WHY HYBRID?
Providing an optical uplink in a VLC system is challenging due to potential energy limitations of mobile devices (that do not otherwise need to produce light for illumination) and potential glare from the produced light.
Also, to be efficient, VLC uplinks will need to use narrow beam widths which lead to challenges due to device motion and orientation with respect to fixed uplink receivers.
Thus VLC remains a strong contender for the downlink channel but is better if complemented with an alternative uplink technology.
