  In this paper, we put forward a proof of concept for sixth generation (6G)
Terabit infrared (IR) laser-based indoor optical wireless networks. We propose
a novel double-tier access point (AP) architecture based on an array of arrays
of vertical cavity surface emitting lasers (VCSELs) to provide a seamless
grid-of-beam coverage with multi-Gb/s per beam. We present systematic design
and thorough analytical modeling of the AP architecture, which are then applied
to downlink system modeling using non-imaging angle diversity receivers (ADRs).
We propose static beam clustering with coordinated multi-beam joint
transmission (CoMB-JT) for network interference management and devise various
clustering strategies to address inter-beam interference (IBI) and
inter-cluster interference (ICI). Non-orthogonal multiple access (NOMA) and
orthogonal frequency division multiple access (OFDMA) schemes are also adopted
to handle intra-cluster interference, and the resulting
signal-to-interference-plus-noise ratio (SINR) and achievable data rate are
derived. The network performance is studied in terms of spatial distributions
and statistics of the downlink SINR and data rate through extensive computer
simulations. The results demonstrate that data rates up to 15 Gb/s are achieved
within the coverage area and a properly devised clustering strikes a balance
between the sum rate and fairness depending on the number of users.
