Algorithm 1 Iterative Precoder Design for Network Massive MIMO OWC System.

Input: The channel matrix $\mathbf{H}$, the noise variance ${\sigma }^2$ and total power constrant P.      Output: The precoding matrix ${\mathbf{P}}_{j,m}$. 1:Initialize the precoding matrix satisfying the power constraint ${\sum }_{i=1}^U\mathrm{tr}\left({\mathbf{P}}_{i,\ell }{\mathbf{P}}_{i,\ell }^T\right)\le P$. 2:for  $\mathit{l}=1$,..., $\mathit{L}$ do 3:    Initialize variables for bisection search: ${\lambda }_{\min }$, ${\lambda }_{\max }$. 4:    while ${\lambda }_{\max }-{\lambda }_{\min }>ϵ$ do 5:        Compute ${\lambda }_{\ell }={\displaystyle \frac{1}{2}}({\lambda }_{\min }+{\lambda }_{\max })$. 6:        Compute the optimal precoding matrix ${\mathbf{P}}_{j,m}$ by using (12). 7:        Calculate total power p. 8:        if $p>P$ then 9:           ${\lambda }_{\min }={\lambda }_{\ell }$ 10:        else 11:           ${\lambda }_{\max }={\lambda }_{\ell }$ 12:        end if 13:    end while 14:    until: convergence or predefined value. 15:end for