Conformal VLC Receivers with Photodetector Arrays
At the University of Central Florida (UCF), Pooya Nabavi and Murat Yuksei have designed and prototyped a wide field-of-view (FOV) optical receiver to enable visual light communication (VLC) from mobile receivers. They used high brightness low power white LED panels and high-efficiency optical transmitters in the VLC system.
Time-varying inter-symbol interference (ISI) can be a detrimental effect due to the vibration in the structure of the optical receiver as well as its high acceptance angle. An optimal multi-symbol detection (MSD) algorithm was designed and implemented in the structure which greatly decreased the ISI at the cost of exponentially increasing the necessary computation time. To overcome this challenge they designed an adaptive Decision Feedback Affine Projection Algorithm (DF-APA) which reduces the increased computation time from the MSD.
Nabavi and Yuksei tested the VLC system in the presence of intense vibrations in the receiver’s body and were able to achieve a 20 Mbps VLC link over a distance of 7 m. 
VLC vs RF
Compared to the RF systems currently in place, VLC has the potential to be a low-cost, high-throughput and secure form of global wireless communication in space, air, and even underwater. Due to the nature of RF signals radiating in all directions, there is a higher amount of interference between signals. They can also be picked up easily by receivers which are not the intended target which can also pose a security threat for vital data being transmitted. In contrast, VLC can be used in more spatially confined regions and has a lower probability of intercept. VLC also has a higher bandwidth than RF allowing for more data to be transmitted in any given amount of time.
With a limited amount of obstacles, VLC can be an ideal network solution for an indoor communication system. However, in most indoor spaces there are usually many objects which can cause some undesired and detrimental effects even as simple as the movement of a smartphone while it is streaming a video. These operations can cause ISI and therefore limit the effective range and bit rate of an indoor VLC system. Nabavi and Yuskel have further studied the effects of these limiting operations and their detrimental impacts.
Nabavi and Yuskel designed and prototyped a 20 Mbps VLC receiver with a range of 7 meters for indoor office communication. They monitored the performance of the receiver against various adverse effects that introduced ISI. They then developed an optimal MSD algorithm to remedy these adverse effects and increase the system’s BER; however, the algorithm also introduced excess computation time. In response, the group developed a DF-APA to monitor the system’s performance and reduce the excess time from the computation.
- A prototype indoor VLC system for an office environment
- data rates up to 20 Mbps
- 7 m coverage
- BER< 10^-5 in presence of intense vibration in the receiver’s body.
- A multi-photodetector (PD) array VLC receiver design
- conformed to IoT shaped surfaces
- large aggregate receiver surface area for larger FOV and reception range
- Empirical modeling of an indoor VLC channel for a casual office setting
- Formulation of ISI effects on wide FOV receivers in vibrant VLC channels
- consideration of vibration in the environment
- beam divergence angle
- data rate
- link range
- Design of an optimal and adaptive MSD algorithm