  The visible light communication (VLC) technology has attracted much attention
in the research of the sixth generation (6G) communication systems. In this
paper, a novel three dimensional (3D) space-time-frequency non-stationary
geometry-based stochastic model (GBSM) is proposed for indoor VLC channels. The
proposed VLC GBSM can capture unique indoor VLC channel characteristics such as
the space-time-frequency non-stationarity caused by large light-emitting diode
(LED) arrays in indoor scenarios, long travelling paths, and large bandwidths
of visible light waves, respectively. In addition, the proposed model can
support special radiation patterns of LEDs, 3D translational and rotational
motions of the optical receiver (Rx), and can be applied to angle diversity
receivers (ADRs). Key channel properties are simulated and analyzed, including
the space-time-frequency correlation function (STFCF), received power, root
mean square (RMS) delay spread, and path loss (PL). Simulation results verify
the space-time-frequency non-stationarity in indoor VLC channels. Finally, the
accuracy and practicality of the proposed model are validated by comparing the
simulation result of channel 3dB bandwidth with the existing measurement data.
The proposed channel model will play a supporting role in the design of future
6G VLC systems.
