Experimental Demonstration of a Visible Light Communications System Based on Binary Frequency-Shift Keying Modulation: A New Step toward Improved Noise Resilience

Abstract

Visible light communications (VLC) are an emerging technology that is increasingly demonstrating its ability to provide wireless communications in areas where radio frequency (RF) technology might have some limitations. Therefore, VLC systems offer possible answers to various applications in outdoor conditions, such as in the road traffic safety domain, or even inside large buildings, such as in indoor positioning applications for blind people. Nevertheless, several challenges must still be addressed in order to obtain a fully reliable solution. One of the most important challenges is focused on further improving the immunity to optical noise. Different from most works, where on–off keying (OOK) modulation and Manchester coding have been the preferred choices, this article proposes a prototype based on a binary frequency-shift keying (BFSK) modulation and non-return-to-zero (NRZ) coding, for which the resilience to noise is compared to that of a standard OOK VLC system. The experimental results showed an optical noise resilience improvement of 25% in direct exposure to incandescent light sources. The VLC system using BFSK modulation was able to maintain a maximum noise irradiance of 3500 µW/cm2 as compared with 2800 µW/cm2 for the OOK modulation, and an improvement of almost 20% in indirect exposure to the incandescent light sources. The VLC system with BFSK modulation was able to maintain the active link in an equivalent maximum noise irradiance of 65,000 µW/cm2, as opposed to the equivalent 54,000 µW/cm2 for the OOK modulation. Based on these results, one can see that based on a proper system design, VLC systems are able to provide impressive resilience to optical noise.

Driving toward Connectivity: Vehicular Visible Light Communications Receiver with Adaptive Field of View for Enhanced Noise Resilience and Mobility

“…Later on, as the design of VLC receivers improved, better tradeoff solutions were integrated. Thus, today's vehicular VLC receivers commonly have ±20 • FoVs [21,[24][25][26], while sometimes reaching ±50 • [25]. Nevertheless, wide FoV VLC receivers are not able to maintain an active link under sunlight conditions, or they may only be able to provide limited communication ranges.…”

“…This aspect was pointed out by the authors of [38,39], who intensively investigated the benefits of the direct sequence spread spectrum (DSSS) technique. Their experiments showed that such a system can deal with daylight noise and can enable communication ranges of up to 40 m. The authors of [21] experimentally demonstrated that noise resilience can be improved with the help of binary phase shift keying (BPSK) modulation. This approach enabled the VLC system to better filter the noise, improving the resilience to optical interference by 25% compared to the use of the classical on-off keying (OOK) modulation.…”

“…Regardless of these unfriendly conditions, VLC has made impressive progress, achieving a performance that was difficult to imagine before. Thus, today's vehicular VLC prototypes can provide a high resilience to optical interference [19][20][21], including the interference generated by multiple VLC transmitters [22]; decent data rates; and communication ranges of up to almost 200 m [23], indicating that this technology is almost ready for real-life implementation [24][25][26]. Although substantial strides have been made in advancing vehicular VLC technology, its specific challenges require further research efforts.…”

Visible Light Communications-Based Assistance System for the Blind and Visually Impaired: Design, Implementation, and Intensive Experimental Evaluation in a Real-Life Situation

“…Thus, it is important to emphasize that the system is designed to be compatible with light dimming, making it suitable for energysaving applications while maintaining its blind assistance functions. For situations that imply high optical noise, the concept is also compatible with Binary Frequency-Shift Keying (BFSK) modulation [38], solution that further enhances the system's resilience to noise. In its turn, the VLC receiver represents a vital component of the smart backpack.…”

Study on Optical Positioning Using Experimental Visible Light Communication System

“…Indeed, similar to the Global Positioning System (GPS), which is widely used in outdoor environments, visible light positioning (VLP) can provide the navigation information to find the target indoor destinations. It can therefore be utilized inside large buildings such as for asset tracking in hospitals or universities, for indoor positioning applications for blind people, as well as to provide location-aware services, such as antique information in museums or item prices in shopping malls [11,12].…”