Recent works on massive multiple-input multiple-output (MIMO) have shown thata potential breakthrough in capacity gains can be achieved by deploying a verylarge number of antennas at the basestation. In order to achieve theperformance that massive MIMO systems promise, accurate transmit-side channelstate information (CSI) should be available at the basestation. Whiletransmit-side CSI can be obtained by employing channel reciprocity in timedivision duplexing (TDD) systems, explicit feedback of CSI from the userterminal to the basestation is needed for frequency division duplexing (FDD)systems. In this paper, we propose an antenna grouping based feedback reductiontechnique for FDD-based massive MIMO systems. The proposed algorithm, dubbedantenna group beamforming (AGB), maps multiple correlated antenna elements to asingle representative value using pre-designed patterns. The proposed methodmodifies the feedback packet by introducing the concept of a header to select asuitable group pattern and a payload to quantize the reduced dimension channelvector. Simulation results show that the proposed method achieves significantfeedback overhead reduction over conventional approach performing the vectorquantization of whole channel vector under the same target sum raterequirement.
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