Massive multi-user MIMO is a promising technique to increase capacity with spatial filtering for spectrum reuse, and increasing SNR through array gain. There are many advantages to increasing antenna and user count in these arrays, but there is also much debate on how best to do so efficiently. An especially important decision is where to place the beamformer in the signal chain. This work proposes a hardware informed model for comparison between analog and digital beamforming, breaking down the decision into intuitive designer chosen specifications and comparing in power. The model finds that analog baseband beamforming is critical for scaling to wide-bandwidth and large arrays, especially in the presence of interferers. The hardware assumptions in the model are tested in a 16x16 beamforming receiver array in 28nm silicon. Design techniques such as noise or bandwidth limited design, two stage beamforming, and offset correction are used in the circuit implementation. The ASIC was packaged and used in a real time demonstration which performs multi-user and multi-panel operation.




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