Phase Rotations of SVD-Based Precoders in MIMO-OFDM for Improved Channel Estimation

In a multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system, the conventional singular value decomposition (SVD) based precoders may destroy the smoothness of the effective channel, - i.e., the concatenation of the precoders and the channel - in the frequency domain, causing difficulties to the channel estimation. This letter proposes a phase-rotated SVD (PR-SVD) via exploiting the phase non-uniqueness of SVD to make the effective channel as smooth as possible in the frequency domain to facilitate the channel estimation. The simulation results verify that the proposed PR-SVD based precoding method can improve the channel estimation and consequently can significantly outperform the state-of-the-art method in bit error rate (BER).