  Non-cooperative cellular massive MIMO, combined with power control, is known
to lead to significant improvements in per-user throughput compared with
conventional LTE technology. In this paper, we investigate further refinements
to massive MIMO, first, in the form of three-fold sectorization, and second,
coordinated multi-point operation (with and without sectorization), in which
the three base stations cooperate in the joint service of their users. For
these scenarios, we analyze the downlink performance for both maximum-ratio and
zero-forcing precoding and derive closed-form lower-bound expressions on the
achievable rate of the users. These expressions are then used to formulate
power optimization problems with two throughput fairness criteria: i)
network-wide max-min fairness, and ii) per-cell max-min fairness. Furthermore,
we provide centralized and decentralized power control strategies to optimize
the transmit powers in the network. We demonstrate that employing sectorized
antenna elements mitigates the detrimental effects of pilot contamination by
rejecting a portion of interfering pilots in the spatial domain during channel
estimation phase. Simulation results with practical sectorized antennas reveal
that sectorization and multi-point coordination combined with sectorization
lead to more than 1.7x and 2.6x improvements in the 95%-likely per-user
throughput, respectively.
