Adaptive channel direction quantization for frequency selective channels

In this work, we consider the calculation of channel state information (CSI) feedback for frequency selective OFDM based multiple input single output (MISO) wireless communication systems. We focus on the quantization and feedback of the normalized MISO channel vector which is required, e.g., for multi-user beamforming systems. Such systems require accurate CSI at the transmitter to avoid interference between users. Our algorithms provide feedback information for a subset of the OFDM subcarriers to reduce the feedback overhead. Residual correlation between such CSI pilot positions in time and frequency is exploited to improve the quantization accuracy. This work is an extension of our previous proposal [1] to frequency selective OFDM systems.