Large antenna arrays will be needed in future millimeter wave (mmWave)cellular networks, enabling a large number of different possible antennaarchitectures and multiple-input multiple-output (MIMO) techniques. It is stillunclear which MIMO technique is most desirable as a function of differentnetwork parameters. This paper, therefore, compares the coverage and rateperformance of hybrid beamforming enabled multi-user (MU) MIMO and single-userspatial multiplexing (SM) with single-user analog beamforming (SU-BF). Astochastic geometry model for coverage and rate analysis is proposed forMU-MIMO mmWave cellular networks, taking into account important mmWave-specifichardware constraints for hybrid analog/digital precoders and combiners, and ablockage-dependent channel model which is sparse in angular domain. Theanalytical results highlight the coverage, rate and power consumption tradeoffsin multiuser mmWave networks. With perfect channel state information at thetransmitter and round robin scheduling, MU-MIMO is usually a better choice thanSM or SU-BF in mmWave cellular networks. This observation, however, neglectsany overhead due to channel acquisition or computational complexity.Incorporating the impact of such overheads, our results can be re-interpretedso as to quantify the minimum allowable efficiency of MU-MIMO to provide higherrates than SM or SU-BF.
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