A Fixed-Scale Pixelated MIMO Visible Light Communication System

Abstract

Visible light communication (VLC) systems take advantage of ubiquitous light-emitting diodes (LED) and leverage existing illumination infrastructure to provide broadband optical communication links. Multiple-input multiple-output (MIMO) VLC systems are among the well-studied topics in VLC research. However, most traditional MIMO VLC systems require accurate alignment and have to adjust to different magnifications at various link distances. Consequently, the alignment and calibration modules increase the complexity of the receiver structures.A pixelated MIMO VLC system is introduced in this thesis, which transmits a series of time-varying coded images that can be received and decoded by commercial digital cameras. Using a convex lens placed in front of the transmitter at its focal length, the system exploits the Bokeh effect to obtain fixed-scale images at all link distances.Compared with traditional pixelated MIMO VLC systems, which send information directly in space, this spatial-angular mapping system sends information in different angles instead. In contrast to the complex receiver structures in traditional setups, the proposed system can capture fixed-scale images with a simple receiver requiring no re-focusing as the camera moves. iv The channel model of the system is measured and modeled and a rateless code is applied to track the truncation of receive images for various link ranges and angular offsets. A proof-of-concept optical communication system is implemented with an LCD display and a high speed CMOS camera. Performance of the system is measured and analysed. The experimental system can achieve a throughput of approximately 10 bit per frame over 90 cm. This fixed-scale pixelated MIMO wireless optical communication system provides a less expensive option for short-range indoor broadcasting optical links and intervehicle communications due to its mobility, stability and simpler receiver structure compared to traditional designs in different working conditions. v I would also like to give my warmest thanks to all my colleagues in the research group, especially Mr. Min Lu, who helped me set up the experimental system. Mr.George Su also provided me with a lot of advices on the coding part. Mr. Warren Pawlikowski shared his experience in the hardware area and he has always been a reliable helping hand when I encountered any hardware problem. It is indeed a great honour to work in a group with such diversity and talents.Lastly, I would like to thank my parents for all their love in all these years. They are always my strongest support no matter where I am and how well I am doing.

Optical Camera Communications: Principles, Modulations, Potential and Challenges

“…Since OCC operation is generally bounded by both the LOS path and the limitations of cameras, there are several issues that need addressing: directionality, focusing, alignment and distance. In [90], a pixelated MIMO scheme with a TX (an array of LEDs) fitted with a collimating lens was experimentally investigated for transmission in the angular domain rather than in the space domain. A series of time-varying coded (i.e., Raptor code) images were captured and decoded using a camera, which was focused at infinity, thus achieving a throughput of 30 bit/frame at a link span of 1 m. In addition, this scheme is robust against misalignment, camera focus and orientation.…”

“…Complex modulation schemes (including multi-level and multi-carrier) as well as WDM technologies can be used to increase the data throughput in OCC systems [90,133]. In addition, cameras with increased resolution and the development of more powerful image processing algorithms will enhance the efficiency and robustness of OCC [17,37].…”

Optical camera communications: Survey, use cases, challenges, and future trends

“…The low-priority data was modulated onto the highfrequency components while the high-priority data was modulated on the low-frequency components. The effectiveness of the proposed scheme in [87] In addition to the trend of improving the data rate and transmission distance, efforts are made to improve the system design for OCC, e.g., a spatial-angular modulation technique was developed in [89] by using pixelated MIMO systems to simplify the receiver design. Furthermore, an image sensor with the MIMO technique was used in [90] to reduce the inter-channel interference between the RGB signals.…”

Visible light communication – An architectural perspective on the applications and data rate improvement strategies

“…Furthermore, it was showed that the computation burden of decentralized power allocation algorithms is less when compared with centralized power allocation algorithms. Recently, a fixed‐scale pixelated MIMO VLC was proposed in the work of Han and Hranilovic . The transmitter consists of array of emitters with collimating lens, which enables space to angle mapping of data.…”

“…Recently, a fixed-scale pixelated MIMO VLC was proposed in the work of Han and Hranilovic. 92 The transmitter consists of array of emitters with collimating lens, which enables space to angle mapping of data. Focusing the receiver at infinity, a sequence of time-varying images were captured by a high-speed camera.…”