Multiuser Detection for Sensing Asynchronous LED Illumination Contributions

Master thesis (2010)

Authors

Contributors

G. Leus (mentor)
A. Van der Veen (mentor)
Department
Telecommunications (EEMCS) (TU Delft)
Copyright: © 2010 Liu, D.
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Published Date

22-04-2010

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Faculty

Electrical Engineering, Mathematics and Computer Science

Department

Telecommunications

Abstract

In recent years, light-emitting diodes (LEDs) have played an increasingly more important role for light illumination. Beyond the basic function of pure illumination via intensity control of xed color light, LED technology additionally allows control over the light color and illumination pattern. In order to realize these functions of intelligent lighting control, we need to estimate the light intensity of each LED in the sensor location. To this end, a synchronous code-time division multiple access - pulse width modulation (CTDMA-PWM) system has been proposed for LED identification and simultaneous measurement of illumination strength. However, this system strictly requires perfect synchronization, which in practice is not easy to be guaranteed. Therefore, in this thesis, we propose an asynchronous CTDMA-PWM scheme and corresponding multiuser detection algorithm to combat the multiple access interference (MAI) caused by asynchronous multiple access. We explore the algorithm of conventional minimum mean square error (MMSE) linear estimation and implement it iteratively in a blind way without the knowledge of channel input from interfering LEDs.