  In this paper, we propose joint beamforming and photo-detector (PD)
orientation (BO) optimization schemes for mobile visible light communication
(VLC) with the orientation adjustable receiver (OAR). Since VLC is sensitive to
line-of-sight propagation, we first establish the OAR model and the human body
blockage model for mobile VLC user equipment (UE). To guarantee the quality of
service (QoS) of mobile VLC, we jointly optimize BO with minimal UE the power
consumption for both fixed and random UE orientation cases. For the fixed UE
orientation case, since the {transmit} beamforming and the PD orientation are
mutually coupled, the joint BO optimization problem is nonconvex and
intractable. To address this challenge, we propose an alternating optimization
algorithm to obtain the transmit beamforming and the PD orientation. For the
random UE orientation case, we further propose a robust alternating BO
optimization algorithm to ensure the worst-case QoS requirement of the mobile
UE. Finally, the performance of joint BO optimization design schemes are
evaluated for mobile VLC through numerical experiments.
