Pre- and Post-Coding in Millimeter-Wave Massive MIMO

摘要

Multiple Input Multiple Output (MIMO) signal processing with full Channel State Information (full-CSI) uses pre-and post-coding at the transmitter and receiver sides, respectively, which is based on singular-value decomposition (SVD) of the channel matrix in case of narrow-band millimeter-wave channels. It is shown in this contribution that such a type of coding can be partly implemented using hardware Butler Matrices, whose design is well established in the literature. This is especially important in millimeter-wave massive MIMO, where fully digital beam-forming is not feasible, and a hybrid analog/digital signal processing becomes necessary. The presented analysis shows clearly how clustered multiple-reflection propagation paths, which typically characterize millimeter-wave channels, are geometrically assigned to the narrow beams simultaneously created by the Butler Matrix. A comparison between fully digital and hybrid MIMO signal processing in terms of the used hardware is also presented. Demonstrating simulations justify the achieved results.