Colour-shift keying (CSK) has emerged as a new modulation scheme for indoor visible light communication (VLC) systems, standardised in IEEE 802.15.7. This scheme transmits data by modulating the intensity of red-green-blue light-emitting diodes using a colour coding format. To support VLC, CSK requires the application of multiple light sources and detectors without changing the white light target condition. In this study, a low-complexity VLC system is proposed for multiple light sources that offers important reductions to the overall system complexity while maintaining the compatibility with the premises of the IEEE 802.15.7 standard. The contributions of this work are two-fold. First, a new RGB-based modulation scheme is proposed. This modulation scheme suggests to replace the CSK-based colour coding format by a more flexible, versatile and simplified mapping structure without the need of sending target colour information to the receiver. The second contribution is a novel single-photodiode based receiver that reduces the number of inputs to demodulate RGB signals. Closed-form error performance expressions are verified to analyse the proposed VLC system performance which are verified through Monte Carlo simulations. Finally, the performance of the proposed system is also presented and compared in terms of complexity and throughput efficiency.

Color Shift Keying (CSK) is a new modulation scheme for visible light communication systems using RGB LEDs which has been standardized in the PHY III level of the IEEE 802.15.7. This paper proposes some modifications so as to include multiuser capabilities provided by a time-based multiplexing, with the modulation constellation symbols being adapted to encode data with the luminux powers of the red, green and blue color bands respectively. This is achieved by employing a simple and low-complexity time-based pulse signals structure to separate the users' data symbols, while a three-dimensional signal constellation design is merged to improve data throughput. Numerical simulations are carried out to assess the performance of this novel architecture. The statistical properties of the transmitted RGB signals ensure dimming capabilities and that the illumination function is unaffected by flickering.

Abstract:Distance estimation plays an important role in location-based services, which has become very popular in recent years. In this paper, a new short range cricket sensor-based approach is proposed for indoor location applications. This solution uses Time Difference of Arrival (TDoA) between an optical and an ultrasound signal which are transmitted simultaneously, to estimate the distance from the base station to the mobile receiver. The measurement of the TDoA at the mobile receiver endpoint is proportional to the distance. The use of optical and ultrasound signals instead of the conventional radio wave signal makes the proposed approach suitable for environments with high levels of electromagnetic interference or where the propagation of radio frequencies is entirely restricted. Furthermore, unlike classical cricket systems, a double-way measurement procedure is introduced, allowing both the base station and mobile node to perform distance estimation simultaneously.

In color-multiplexed optical camera communications (OCC) systems, data acquisition is restricted by the image processing algorithm capability for fast source recognition, regionof-interest (ROI) detection and tracking, packet synchronization within ROI, estimation of inter-channel interference and threshold computation. In this work, a novel modulation scheme for a practical RGB-LED-based OCC system is presented. The four above-described tasks are held simultaneously. Using confined spatial correlation of well-defined reference signals within the frame's color channels is possible to obtain a fully operating link with low computational complexity algorithms. Prior channel adaptation also grants a substantial increase in the attainable data rate, making the system more robust to interferences.

This paper explores the use of a reading lamp as an access point for a Visible Light Communications (VLC) downlink channel. We have established an infrared uplink channel based on a network adapter, supporting both a VLC receiver and an infrared emitter. The optical signal power distribution over the passenger area has been also studied using a Monte Carlo Ray-Tracing algorithm. The hardware implementation and testing results are also presented. 1