14.1 A 71-to-86GHz Packaged 16-Element by 16-Beam Multi-User Beamforming Integrated Receiver in 28nm CMOS

Multi-User MIMO (MU-MIMO) at mm-wave is a promising technique for high-capacity wireless access. A base-station array of M antennas simultaneously steers K independent beams, which enables spatial multiplexing and channel bandwidth reuse across multiple users. It has been shown that for M≫K (i.e. massive MIMO), linear algorithms can achieve near-optimal user tracking and spatial interference rejection [1]. The power and area demands of massive arrays are minimized with a fully connected architecture, where each beam is a combination of all available array elements [2]. However, a massive fully connected array results in significant hardware complexity.