Pilot-aided channel estimation schemes for OFDM systems with cyclic delay diversity

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