Multiplexing Gain Analysis of mmWave Massive MIMO Systems With Distributed Antenna Subarrays.

This paper investigates a point-to-point millimeter-wave (mmWave) massive MIMO system in which the transmitter and receiver consist of $K_t$ and $K_r$ distributed antenna subarrays, respectively. All the subchannel matrices between each pair of subarrays at the transmitter and the receiver are assumed to be mutually independent and known at the transmitter and the receiver. To quantify the potential of spatial multiplexing in such a system, the multiplexing gain is defined and analyzed when the numbers of antennas at subarrays go to infinity while the transmit power is held fixed. In particular, assuming that all subchannels have the same average number of propagation paths $\bar{L}$ , the paper shows that an average maximum multiplexing gain of $K_rK_t\bar{L}$ can be achieved. This result means that the multiplexing gain under a distributed array architecture can statistically increase in proportion with $K_rK_t$. The multiplexing gain analysis is also extended to the multiuser scenario. Simulation results obtained with the hybrid analog/digital processing finally corroborate the analytical results. [ABSTRACT FROM AUTHOR]