  In this paper, we investigate the dynamic power allocation for a visible
light communication (VLC) cellular system consisting of two coordinating
attocells, each equipped with one access-point (AP). The coordinated multipoint
(CoMP) between the two cells is introduced to assist users experiencing high
inter-cell-interference (ICI). Specifically, the coordinated zero-forcing (ZF)
precoding is used to cancel the ICI at the users located near the centers of
the cells, whereas the joint transmission (JT) is employed to eliminate the ICI
at the users located at the edge of both cells and to improve their receptions
as well. Furthermore, two multiple access techniques are invoked within each
cell, namely, non-orthogonal-multiple-access (NOMA) and cooperative
non-orthogonal-multiple-access (C-NOMA). Hence, two multiple access techniques
are proposed for the considered multi-user multi-cell system, namely, the
CoMP-assisted NOMA scheme and the CoMP-assisted C-NOMA scheme. For each scheme,
two power allocation frameworks are formulated each as an optimization problem,
where the objective of the former is maximizing the network sum data rate while
guaranteeing a certain quality-of-service (QoS) for each user, whereas the goal
of the latter is to maximize the minimum data rate among all coexisting users.
The formulated optimization problems are not convex, and hence, difficult to be
solved directly unless using heuristic methods, which comes at the expense of
high computational complexity.
