Scaling Laws of Scheduling Gain for Uplink Massive MIMO Systems: Is User Scheduling Still Beneficial for Massive MIMO?

Abstract

In this paper, the scaling laws of scheduling gain and the feasibility of user scheduling for uplink massive multiple input–multiple output (MIMO) systems are investigated by analyzing the second moment of mutual information. We consider two well-known linear receivers of matched filter (MF) and zero-forcing (ZF). The exact distribution of the signal-to-interference-plus-noise ratio (SINR) and its moment-generating function are first obtained, and the approximated variance of the mutual information for a user is derived as a closed form with a function of the number of antennas. The achievable scheduling gain under the optimal user scheduler is then derived using the Gaussianity of the sum rate. From the analyses and simulation results, it is found that the scheduling gain for the MF receiver increases with the number of base station (BS) antennas, while that for the ZF receiver decreases as the number of BS antennas increases, for most cases (except some impractical scenarios). Therefore, it is verified that user scheduling is still beneficial for the MF receiver while random user selection is sufficient for the ZF receiver in massive MIMO systems.

Self-Interference Channel Training for Full-Duplex Massive MIMO Systems

“…It is expected that 6G will provide an ultimate experience beyond even that of 5G NR by enabling new services and applications such as multisensory extended reality, mobile holograms, connected robotics, autonomous systems, and wireless brain-computer interactions [ 5 , 6 , 7 ]. To meet the explosive data traffic expected in the 6G era, massive multiple-input multiple-output (MIMO) [ 8 , 9 , 10 , 11 , 12 , 13 ] and full-duplex (FD) [ 14 , 15 , 16 ] are indispensable technologies for improving the network capacity.…”

“…In massive MIMO systems, the base station (BS) is equipped with a large number of antennas, and the spectral efficiency can be significantly increased by simultaneously serving frequency resources and a large amount of user equipment (UE) concurrently [ 8 , 9 , 10 , 11 , 12 , 13 ]. Meanwhile, in FD systems, downlink (DL) and uplink (UL) transmissions occur simultaneously at the transceiver at the same time and frequency resource [ 14 , 15 ].…”