What is the Beamforming impact on Capacity?

Beamforming antennas can be used as coverage or capacity strategy.

The array gain from the beamforming process provides higher downlink gain in the service beam and enables higher-order receive diversity in
the uplink. This helps improve cell-edge throughput or extend cell-edge coverage for the minimum desired user throughput.

One way to evaluate the applicability of MIMO and beamforming is through Shannon’s Capacity Theorem. Capacity is a logarithmic curve,
which is linear at low signal-to-interference-plus-noise ratio (SINR) and flattens out at high SINR.

Capacity Vs. SINR

In high-SINR conditions, the capacity increase per unit increase in SINR
is relatively low. In such environments, beamforming—which further improves the signal-to-noise ratio—will be less effective than MIMO, which uses multiple layers in either single- or multiple-user modes, and is
more effective.

At low-SINR conditions, the relation between SINR and capacity is linear.

Beamforming techniques, due to their higher signal gain, prove very
effective in such scenarios. Beamforming that uses the direction of arrival
(DoA) information is more effective in low-scattering and low-SINR environments.

Source: Commscope