25 September 2013 Precoder design for indoor visible light communications with multiple RGB LEDs
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In this paper, we consider the problem of precoder design for an optical intensity modulation (IM) system with multiple redgreen- blue (RGB) light emitting diodes (LEDs) as transmitters and imaging lens with color filters as receivers. The purpose of using a precoder is to optimally allocate power for each LED based on the current channel condition to minimize the detection error rate. To achieve the goal, an non-convex optimization problem due to a nonconvex constraint is formulated first taking into account several crucial lighting constraints, such as flicker-free, color rendering index (CRI), and luminous efficacy rate (LER) as well as the average optical intensity constraint and non-negative transmitter-side signal constraint. By manipulations we transform the problem into a semi-definite programming (SDP) and by approximation we relaxed the non-convex constraint into a convex one. The resulting convex problem is iteratively solved by CVX, an add-in to MATLAB, which jointly optimizes the precoder and DC-biases driving each LED. We assume that M-PAM signal constellation is used as input to the precoder and an MMSE receiver is applied to recover the input signals in this paper, while our method is not restrict to the specific choice.
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Qian Gao, Qian Gao, Tian Lang, Tian Lang, Feng Bo, Feng Bo, Gang Chen, Gang Chen, Yingbo Hua, Yingbo Hua, "Precoder design for indoor visible light communications with multiple RGB LEDs", Proc. SPIE 8874, Laser Communication and Propagation through the Atmosphere and Oceans II, 88740Y (25 September 2013); doi: 10.1117/12.2027180; https://doi.org/10.1117/12.2027180

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