  Visible light communication (VLC) backscatter has been proposed as a wireless
access option for Internet of Things (IoT). However, the throughput of the
state-of-the-art VLC backscatter is limited by simple single-carrier pulsed
modulation scheme, such as on-off keying (OOK). In this paper, a novel
pixelated VLC backscatter is proposed and implemented to overcome the channel
capacity limitation. In particular, multiple smaller VLC backscatters,
switching on or off, are integrated to generate multi-level signals, which
enables the usage of more advanced modulation schemes than OOK. Based on
experimental results, rate adaptation at different communication distances can
be employed to enhance the achievable data rate. Compared to OOK, the data rate
can be tripled when 8-PAM is used at 2 meters. In general, $n$-fold throughput
enhancement is realized by utilizing $n$ smaller VLC backscatters while
incurring negligible additional energy using the same device space as that of a
single large backscatter.
