  The emergence of capsule endoscopy has provided a means of capturing video of
the small intestines without having to resort to an invasive procedure
involving intubation. However, real-time video streaming to a receiver outside
the body remains challenging for capsule endoscopy. Traditional
electromagnetic-based solutions are limited in their data rates and available
power. Recently, ultrasound was investigated as a communication channel for
through-tissue data transmission. To achieve real-time video streaming through
tissue, data rates of ultrasound need to exceed 1 Mbps. In a previous study, we
demonstrated ultrasound communications with data rates greater than 30 Mbps
with two focused ultrasound transducers using a large footprint laboratory
system through slabs of lossy tissues [1]. While the form factor of the
transmitter is also crucial for capsule endoscopy, it is obvious that a large,
focused transducer cannot fit within the size of a capsule. Several other
challenges for achieving high-speed ultrasonic communication through tissue
include strong reflections leading to multipath effects and attenuation. In
this work, we demonstrate ultrasonic video communications using a mm-scale
microcrystal transmitter with video streaming supplied by a camera connected to
a Field Programmable Gate Array (FPGA). The signals were transmitted through a
tissue-mimicking phantom and through the abdomen of a rabbit in vivo. The
ultrasound signal was recorded by an array probe connected to a Verasonics
Vantage system and decoded back to video. To improve the received signal
quality, we combined the signal from multiple channels of the array probe.
Orthogonal frequency division multiplexing (OFDM) modulation was used to reduce
the receiver complexity under a strong multipath environment.
