Techniques and examples of overhead reduction for linear combination codebook and feedback mechanism in mobile communications are described. A user equipment (UE) receives from a base station of a network one or more reference signals via a communication link between the UE and the base station. The UE constructs a channel state information (CSI) feedback by utilizing a correlation of channel responses in a frequency domain to reduce feedback overhead. The UE then transmits the CSI feedback to the base station.