1. Communications and Sensing of Illumination Contributions in a Power LED Lighting System Abstract LED technology emerged as a prime candidate for the future illumination light source. LEDs offer a superior flexibility in terms of colors and shapes: immense variety of available light patterns. Patterns creation via easy user interaction requires sensing of local light contribution of each LED. Enabled through tagging of the light of each LED with an unique embedded IDs. To this end, we propose a new modulation and multiple access scheme, named as code-time division multiple access - pulse position modulation (CTDMA-PPM). Our new scheme considers illumination constraints in addition to the communication requirements. Propose system structure, which includes illumination sources, a sensor receiver and a control system. Illumination sources illuminate the environment and transmit information at the same time. This system structure could support a number of luminaries equal to the size of the CDMA codebook times the dimming range. Visible light communications with LEDs over “light link”, allows for: communication of individual data per light source estimation of localized light contributions. Key requirements: Modulation should be invisible and based on pulse-width modulation (PWM) dimming. Jean-Paul Linnartz, Lorenzo Feri, Hongming Yang, Sel Colak and Tim Schenk Intelligent lighting control system Modulation and Multiple Access We propose the CTDMA-PPM scheme: a form of PPM which is keyed according to a spreading sequence, and the duty cycle is subject to PWM light dimming. Description of the binary PPM modulation format. Data is embedded in prefix and inversely in the postfix of PPM block. Identifer: combination of assigned CDMA code γ and start point of the pulse τ. Walsh-Hadamard orthogonal codes are used. Normalized MSE in intensity estimation vs. PD-LED distance. Bit-error rate vs. PD-LED distance for different mode numbers μ of the LEDs. Conclusions Analytical performance results worked out for this scenario. Numerical Results A new modulation and multiple access scheme for power LED systems has been proposed, named CTDMA-PPM, and analyzed. Required performance is achieved up to distances of 10 meters. A very large number of LEDs can be supported in this communications concept. Receiver design Electro-optical conversion in LED has exponential on- and off-switching slopes, with different time constants. Light propagation modeled using generalized Lambertian law. Depends on position of LED and photodiode (PD) and mode number LED μ. Speed PD is much higher than of LEDs. Noise sources are thermal noise and shot noise. Channel model Integrate-and-dump receiver followed by a code despreader. Bit detection using maximum-ratio combiner and threshold detector. Least squares and MMSE intensity estimator designed. N1N1 N2N2 CTDMA-PPM decoding signal structure. Analytical performance results for detection and estimation derived. Scenario: 30 white LEDs/m 2, square grid, 0.5 W optical power/LED. Code length = 256, dimming length 1024, time resolution 1 μs.