SNAP – POP for Massive MIMO Systems

Massive multiple-input multiple-output (MIMO) has gained a tremendous amount of attention as a key enabler of fifth-generation cellular systems. The majority of the vast literature on massive MIMO is based on fully digital processing, where each antenna element in the massive array is equipped with an up/down-conversion chain. Unlike previous works, we present a suite of greedy algorithms using pure analog processing which approach the performance of uplink digital zero-forcing (ZF) combining. Based on successive nulling and amplification processing (SNAP), the proposed techniques are evaluated in a multi-user context over a range of heterogeneous channel models. Rigorous comparisons are then made to other benchmark analog techniques, digital ZF and an upper bound on analog processing. The most promising approach is shown to have very low-complexity and robustness against a variety of channel conditions, while providing useful performance gains.