The Impact of Imperfect Channel State Information on QRD-Based Precoded MIMO-OFDM System

A new closed-loop preceding method has been proposed for MIMO-OFDM systems with limited feedback by using the QR decomposition to the time-domain channel impulse response matrix. In contrast to the other methods where the receiver has to feed back full precoder index of each subcarrier or reduced index for a group of subcarriers to the transmitter, the GMD-based scheme can substantially reduce the amount of feedback information by returning only one precoder index to the transmitter, regardless of the number of subcarriers and channels. With this approach, the amount of required feedback for the proposed scheme does not grow with the number of subcarriers. This paper considers imperfect channel state information in the transmitter due to a feedback delay in the system.