Algorithm 2 Optimal beamforming policy

1:Initiate ${\mathbf{w}}_0$ with constraint (16). Set step size $\lambda ={\lambda }_{int}$, and the minimum step size ${\lambda }_{min}$. Obtain $\left\{{\xi }_i\right\},i\in \mathcal{R}$. 2:Set $n=0$, calculate $R_n=f\left({\mathbf{w}}_n\right)$ by (12). 3: while $\lambda >{\lambda }_{min}$ do 4: Update ${\mathbf{w}}_n^{\prime }$ according to (23) and calculate $R_n^{\prime }=f\left({\mathbf{w}}_n^{\prime }\right)$. 5: If $R_n^{\prime }>R_n$, update $R_{n+1}=R_n^{\prime }$, ${\mathbf{w}}_{n+1}={\mathbf{w}}_n^{\prime }$ and $n\leftarrow n+1$. Otherwise, update $\lambda =\frac{1}{2}\lambda$. 6: end while 7:Output ${\mathbf{w}}_n$, $R_n$.