  Optical wireless communication (OWC) is considered to be a promising
technology which will alleviate traffic burden caused by the increasing number
of mobile devices. In this study, a novel vertical-cavity surface-emitting
laser (VCSEL) array is proposed for indoor OWC systems. To activate the best
beam for a mobile user, two beam activation methods are proposed for the
system. The method based on a corner-cube retroreflector (CCR) provides very
low latency and allows real-time activation for high-speed users. The other
method uses the omnidirectional transmitter (ODTx). The ODTx can serve the
purpose of uplink transmission and beam activation simultaneously. Moreover,
systems with ODTx are very robust to the random orientation of a user equipment
(UE). System level analyses are carried out for the proposed VCSEL array
system. For a single user scenario, the probability density function (PDF) of
the signal-to-noise ratio (SNR) for the central beam of the VCSEL array system
can be approximated as a uniform distribution. In addition, the average data
rate of the central beam and its upper bound are given analytically and
verified by Monte-Carlo simulations. For a multi-user scenario, an analytical
upper bound for the average data rate is given. The effects of the cell size
and the full width at half maximum (FWHM) angle on the system performance are
studied. The results show that the system with a FWHM angle of $4^\circ$
outperforms the others.
