Hello everyone, I am Jingxian from Carnegie Mellon. Today I present RFID Tattoo, a wireless
platform for speech recognition.This work is joint with Chengfeng, Haojian, Vaibhav,
Yash, Jason, Carmel and Swarun. There are 7.5 million people in the US who
have trouble using their voice. For example, in this video, she is trying to speak. But
she can not make any sounds. Doctors have different ways for the treatment. Our system
does not focus on that, but we want to provide patients an alternative way to communicate
with others. Indeed, there are many alternative devices
to help people compensate for their voice impairments. For example, a camera equipped
with a lip reading algorithm at the backend can be used to recognize speech. Perhaps,
the most used solution is a specialized keyboard that the patients can use to type every word
they want to say. Also, there is early stage research that infers the intended speech by
sensing the brain signals. As you can see, the current solutions either require external
infrastructure, bulky sensors or manual hand input.
So we present RFID tattoo which is inspired by battery-free RFID tags and temporary tattoos
to provide an everyday intuitive assistive technology for voice impaired patients.This
is our RFID tattoo. It is highly stretchable, and the material is skin-friendly. The key
idea of RFID tattoo is to sense the stretch of the skin as the users make any facial and
tongue movement. It then converts the stretch information into meaningful words. So let’s
see how we infer the skin stretch. The principle we are using is that antenna
length determines the resonant frequency. For example, a 915MHz antenna usually is 8cm
long, and a typical 2.4Ghz antenna is 3 cm long. As you can imagine, a higher frequency
antenna will have a shorter antenna length. The resonant frequency is the frequency where
a given antenna has the best performance. At this frequency, the antenna has the higher
received signal strength than at adjacent frequencies. At a high level, the resonant
frequency of the antenna shifts as the antenna length changes. In this video, we show how
the resonant frequency shifts as we stretch the tattoo. On the left side in the screen,
the red marker shows the resonant frequency. On the right side, we stretch the tattoo.
We can see as we stretch the tattoo, the resonant frequency decreases because the antenna length
of the tattoo increases. In our experiment, we show 1 mm stretch of the tattoo lead to
8 MHz resonant frequency shift. In the previous video, we connected the RFID
tattoo to a VNA to get the resonant frequency. So how can we find the resonant frequency
of the tattoos wirelessly using a commercial RFID reader? A strawman approach is to measure
the received signal strength of the tattoos across the available bandwidth. Basically,
hopping across frequencies and interpolating. As I mentioned, the resonant frequency shifts
as we stretch the tattoo. So at some point, the resonant frequency will shift outside
the ISM band and we can not accurately interpolate that. The available bandwidth of RFID protocol
is just 26 MHz which equals to 3 mm of stretch. However, our facial skin when talking can
stretch as much as tens of mm. Also, according to the Gen2 RFID regulation, when hopping
across the whole ISM band, you need to spend 10 seconds which is too slow.To resolve this
problem, we design an RFID tag embedded with multiple chips that each resonates at different
frequencies. Using this method, we can infer the stretch efficiently. Our system further
resolves additional challenges, for example, multipath, and resolution. Please find more
details in our paper. After we have the stretch information from
multiple tags, we use the stretch information as the feature to apply a machine learning
model to infer the user’s intended speech. From our experiments, we show mm-level stretch
inference. And achieve 86% accuracy in reconstructing
100 words. Thank you so much. Please read our paper for
much more details.