Design and Analysis of LCD-Based Modulator for Passive Sunlight Communications

Abstract

Solar energy is widely used for electricity generation, heating systems, and indoor environment daytime illumination. Indeed, large amounts of sunlight energy remain insufficiently used. In this work, we aim at employing sunlight energy for data transmission as a green option for wireless communications. Being emitted by an uncontrollable source, taming the sunlight is a challenging task that requires appropriate technologies to manipulate incident light. Liquid crystal devices are switchable glass technologies that have adequate response time and contrast characteristics for such an application. In this regard, we design a novel dual-cell liquid crystal shutter (DLS) by stacking two liquid crystal cells that operate in opposite manners, and we build our sunlight modulator with an array of DLSs. Then, we adopt time division multiplexing and polarization-based modulation to boost the data rate and eliminate the flickering effect. In addition, we provide mathematical modeling of the system and study its performance in terms of communication and energy consumption. Finally, we introduce some numerical results to examine the impact of multiple parameters on the system's performance and compare it with the state-of-the-art, which showed that our system features higher data rates and extended link ranges.

Optical Wireless Communications: Illuminating the Path for Cooper's Law

“…In general, both electrochromic devices and suspended particle devices suffer from slow switching and limitations on contrast between clear and dark states, which limits their applicability in wireless communications applications [102]. On the other hand, LCDs and MEMS-based micro-shutters could achieve switching times in orders of tens of microseconds and high contrast, where the former offers a higher energy efficiency [103], [104]. Reliance on LCD technologies has been receiving an increasing interest for applications such as backscatter communications [105]- [108] and sunlight modulation [34], [103], [109], [110].…”

“…On the other hand, LCDs and MEMS-based micro-shutters could achieve switching times in orders of tens of microseconds and high contrast, where the former offers a higher energy efficiency [103], [104]. Reliance on LCD technologies has been receiving an increasing interest for applications such as backscatter communications [105]- [108] and sunlight modulation [34], [103], [109], [110]. In [105], [106], bi-directional VLC was realized by backscattering using retro-reflector and modulating via an LCD shutter the LED downlink transmission to facilitate uplink transmission, while [107] varied switching time and polarization to establish a backscatter link using an LCD array.…”

“…Moreover, the dual use of existing infrastructure (e.g., utilizing LED-based lighting for both illumination and data transmission) presents opportunities for reducing power consumption and lowering cost of deployment [32]. Also, the growing interest in utilizing elements such as windows and solar cells for the purposes of transferring data offers opportunities to further enhance the resource utilization efficiency and support the energy and environmental sustainability goals [33], [34].…”

550 m low-power outdoor visible light communication system using polarized light

“…Polarization has also been explored for short-range indoor communication using multi-colored LEDs 9 and to encode data on daylight coming in through an office window. 10 These studies provided communication at ranges of 4 m and 7.5 m, respectively. While valuable in their applications, these studies are far short of meaningful vehicular-VLC, which was suggested as a follow-on application in Ref.…”

“…While valuable in their applications, these studies are far short of meaningful vehicular-VLC, which was suggested as a follow-on application in Ref. 10. In spite of signal attenuation per inverse squared law and significant solar noise, polarization of light is unaffected by turbulence along the propagation path.…”