Improved channel estimation for OFDM based systems with transmitter diversity

Orthogonal frequency division multiplexing (OFDM) transmitter diversity techniques have been shown to be efficient means of achieving near optimal diversity gain in frequency selective fading channels. For these systems, knowledge of the channel parameters is required at the receiver for diversity combining and decoding. We propose a pilot-symbol assisted channel estimator using DFT-based and linear interpolation for OFDM based systems with two antenna transmitter diversity. We then consider four transmit antenna systems and propose new channel estimation techniques, which allow estimation and separation of the channel state information of the different transmit antennas without changing the preamble structure of the system.