Figure 5

Required SNR threshold γ ₀ for DBF to guarantee a given outage probability. It is presented a function of the number active array elements. Outage probability: Pr_out = 0.02 (∘), ${\text{Pr}}_{\text{out}}=0.1(\square$), and Pr_out = 0.5 (◇). Channel feedback: no CSI (red), N = 1 (green), N = 2 (blue), and N = 3 (magenta). Solid (black) line: full CSI at array elements. Simulated values are denoted by (^∗). Channel amplitudes are fixed with perfect power balance.