Red, green, and blue (RGB) light-emitting diodes (LEDs) are widely used in everyday illumination, particularly where color-changing lighting is required. On the other hand, digital cameras with color filter arrays over image sensors have been also extensively integrated in smart devices. Therefore, optical camera communications (OCC) using RGB LEDs and color cameras is a promising candidate for cost-effective parallel visible light communications (VLC). In this paper, a single RGB LED-based OCC system utilizing a combination of undersampled phase-shift on-off keying (UPSOOK), wavelength-division multiplexing (WDM), and multiple-input-multiple-output (MIMO) techniques is designed, which offers higher space efficiency (3 bits/Hz/LED), long-distance, and nonflickering VLC data transmission. A proof-of-concept test bed is developed to assess the bit-error-rate performance of the proposed OCC system. The experimental results show that the proposed system using a single commercially available RGB LED and a standard 50-frame/s camera is able to achieve a data rate of 150 bits/s over a range of up to 60 m.Index Terms: Optical camera communication (OCC), visible light communications (VLC), non-flickering communication, red, green, and blue (RGB) light-emitting diode (LED), undersampled phase shift on-off keying (UPSOOK), wavelength division multiplexing (WDM), multiple-input-multiple-output (MIMO).

A versatile outdoor and indoor position detection mobile prototype has been successfully constructed and tested. The receiver consists of a GPS module, a GSM shield, a visiblelight data receiver, and two ultrasonic sensors, all controlled by an Arduino Mega and an Arduino Uno microcontroller. Each ultrasonic sensor detects distance in the X and Y axis respectively. The transmitter system consists of four LED shields each attached to an Arduino Uno which is programmed to transmit the global position relevant to the indoor position of the LED lamp. When a person is outdoors, the GPS module receives global position from the satellite. When a person goes indoors, his or her global position will be given by the LEDs and ultrasound sensors. The location data can be transmitted via GSM to a monitoring system or to an individual smartphone. This system is extremely useful in elderly care service. It ensures specific accuracy in locating senior citizens during cases of emergency.

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Based on visible light communication (VLC) technology, three designs of audio transmitters and receivers have been built and tested successfully. The simplicity of these circuits and the very few components that are used enable them to be mass manufactured for use on passenger aircrafts. The receiver circuits can be implemented on headphones. The transmitter circuits can be integrated with LED reading lights above passengers' seats. The circuits presented here have different performance characteristics and sound qualities, depending on the type of audio ICs that are used.

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