Visible light communication (VLC) has gained attention recently as radio frequencies become increasingly congested. VLC offers a promising alternative for wireless communication with several advantages: It provides 10 times more bandwidth than traditional radio frequencies, is more energy-efficient and secure, and can take advantage of the existing lighting infrastructure.
However, VLC also has drawbacks, such as its susceptibility to ambient light interference and its dependence on a clear line of sight (LOS). When the receiver is obstructed, such as being placed in a pocket, the signal is blocked, and communication fails.

We address one of the most important NLOS scenarios in VLC: when users place the receiver inside the pocket. Our system places photodiodes on a 3D-printed vest to capture the optical data and then forwards the information to the phone inside the pocket using near-field communication (NFC).

We introduce several optimizations to enhance the performance of LightVest. First, we develop a novel method for optimizing photodiode placement on the vest using the Lambertian propagation model, ensuring optimal angles for maximum signal reception. Additionally, we implement adaptive filtering and threshold techniques to maintain reliable communication in dynamic environments, improving the VLC system's robustness against noise and movement. We also optimize the software to increase the sampling rate, reducing processing times. These improvements result in a maximum data rate of 25 kbps and a range of 220 cm at a data rate of 5 kbps with a bit error rate of 0.025.

We enhanced the NFC link using techniques like Fast Transfer Mode and non-blocking I2C to achieve a maximum data rate of 21 kbps. To facilitate user interaction with the LightVest, we developed an Android application to control the microcontroller. In addition, it provides data visualization and collection, significantly speeding up the debugging and experimentation processes.

Overall, LightVest represents an advancement in extreme NLOS and wearable VLC, paving the way for future innovations in secure and wearable VLC solutions.
Future work could focus on improving the performance of the VLC link by selecting a more powerful microcontroller, using enhanced filtering, and adopting a more advanced modulation scheme. Future efforts could also include adding an uplink to the system to complete the VLC setup and exploring alternative vest designs by using a vest or shirt instead of a 3D model.