massive mimo Fundamentals, Opportunities and Challenges

应用背景Massive multiuser MIMO (MISO): ◮ M ≫ K ≫ 1 (think 100 × 10 or 500 × 50) ◮ coherent, but simple, processing ◮ Potential to dramatically improve rate & reliability ◮ Potential to drastically scale down TX power ◮ Not only theory, at least one known testbed (64× ∼10) 关键技术 Massive MIMO Operation Not enough resources for pilots & CSI feedback, so operate in TDD. ◮ On the uplink, ◮ acquire CSI from uplink pilots and/or blindly from data ◮ detect symbols ◮ M ≫ K ⇒ linear processing (MRC, ZF, MMSE) nearly optimal ◮ On the downlink, ◮ use CSI obtained on the uplink ◮ make necessary adjustments based on reciprocity calibration ◮ apply multiuser MIMO precoding ◮ simple precoders desirable (and very good!): MRT, ZF, MMSE, ... ◮ MRC/MRT operation ◮ intracell interference will appear as