Frequency Reuse of Beam Allocation for Multiuser Massive MIMO Systems

Abstract—Massive multiple-input-multiple-output (MIMO)

has become a promising technique to provide high-data-rate

communication in fifth-generation (5G) mobile systems, thanks to

its ability to form narrow and high-gain beams. Among various

massive MIMO beamforming techniques, the fixed-beam scheme

has attracted considerable attention due to its simplicity. In this

paper, we focus on a fixed-beam based multiuser massive MIMO

system where each user is served by a beam allocated to it. To

maximize the sum data rate, a greedy beam allocation algorithm

is proposed under the practical condition that the number of

radio frequency (RF) chains is smaller than the number of users.

Simulation results show that our proposed greedy algorithm

achieves nearly optimal sum data rate. As only the sum data rate

is optimized, there are some “worst-case” users who could suffer

from strong inter-beam interference and thus experience low

data rate. To improve the individual data rates of the worst-case

users while maintaining the sum data rate, an adaptive frequency

reuse scheme is proposed. Simulation results corroborate that our

proposed adaptive frequency reuse strategy can greatly improve

the worst-case users’ data rates and the max-min fairness among

served users without sacrificing the sum data rate.