terference caused by the timing offset impacts the channel estimation accu- racy in both CSI measurement and data demodulation, resulting in significant MIMO per- formance degradation. It can be shown that the performance loss due to timing offset is not negligible, especially in the case of negative timing offset. For positive timing offset, when the aggregated signals are received with the timing difference shorter than the cyclic prefix length, less ISI is incurred. For the negative timing offset, since the incurred ISI cannot be mitigated by removing the cyclic prefix, severe performance loss is caused. The capability of interference suppression in the receiver is critical for the performance of non-coherent MIMO transmission. For coherent MIMO transmission, a traditional linear receiver such as MRC/MMSE can be used to achieve acceptable performance, while for non-coherent MIMO transmission, an advanced receiver is required. If the data streams from different directions (especially in the case of widely spaced panels) arrive at the UE in different angles, a simple linear MMSE receiver may be sufficient. However, the per- formance gain depends on the remaining interference after the space-domain interference rejection by the MMSE processing. If different streams arrive at the UE from the same or adjacent directions (e.g., different antenna panels located in a centralized manner), Chapter 4 Downlink MIMO operation in sub-6 GHz Single CSI-RS Multiple CSI-RS SRS-based CSI-RS may be beamformed Combines beam selection with codebook Allows codebook feedback feedback (multiple beamformed CSI-RS with CRI Exploits TDD reciprocity feature Similar to LTE class-A CSI feedback (gNB feedback) Similar to SRS-based operation in LTE transmit CSI-RS; UE computes RI/PMI/CQI) Similar to LTE Class-B CSI Feedback (gNB Supports arrays with arbitrary number of TXRUs Maximum of 32 ports in the CSI-RS (codebooks transmits one or more CSI-RS, each in different are defined for up to 32 ports) directions; UE computes CRI/PMI/CQI) Procedur