Performance of hybrid and pure analog CSI feedback in MIMO systems with time-selective fading

In a Frequency division duplex (FDD) system, knowledge of channel state information (CSI) at the transmitter requires a closed feedback loop. In this thesis, we examine system performance associated with different types of feedback operating in time-selective Rayleigh fading channels. For a singleuser system with multiple transmit antennas, we consider hybrid analog/digital feedback, which is an extension for the traditional digital-only codebook feedback. An extra analog symbol that encapsulates channel’s amplitude and phase information that is otherwise lost in the codebook quantization process is fed back for channel tracking purpose. For a multiuser multiple-input-multipleoutput (MIMO) system, we consider the deployment of pure analog CSI feedback. A modified minimum mean square error (MMSE) criterion is used to incorporate downlink channel prediction into the precoder design and user selection process. In both cases, the proposed types of CSI feedback can achieve better BER in comparison to digital CSI feedback.