low pass LS channel estimation are given at last.