Smartphone to smartphone visible light communications

Boubezari, Rayana (2018) Smartphone to smartphone visible light communications. Doctoral thesis, Northumbria University.

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Abstract

Visible light communications (VLC) is an emerging technology of optical wireless communications, which has been in the research spotlight recently, thanks to the remarkable development of light emitting diodes. Furthermore, optical camera communications, a timely VLC topic, has earned a great share of researchers'interest in the last few years, given the wide availability of digital cameras.

This thesis proposes to merge two separate technologies: image processing and VLC, to create a camera-based VLC system. Moreover, the work presented in this thesis describes a short-range mobile-to-mobile communication link, where the transmitter and the receiver are the smartphone’s screen and camera, respectively. In addition, the data is encoded into images and subsequently beamed out of the transmitter's screen, and the receiver's camera captures consecutive frames containing the transmitter's screen to extract the data.

The proposed system offers inherent advantages in terms of portability and simplicity of implementation as it uses available screens and smartphone cameras. Additionally, the system is software-based and does not require any hardware modifications on the devices, thus making a high potential for millions of consumers.

The system proposed in this thesis is designed for mobile users. Therefore, high performance in dynamic environments is required. Moreover, combining image processing and VLC for smartphone to smartphone VLC is an innovative topic and very few works reported similar communication links. As such, it is imperative to investigate the impact of computer vision challenges on the system's performance, such as the detection of the transmitter by the receiver's camera, in dynamic conditions. Consequently, this work focuses on the development of an effective algorithm to capture frames containing the transmitter as well as other objects in the background, detect the transmitter contained in the received frames, and then finally extract the originally transmitted information.

The end-to-end system is fully implemented on a mobile platform and a range of experiments are carried out in order to evaluate the system's performance. It is proved that the system is able to achieve very high success rate that reaches 98% data recovery of transmitted images under test conditions, demonstrating a practical link with a possible 100 kbps data transmission capability.

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