Insights into feedback and feedback signaling for beamformer design

Multi-site cooperative transmission is gaining industrial support in latest standard development. One key criteria to successfully implement a multi-site cooperative transmission system is the need to quantize an expanded set of channels. To maintain quantization precision, codebook size needs to scale roughly exponentially with the number of total antennas and renders quantizing the expanded channel set a computationally demanding task. In this paper, we identify a connection between noncoherent communication and the phase invariant property of beamforming vectors. We leverage techniques from the noncoherent communication literature to design an efficient beamforming vector quantization scheme. Our proposed scheme has a quantization complexity that grows linearly with number of antennas. Simulation results indicate this method has slightly more quantization distortion than RVQ while being significantly more efficient.