A RIS-based Subspace Channel Estimation for MIMO Virtual Carrier OFDM Systems

The repetition inde x scheme (RIS) is ofte n applied to the channel estimation o f orthogonal freque ncy division multiplexing (OFDM) s ystems in th e s cenario th at th e n umbers of re ceive antennas and tr ansmit ante nnas are e qual. In this paper, we apply RIS me thod to th e channel estimation of cyclic prefixing (CP) multiple - input multiple-output (M IMO) OF DM systems with virtual carriers. The signal model is first simplified to remove the rank deficiency due to the virtual carriers. We use the RIS method and circular matrix property to generate times of equivalent symbols so as that th e ch annel es timation ca n converge with fe w received OFDM b lock. Th e RI S me thod suffers from th e nonwhite noise effects. We fu rther calculate the noise co rrelation matri ces. T hen a p re-whitening te chnique is developed fr om the Cholesky fac torization of the n oise correlation mat rix. Comp uter S imulations wil l d emonstrate t he effectiveness of the proposed channel estimation.