1. A method for determining a transmit beamformer and quantization noise covariance matrix for uplink multiple-input-multiple-output (MIMO) communications in a cloud radio access network (C-RAN), the method comprising: obtaining, by a central processor (CP), channel state information associated with a mobile device (MD) being served by a plurality of access points (APs) in the C-RAN; generating a channel gain matrix in accordance with the channel state information; establishing a weighted sum-rate maximization model using the channel gain matrix in accordance with power constraints of transmission from the MD to the APs and capacity constraints of fronthaul links between the APs and the CP; and jointly calculating a transmit beamforming vector for the MD and a quantization noise covariance matrix for the APs by applying a weighted minimum-mean-square-error successive convex approximation (WMMSE-SCA) algorithm to solve the weighted sum-rate maximization model.