Limited Feedback for MISO-OFDM Systems

A multiple input single output orthogonal frequency division multiplexing (MISO-OFDM) system with feedback-based transmit beamforming is investigated. Since existing algorithms do not take frequency and temporal correlation of the channel transfer function into account simultaneously, we propose to use a resource block (RB)-based feedback structure which utilizes both types of correlation on a RB basis. This method spends a few more bits on the first OFDM symbol in a RB and dramatically reduces the overall feedback overhead by exploiting temporal and frequency correlation. The RB-based algorithm is also shown to be able to restrain the SNR loss due to quantization of the optimal beamformer.