From: Robust SINR-constrained MISO downlink beamforming: when is semidefinite programming relaxation tight?
Dual variable
Constraint
μ k
λ k ≥ 0
U k
X k + λ k I X k h ~ k h ~ k H X k H h ~ k H X k h ~ k − σ k 2 − λ k ε k 2 ≽0
Z k
G k ≽0