Utilizing temporal correlation in multiuser MIMO feedback

In modern downlink wireless communication systems, multiple antennas are being increasingly used at the transmitter to support multiple users. To increase the sum-rate, it has been shown that downlink channel state information (CSI) must be utilized at the transmitter. Especially in frequency division duplexing (FDD) systems, feedback of this CSI is necessary from each of the users to provide the transmitter with this knowledge. The amount of feedback should be as small as possible to reduce the uplink burden. Most work on the design of this feedback has assumed a channel that fades independently from block to block. However, in practice, the channel is correlated in time. In this paper, we propose a limited feedback approach utilizing the temporal channel correlation information in multiuser downlink MIMO systems. We analyze the impact of the feedback amount on sum-rate performance when a zero-forcing beamformer is used at a base station. Simulations show that the proposed feedback method utilizing the temporal channel correlation information outperforms previous schemes not utilizing the temporal channel correlation information.