Pilot-aided channel estimation for CDD-OFDM systems

Cyclic delay diversity (CDD) is a low-complexity transmit diversity technique for coded orthogonal frequency division multiplexing (OFDM), which transforms a multiple-input channel into an equivalent single-input channel with increased frequency selectivity and provides additional frequency diversity. However, it makes channel estimation more difficult due to the increased frequency selectivity. In this paper, focusing on the direct estimation of the equivalent single-input channel for CDD-OFDM systems, a cyclic cross-correlation channel estimation method based on the equispaced constant-modulus pilot structure is first proposed. Using the statistical parameters of the channel and noise derived by the cyclic cross-correlation channel estimation, an improved channel estimation method based on the Wiener filter is proposed to reduce the estimation error further. Lastly, computation simulations are given to demonstrate the effectiveness of two proposed channel estimation methods for CDD-OFDM systems.