An Efficient CQI Feedback Scheme for Multi-user and Single-User MIMO/OFDMA Systems

An opportunistic scheduling is adopted to improve the capacity of the system by exploiting the multi-user diversity (MUDiv) of multi-user MIMO (MU-MIMO) systems. However, it requires a large amount of feedback carrying the channel quality information (CQI) of each user to the transmitter. The considered per user unitary and rate control (PU²RC) needs to feedback the preferred precoding index and its CQIs, and it has a defect in scheduling the streams using user grouping. In order to overcome these drawbacks, a novel feedback reduction scheme is proposed and is improved for OFDMA systems which can support single-user MIMO (SU-MIMO) and multi-user MIMO (MU-MIMO) effectively. It employs transmitter controlled precoding and opportunistic feedback (TCP-OFB) in conjunction with frequency scheduling and single/multi-user allocation.